How to Measure Windows for Curtains and Blinds the Right Way
Measuring your windows sounds simple until you are standing there with a tape measure, wondering whether to measure the glass, the frame, the molding, the wall space, or the height from the ceiling.
I see this all the time with clients in New York homes and apartments. A window may look standard at first glance, but once we start measuring, we often find uneven frames, radiator covers, deep sills, shallow window pockets, crown molding, tilt and turn windows, air conditioners, or very little wall space on one side.
That is why proper measuring matters so much.
The right measurements help your curtains hang beautifully, your blinds fit cleanly, and your shades operate smoothly. The wrong measurements can lead to gaps, dragging fabric, crooked lines, light leaks, or custom products that simply do not fit.
In this guide, I will walk you through exactly how to measure windows for curtains and blinds, how to understand width versus height, when to choose inside mount versus outside mount, what tools you need, and when it is better to call a professional.
If you are planning a full design project, you can also explore our custom curtains and drapes to see how the right measurements turn into a finished look that feels tailored, soft, and intentional.
Quick Answer How Do You Measure Windows for Curtains and Blinds?
To measure windows for curtains, measure the width of the area you want the curtain rod to cover, then multiply that width by about 1.5 to 2.5 for fabric fullness. For height, measure from the curtain rod position to the point where you want the curtains to end, such as the sill, below the sill, or the floor.
To measure windows for blinds or shades, first decide between inside mount and outside mount. For inside mount, measure the width at the top, middle, and bottom of the window opening, then use the narrowest width. Measure height at the left, center, and right, then use the tallest height. For outside mount, measure the full area you want the blind or shade to cover and add extra width and height for better light control.
Before You Start Understand Width Versus Height
The two measurements that matter most are width and height, but they are used differently depending on whether you are measuring for curtains, blinds, or shades.
| Measurement | What It Means | Why It Matters |
|---|---|---|
| Width | The side to side measurement | Controls coverage, fullness, light gaps, privacy, and how wide the finished treatment looks |
| Height | The top to bottom measurement | Controls where the treatment starts, where it ends, and how polished the final proportions look |
| Depth | The front to back space inside the window frame | Important for inside mount blinds and shades |
For curtains, width is mostly about coverage and fullness. For blinds and shades, width is about fit and function. A half inch can make a big difference, especially with inside mount products.
Tools You Need to Measure Windows
You do not need many tools, but you do need the right ones.
| Tool | Why You Need It |
|---|---|
| Steel tape measure | More accurate than a soft sewing tape |
| Pencil or notes app | To record each measurement clearly |
| Step stool or ladder | Needed for tall windows or high rod placement |
| Level | Helpful when checking uneven trim or planned rod height |
| Paper sketch | Useful when measuring several windows in one room |
| Phone camera | Helps document obstacles like radiators, handles, molding, or AC units |
My advice is simple. Never rely on memory. Write every measurement down immediately, and label each window by room and wall.
For example:
Living Room Window 1
Bedroom Left Window
Dining Room Bay Window Center Panel
This prevents confusion later, especially if you have multiple windows that look similar but are not exactly the same size.
Step 1 Decide What You Are Measuring For
Before you measure, decide what type of window treatment you want.
Curtains and drapes are measured differently from blinds and shades. A soft fabric panel needs room to stack on the wall, hang properly, and create fullness. A blind or shade needs a precise fit so it can raise, lower, tilt, and cover the glass correctly.
Here is the simplest way to think about it.
| Product Type | Most Important Measurement Goal |
|---|---|
| Curtains | Beautiful proportions, fullness, and height |
| Drapes | Tailored coverage, length, lining, and stack space |
| Blinds | Accurate fit, slat operation, privacy, and light control |
| Shades | Clean fit, smooth operation, and minimal light gaps |
| Motorized treatments | Exact measurements plus power, controls, and clearance planning |
If you are still choosing between options, our guide to custom blinds is a helpful place to start, especially if you want a structured look with strong light control.
Step 2 Decide Between Inside Mount and Outside Mount
Inside mount and outside mount are two of the most important measuring decisions.
What Is Inside Mount?
Inside mount means the blind or shade sits inside the window opening.
