Roller shades look clean and simple, but a shade that's a fraction of an inch off can leave light gaps, rub the frame, or refuse to fit at all. The good news: measuring for roller shades is quick once you know the two things that matter most, your mount type and three careful measurements. This step-by-step guide walks you through both, so your custom shades fit right the first time.
Quick answer: First decide on an inside mount (shade sits inside the window recess) or an outside mount (shade mounts on the wall/frame above the window). Then measure the width in three places (top, middle, bottom) and the height in three places (left, center, right) with a steel tape. For an inside mount, record the measurements exactly, don't subtract anything; the factory makes the small clearance deduction. For an outside mount, add 2–3" on each side and 3–4" above the opening for the best light coverage.
Before You Start: Inside Mount or Outside Mount?
Everything about measuring depends on this one choice, so make it first. An inside mount sits neatly inside the window opening for a clean, built-in look, but it needs enough flat depth for the roller tube. An outside mount attaches to the wall or trim above the window, covers more glass, and is the fix when your recess is too shallow or out of square.
| Inside mount | Outside mount | |
|---|---|---|
| Look | Built-in, flush, minimal | Bigger, covers the frame |
| Light gaps | Small gaps at the sides | Best light blocking (overlaps) |
| Needs | Enough recess depth for the tube | Flat wall/trim above the window |
| Best for | Deep, square windows; a clean look | Shallow/uneven recesses; max darkness |
Tip: for a bedroom or nursery where full darkness matters, an outside mount (or an inside mount paired with side channels) leaks the least light. See our blackout roller shades guide for room-darkening tips.
What You'll Need
- A steel tape measure (never cloth, it stretches)
- A pencil and paper (or your phone) to record each number
- A step stool for tall windows
- A level, if you're checking an outside-mount location
Always measure the actual window, not an existing shade or blind, and measure every window separately even if they look identical, openings often vary by a fraction of an inch.
How to Measure for an Inside Mount
An inside-mount roller shade fits within the window opening, so precision matters most here.
- Measure the width in three places — across the top, middle, and bottom of the opening, inside edge to inside edge. Windows are rarely perfectly square.
- Measure the height in three places — on the left, center, and right, from the top of the opening down to the sill.
- Record all six numbers to the nearest 1/8". For custom made-to-order shades, send these exact opening measurements and simply note "inside mount", the factory applies the correct deduction so the shade clears the frame and rolls smoothly.
- Check the depth. Measure how deep the recess is (front of window to the wall). Most roller shades need a small amount of flat depth for the tube and brackets; if it's shallow, choose an outside mount instead.
Which numbers do you use? If you were sizing a ready-made shade yourself, you'd take the narrowest width and the longest height. With Curtarra's made-to-measure shades you don't have to do that math, send the exact opening sizes and mark it inside mount; we handle the fit.
How to Measure for an Outside Mount
An outside-mount shade covers the opening plus some surrounding wall, so you're measuring the finished size you want the shade to be, not the opening.
- Width: measure the opening width, then add 2–3" on each side (4–6" total) so the shade overlaps the frame and blocks side light.
- Height: measure from where you'll mount the bracket (usually 3–4" above the opening) down to where you want the shade to end, at or just below the sill.
- Check the mounting surface. Make sure there's enough flat wall or trim above the window for the brackets, and that it's a solid surface to screw into.
- Send the finished size. For custom outside-mount shades, the measurements you provide are the shade's overall size, no deduction is made.
Common Roller Shade Measuring Mistakes
| Mistake | Why it's a problem | Do this instead |
|---|---|---|
| Measuring once | Windows aren't square; a single number misses gaps or binding | Measure width and height in 3 spots each |
| Using a cloth tape | It stretches and reads long | Use a steel tape |
| Deducting yourself on custom | Double deduction = a shade that's too small | Send exact opening + note "inside mount" |
| Ignoring recess depth | The tube won't fit or protrudes | Measure depth; go outside mount if shallow |
| Rounding to the nearest inch | Loses up to ~1" of fit | Record to the nearest 1/8" |
Ready to Order Your Custom Roller Shades
Once you have your measurements, choosing is the easy part, pick the fabric for the room's job and place your order to your exact size. Popular made-to-measure picks: the 100% blackout Derick for bedrooms, the Lillian light-filtering shade for living rooms, and the Leo solar shade for sunny rooms with a view. New to roller shades? Start with what are roller shades to pick your fabric and lift.
Frequently Asked Questions
How do I measure a window for roller shades?
Decide on inside or outside mount first. Then use a steel tape to measure the width in three places (top, middle, bottom) and the height in three places (left, center, right). For an inside mount, record the exact opening and note "inside mount", the factory makes the deduction. For an outside mount, add 2–3" on each side and 3–4" above the opening.
Should I measure width or height first?
Always list width first, then height (W x H) — it's the industry standard, and reversing them is a common ordering error. Measure both in three places and record each number to the nearest 1/8".
Do I subtract anything for an inside-mount roller shade?
Not for custom made-to-order shades. Send the exact window opening measurements and mark it as an inside mount; the manufacturer applies the correct clearance deduction so the shade fits and rolls freely. Only subtract yourself if a ready-made product's instructions tell you to.
How much overlap should an outside-mount roller shade have?
Add about 2–3 inches on each side (4–6 inches total width) and mount the bracket 3–4 inches above the opening. More overlap covers more glass and blocks more side light, which is ideal for bedrooms.
How much recess depth do roller shades need?
Roller shades need a modest amount of flat depth inside the window for the tube and brackets. If your recess is shallow or obstructed by handles or cranks, choose an outside mount so the shade sits proud of the opening.
What if my window isn't square?
Very common. That's exactly why you measure in three places. For an inside mount you send the exact opening (we handle the fit); if the opening is badly out of square, an outside mount hides the unevenness and gives a cleaner look.
Keep Reading
Measured and ready? Curtarra roller shades are made to your exact window in blackout, light-filtering, and solar fabrics, cordless or motorized. Order free color-card samples to choose your fabric with confidence.
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