How to Measure Your Windows for New Shades
Measuring windows for new shades takes about ten minutes per window, and getting it right matters more than any other step. A shade that is a quarter of an inch too wide will not fit, and one that is too narrow lets light leak at the sides. This guide walks through how to measure for both mount types, what tools to use, which mistakes cause most remakes and when it makes sense to let a professional do it.
What you need before you start
Use a steel tape measure, not a cloth sewing tape. A steel tape stays straight and does not stretch, so your numbers hold up. You will also need a pencil, paper or your phone for notes and a small ladder for tall windows. Measure each window separately, even when the windows look identical. Houses settle, and two windows side by side can differ by a quarter of an inch or more.
Choose inside mount or outside mount first
Everything else depends on this choice. An inside mount sits inside the window frame, which gives a clean, built in look and leaves the trim visible. An outside mount sits on the wall or trim above the window and covers the opening, which hides uneven frames and blocks more light around the edges.
An inside mount needs enough depth in the frame for the brackets and for the shade to sit properly. Depth requirements differ between products, so check the one for the shade you are considering. If the frame is too shallow, an outside mount is the better choice. If you like the look of a clean frame but want the best light control, ask about options before you decide. Our guide to what cellular shades are explains how different shades fit and behave.
How to measure for an inside mount
- Measure the width in three places. Take the width at the top, the middle and the bottom of the frame, from one inside edge to the other. Write down all three numbers. Use the narrowest one, because that is the width the shade has to fit through.
- Measure the height in three places. Take the height at the left, the center and the right side, from the top of the frame to the sill. Many shade makers ask for the longest height. Follow the instructions of the product you order.
- Measure the depth. Measure from the front of the frame to the first obstruction, such as the window glass, a handle or a crank. Compare the number with the depth the shade needs.
- Write down exact numbers. Record them to the nearest eighth of an inch. Do not round down and do not subtract anything yourself unless the instructions tell you to. The manufacturer usually makes the small allowance needed for a good fit.
How to measure for an outside mount
For an outside mount, measure the area you want to cover instead of the opening itself. Measure the width of the area, then the height from where the shade will start to where it should end. Add a few inches of overlap on each side of the window so the shade blocks light around the edges and the window looks larger. If you want the shade to reach the sill or the floor, measure to that point.
Check what is on the wall where the brackets will go. Trim, a ceiling beam or a light switch can limit where you can mount the shade. Mark the spots lightly with a pencil before you order.
Always write width first
Order forms ask for width first and then height. Mixing them up is one of the most common ordering mistakes and is easy to avoid. Write your notes in the same order every time, for example room, window name, mount type, width, height and depth.
Special windows and doors
- Sliding doors: note the handle and the track, because they can interfere with a shade mounted inside. Many people choose an outside mount above the door.
- Bay windows: measure each section on its own and note the angles between them. This job is easier with a second person.
- Arched and angled windows: these usually need custom shapes, so measure carefully and take photos.
- Tall or hard to reach windows: motorized shades are common here, and they need room for the motor and the power source. Our guide on whether motorized shades are worth it shows which windows benefit most.
Common measuring mistakes
- Using a cloth tape or a tape that bends.
- Assuming the window is square and measuring only once.
- Rounding numbers down or subtracting an allowance that the maker already adds.
- Forgetting handles, cranks, latches and trim that stick out.
- Measuring through the glass edge instead of the frame.
- Mixing up width and height on the order form.
Measure once, then check it again
After you have all the numbers, measure each window a second time on a different day. If the two readings match, you are ready to order. If they differ, measure a third time and look for what changed. A few minutes of rechecking costs less than remaking a custom shade. Custom shades are made to your numbers, so the result depends on the accuracy of what you send.
When to let a professional measure
Measuring is manageable for standard windows, but some jobs are better left to someone who does it every day. Large windows, bay windows, sliding doors, arched shapes and motorized shades all leave less room for error. Shade.Shop measures for free, and a measuring visit also helps you compare mount types and see how colors and light control look in your rooms. To see what a project can cost, read our guide to what motorized shades cost.
If you plan to install the shades yourself once they arrive, our step by step guide on how to hang cellular shades covers the tools, the brackets and the final checks. For help choosing styles that work together across rooms, see should all my window shades match.
Frequently asked questions
Should I measure for an inside mount or an outside mount?
Choose an inside mount when the frame is deep enough and you like the clean look. Choose an outside mount when the frame is shallow, uneven or when you want better light control around the edges.
Which width do I use if the three measurements differ?
For an inside mount, use the narrowest of the three widths, because the shade has to fit at the tightest point. Write down all three numbers so the installer can see them.
Do I need to subtract anything from my measurements?
Usually not. Give the exact numbers for the opening and let the maker apply the small allowance. Subtract only if the order instructions tell you to.
How accurate does the measurement need to be?
Measure to the nearest eighth of an inch and check each window twice. Custom shades are cut to your numbers, so small errors can mean a shade that does not fit.
Can Shade.Shop measure my windows for me?
Yes. Shade.Shop measures for free and quotes your project across Sonoma, Napa and Marin.
Get your windows measured for free
Shade.Shop serves homes across Sonoma and Napa. Contact us to schedule your free measuring visit and get a quote.
Planning a budget for your windows? See how much window shades cost by type.