This creates a clean, built in look. It is especially popular for roman shades, roller shades, solar shades, wood blinds, faux wood blinds, and woven shades.
Inside mount works best when the window frame has enough depth and the opening is reasonably square.
What Is Outside Mount?
Outside mount means the blind, shade, curtain, or drape is installed outside the window opening, usually on the wall, trim, or ceiling.
This is useful when the frame is too shallow, uneven, or when you want better privacy and light control.
Outside mount can also make a window look larger and more elegant, which is why we often use it in New York apartments where the architecture needs a little visual lift.
| Mount Type | Best For | Main Benefit |
|---|---|---|
| Inside mount | Clean frames, deeper window openings, modern interiors | Sleek built in look |
| Outside mount | Shallow frames, uneven windows, better blackout, larger visual effect | More coverage and flexibility |
Step 3 How to Measure for Curtains
Curtains are more forgiving than blinds, but they still need thoughtful measurements. The most common mistake I see is measuring only the window glass. For curtains, you usually want to measure the area the fabric will cover, not just the glass.
Measure Curtain Width
Start by deciding where the curtain rod will go.
A good general rule is to extend the rod beyond the window frame on both sides. This allows the curtains to frame the window instead of blocking too much glass when open.
For many windows, I like to extend the rod about 6 to 12 inches beyond the window on each side when space allows. In smaller rooms or tight city apartments, we may use less. In larger rooms, tall windows, or luxury drapery projects, we may use more.
To calculate curtain width:
| Step | What to Do |
|---|---|
| 1 | Measure the full rod width from left end to right end |
| 2 | Multiply that number by 1.5 for light fullness |
| 3 | Multiply by 2 for a fuller designer look |
| 4 | Multiply by 2.5 for a rich, luxurious look |
Example:
If your rod width is 100 inches, your total curtain fabric width should usually be about 200 inches for a full look.
That does not mean each panel is 200 inches. It means both panels together should provide that total fabric width.
Measure Curtain Height
Curtain height depends on where you place the rod and where you want the fabric to end.
In most rooms, curtains look better when the rod is placed above the window frame, not directly on top of it. This makes the window look taller and the room feel more finished.
A common starting point is 4 to 6 inches above the window frame, but in many design projects, we go closer to the ceiling for a more elevated look.
| Curtain Length Style | Where to Measure To | Best For |
|---|---|---|
| Sill length | Bottom of the window sill | Kitchens, bathrooms, casual rooms |
| Apron length | A few inches below the sill | Traditional rooms or windows with obstacles below |
| Floor length | Just above the floor | Clean, tailored, modern look |
| Slight break | Fabric lightly touches the floor | Soft designer look |
| Puddle | Extra fabric rests on the floor | Formal or romantic interiors |
For most homes, I recommend floor length curtains that stop just above the floor or lightly touch it. This looks clean, intentional, and easy to maintain.
If you want a more finished designer look, custom drapes and curtains are worth considering because the length, fullness, lining, and hardware are all planned together.
Step 4 How to Measure Windows for Blinds
Blinds need more precise measurements than curtains because they must fit and operate correctly.
Before measuring, choose inside mount or outside mount.
How to Measure Inside Mount Blinds
For inside mount blinds, measure inside the window opening.
Measure width in three places:
| Width Measurement | Where to Measure |
|---|---|
| Top width | Inside left edge to inside right edge at the top |
| Middle width | Inside left edge to inside right edge in the middle |
| Bottom width | Inside left edge to inside right edge at the bottom |
Use the narrowest width.
This matters because many windows are not perfectly square. If the top is 34 inches, the middle is 33.75 inches, and the bottom is 34 inches, the blind needs to be based on 33.75 inches so it can fit without rubbing.
Now measure height in three places:
| Height Measurement | Where to Measure |
|---|---|
| Left height | Inside top edge to inside sill on the left |
| Center height | Inside top edge to inside sill in the center |
| Right height | Inside top edge to inside sill on the right |
Use the tallest height.
Also measure the window depth. This is the front to back space inside the frame. Depth determines whether the blind can sit fully recessed or whether it may project slightly beyond the frame.
How to Measure Outside Mount Blinds
For outside mount blinds, measure the full area you want the blinds to cover.
Outside mount gives you more flexibility and better coverage. It is often the better choice when you want to reduce side light gaps or cover imperfect trim.
A common approach is to add extra width on both sides of the window opening. This helps the blind overlap the wall or trim and improves privacy.
| Measurement | What to Do |
|---|---|
| Width | Measure the window opening, then add coverage on both sides |
| Height | Measure from the top mounting point to where the blind should end |
| Clearance | Check handles, locks, molding, radiators, and furniture |
For blackout needs, outside mount is often more effective because it allows the treatment to cover more of the window area.
Step 5 How to Measure for Shades
Shades are measured very similarly to blinds, but the product style matters.
Roller shades, solar shades, roman shades, cellular shades, woven wood shades, and blackout shades all have different hardware and fabric behavior.
For inside mount shades, measure the inside width at the top, middle, and bottom, then use the narrowest width. Measure inside height at the left, center, and right, then use the tallest height.
For outside mount shades, measure the full area you want to cover and add extra width and height where possible.
The more exact you are, the cleaner the shade will look.
If you are choosing shades for light control, privacy, or a softer modern look, our custom window shades page explains popular options and where each style works best.
Step 6 How to Measure for Motorized Window Treatments
Motorized treatments need the same width and height measurements, but there are extra details to think about.
You also need to consider power access, battery placement, remote controls, smart home integration, headrail size, and whether the treatment has enough room to move without hitting handles, furniture, or molding.
This is especially important for tall windows, hard to reach windows, large glass doors, and homes with multiple treatments in the same room.
When we install motorized window treatments in New York homes, measurement is only one part of the planning. We also think about how the client will actually live with the system every day. That includes morning light, evening privacy, glare on screens, child safety, and whether the room needs one control zone or several.
How to Size Curtains Correctly
Sizing curtains is about more than covering the window. It is about proportion.
A curtain that is too narrow will look flat and unfinished. A curtain that is too short can make the room feel awkward. A rod that is placed too low can make the ceiling feel lower.
Here is a simple sizing guide.
| Area | Designer Recommendation |
|---|---|
| Rod width | Wider than the window when wall space allows |
| Fabric fullness | Usually 1.5 to 2.5 times the rod width |
| Rod height | Above the window frame or closer to the ceiling for a taller look |
| Curtain length | Usually floor length for living rooms, bedrooms, and dining rooms |
| Panel stack | Leave enough side space so fabric does not block too much glass |
For a high end look, I usually prefer curtains that are mounted higher and wider than the window. This makes the glass feel bigger, lets in more natural light when the panels are open, and gives the room a more custom feel.
How to Measure Windows With Trim or Molding
Trim can change the way you measure.
For inside mount blinds or shades, measure inside the window opening, not across the outer trim.
For outside mount blinds or shades, you may measure across the trim or beyond the trim, depending on where the treatment will be installed.
For curtains, the rod usually sits outside and above the trim, so measure the full rod width and the full finished height.
If your trim is decorative, uneven, very narrow, or unusually deep, outside mount may be the better option.
How to Measure Bay Windows and Corner Windows
Bay windows and corner windows require more planning because each treatment must fit without colliding with the next one.
Measure each section separately. Do not assume all sides of the bay are the same size.
For bay windows, note the angles between window sections. For corner windows, check whether the treatments will meet in the corner, overlap, or need separate mounting space.
This is one of those situations where a professional measurement can save a lot of frustration. A bay window can be beautiful with roman shades, woven shades, tailored drapes, or layered treatments, but only when the measurements and hardware are planned correctly.
How to Measure Sliding Glass Doors
Sliding doors need both coverage and function.
Measure the full width of the door area, including the frame. Then decide whether the treatment should stack to one side, split in the middle, or cover the full opening from above.
For curtains, measure the rod width beyond the door frame if space allows. This lets the fabric move off the glass when open.
For vertical treatments, panel tracks, or large roller shades, measure the exact width and height of the opening and check for handles, locks, floor transitions, baseboards, and ceiling height.
Sliding doors are also a great place to consider motorization, especially when the opening is wide or used every day.
Common Measuring Mistakes to Avoid
Measuring mistakes are more common than people think. Here are the ones I see most often.
| Mistake | Why It Causes Problems |
|---|---|
| Measuring only the glass | Most treatments need the frame, opening, wall space, or rod width |
| Rounding measurements | Custom treatments need exact measurements |
| Measuring one spot only | Windows are often uneven from top to bottom |
| Forgetting depth | Inside mount blinds and shades may not fit properly |
| Choosing inside mount for shallow frames | The product may stick out or not install securely |
| Hanging curtains too low | The room can feel shorter and less polished |
| Ordering curtains without fullness | Panels can look flat and inexpensive |
| Ignoring obstacles | Handles, radiators, AC units, molding, and furniture can interfere |
| Measuring all windows as identical | Similar windows can still vary by small but important amounts |
| Not considering light gaps | Inside mount products may allow more light at the sides |
One of my biggest tips is to measure twice, then measure again on a different day if you are ordering custom products yourself. It sounds simple, but it can prevent expensive mistakes.
Inside Mount Versus Outside Mount Which One Should You Choose?
Choose inside mount if you want the cleanest look and your window has enough depth.
Choose outside mount if you want better coverage, stronger blackout, more flexibility, or if your window frame is shallow or uneven.
| Choose Inside Mount When | Choose Outside Mount When |
|---|---|
| You want a sleek built in look | You want to make the window look larger |
| The frame has enough depth | The frame is shallow or uneven |
| You like visible trim | You want to cover trim or gaps |
| Light gaps are not a major concern | You want better privacy or blackout |
| The window is square enough | The window has measurement issues |
There is no one right answer for every home. In many projects, we use inside mount shades with outside mount drapes layered over them. This gives you function during the day and softness at night.
How Much Extra Width Should Curtains Have?
For curtains, the extra width comes from two places.
First, the rod should usually extend beyond the window frame. Second, the fabric itself should be wider than the rod so it hangs with fullness.
A simple formula is:
Total curtain fabric width equals rod width multiplied by 1.5 to 2.5.
| Look | Fullness Multiplier |
|---|---|
| Simple and light | 1.5 times rod width |
| Full and balanced | 2 times rod width |
| Rich and luxurious | 2.5 times rod width |
For most homes, 2 times fullness is a good target. It gives the curtains enough body without feeling overly heavy.
How High Should Curtains Be Hung?
Curtains usually look best when they are hung above the window frame.
In many rooms, hanging the rod 4 to 6 inches above the window works well. For a more dramatic look, especially with higher ceilings, hang the rod closer to the ceiling.
The goal is to make the window feel taller and the room feel more refined.
Avoid placing the rod directly on the window frame unless there is a design reason or limited space.
How Long Should Curtains Be?
The best curtain length depends on the room and the style you want.
For living rooms, bedrooms, dining rooms, and primary spaces, floor length is usually the most elegant option.
For kitchens, bathrooms, and windows above built in furniture, sill length or apron length may be more practical.
| Room | Recommended Curtain Length |
|---|---|
| Living room | Floor length or slight break |
| Bedroom | Floor length, often with blackout lining |
| Dining room | Floor length for a finished look |
| Kitchen | Sill length or cafe style depending on layout |
| Bathroom | Sill length or moisture friendly treatment |
| Nursery | Floor length with safe hardware and cordless options |
How to Measure for Layered Window Treatments
Layered window treatments are one of my favorite ways to finish a room.
A common combination is an inside mount shade with outside mount drapes. The shade gives privacy and light control, while the drapes add softness, texture, and warmth.
For layered treatments, measure each layer separately.
| Layer | What to Measure |
|---|---|
| Inside shade | Inside width, inside height, and depth |
| Drapery rod | Full desired rod width |
| Drapery height | Rod position to finished length |
| Wall space | Side stack space for fabric |
| Obstacles | Molding, sconces, radiators, furniture, AC units |
Layering is where custom work really matters because every detail affects the final result.
When to Call a Professional
You can measure simple windows yourself, especially for basic ready made curtains. But for custom blinds, shades, drapes, bay windows, motorized systems, or expensive fabrics, I strongly recommend professional measuring.
Call a professional when:
| Situation | Why Professional Help Matters |
|---|---|
| You are ordering custom treatments | Mistakes can be costly |
| Your windows are uneven | A pro knows which measurement to use |
| You want blackout | Mounting and overlap must be planned carefully |
| You have bay or corner windows | Angles and hardware spacing matter |
| You have very tall windows | Safety and installation planning are important |
| You want motorization | Measurements, wiring, controls, and clearance all matter |
| You are layering treatments | Each layer must work together |
| You are unsure about style | A designer can help with proportion, fabric, color, and function |
In my experience, the best window treatments start with the conversation before the measurement. How do you use the room? Do you need privacy during the day? Do you get glare on a TV or computer screen? Do you want the room to feel softer, taller, darker, warmer, or more finished?
Those answers change the measurement plan.
Professional Measuring Versus DIY Measuring
DIY measuring can work well for simple projects, but professional measuring gives you more confidence when the result needs to be exact.
| Option | Best For | Main Limitation |
|---|---|---|
| DIY measuring | Simple curtains, basic windows, budget updates | Higher risk of fit or style issues |
| Professional measuring | Custom blinds, shades, drapes, motorized treatments, complex windows | Requires an appointment |
A professional does not just measure width and height. We look at the whole window condition, mounting surface, hardware placement, room style, privacy needs, light direction, and installation details.
That is how you get a result that feels intentional instead of just functional.
FAQs About Measuring Windows for Curtains and Blinds
Do I measure the window or the wall for curtains?
For curtains, you usually measure the area the curtain rod will cover, not just the window glass. The rod often extends beyond the window frame on both sides to create a fuller and more elegant look.
How do I measure windows for curtains?
Measure the desired rod width first. Then measure from the planned rod height to the point where you want the curtains to end. For fabric fullness, multiply the rod width by about 1.5 to 2.5.
How do I size curtains correctly?
Curtains should usually be wider than the window and long enough to feel intentional. For most rooms, floor length curtains with about 2 times fabric fullness create a polished designer look.
Should curtains touch the floor?
In living rooms, bedrooms, and dining rooms, curtains usually look best when they just touch the floor, hover slightly above it, or create a soft break. Short curtains can work in kitchens, bathrooms, or windows with furniture underneath.
How do I measure windows for blinds?
For inside mount blinds, measure the inside width at the top, middle, and bottom, then use the narrowest width. Measure the inside height at the left, center, and right, then use the tallest height. For outside mount blinds, measure the full coverage area you want the blind to cover.
What is the difference between inside mount and outside mount?
Inside mount means the treatment fits inside the window frame. Outside mount means it is installed outside the frame, usually on the wall, trim, or ceiling. Inside mount looks cleaner, while outside mount often gives better coverage and light control.
Should blinds be exact width?
Inside mount blinds need very accurate measurements because they must fit inside the opening. Outside mount blinds can be wider than the window opening for better coverage and privacy.
How much wider should blinds be for outside mount?
It depends on the window and product type, but outside mount blinds are usually measured wider than the opening to reduce light gaps and improve privacy. The exact added width should be based on your frame, wall space, and style goals.
Can I use the same measurements for all windows in a room?
Not always. Even windows that look identical can vary slightly. Measure every window separately, especially when ordering custom products.
What if my window is not square?
Use multiple measurements. For inside mount blinds and shades, use the narrowest width and tallest height. If the window is very uneven, outside mount may be a better choice.
Is it worth getting professional measurements?
Yes, especially for custom blinds, shades, drapes, motorized treatments, bay windows, tall windows, and blackout projects. Professional measuring helps avoid costly mistakes and creates a cleaner finished result.
Final Thoughts From Moria
Measuring your windows is the first step toward window treatments that truly fit your home. But the best result comes from more than numbers. It comes from understanding how the room works, how the light moves, how much privacy you need, and what style will make the space feel complete.
A beautiful curtain, blind, or shade should look like it belongs there. It should feel balanced with the architecture, easy to use, and right for the way you live.
If you are not sure where to start, I would be happy to help.
Free In Home Consultation
Alluring Window offers free in home consultations for custom curtains, drapes, blinds, shades, and motorized window treatments.
We will measure your windows, review your options, help you choose the right style, and make sure every detail is planned before anything is ordered.
Schedule your free in home consultation with Alluring Window today and let us help you create window treatments that fit beautifully, function smoothly, and elevate your home.
