How to Measure for Roman Shades: Inside vs. Outside Mount

By Tina Bennett, Designer at UniCurt · Last updated July 2026 · ~7-min read

Here's the whole process, plus the one mistake that sends more Roman shades back than any other.

Step 1: Choose inside mount or outside mount

This decision changes how you measure, so make it first.

Choose an inside mount if:

• Your window has enough depth (our Roman shades need just 1.5 inches / ~4 cm of flat depth inside the frame).
• You want a clean, tailored look that shows off the window molding.
• Your window is reasonably square and free of obstructions (handles, cranks).

Choose an outside mount if:

• The window is shallow, out-of-square, or has a handle/crank in the way.
• You want maximum coverage and less light leakage at the edges.
• You want to make a small window look larger, or hide unattractive trim.

Step 2: Measure the width (3 points)

Using a steel tape, measure the width in three places — top, middle, and bottom of the window opening.

• Inside mount: record the narrowest of the three, to the nearest ⅛ inch, then subtract ¼ inch — we make the exact size you enter, so this small deduction is what lets the shade travel up and down freely. Windows are rarely perfectly square, which is why you use the narrowest number.
• Outside mount: decide how far past the opening you want to go — add roughly 1.5–2 inches (4–5 cm) on each side (3–4 inches total) to reduce side light gaps and give fuller coverage.

Step 3: Measure the height (3 points)

Measure top-to-sill in three places — left, center, and right.

• Inside mount: use the longest of the three, so the shade reaches the sill on every side.
• Outside mount: measure from where you'll mount the brackets (typically 2–4 inches / 5–10 cm above the frame, where you have flat surface) down to the sill — or a few inches below it for extra coverage.

Step 4: Check the depth (inside mount only)

For an inside mount, measure how deep the frame is from the front edge to the glass. UniCurt Roman shades need only 1.5 inches (about 4 cm) of flat depth to mount inside — shallower than the 2–3 inches many brands require, so more windows qualify. If you don't have it, go outside mount.

The #1 mistake: who takes the deduction?

This is the step that quietly ruins fit. When you measure a window opening for an inside mount, the shade has to be made slightly smaller than the opening so it can raise and lower without scraping. The question is who subtracts that gap — and it depends entirely on the maker:

• Some makers take the deduction for you, so you enter your exact opening size.
• Others — including us — make the exact size you enter. So for an inside mount, subtract about ¼ inch (0.6 cm) from your measured width yourself before ordering. For an outside mount, add your coverage and enter that number; we build it exactly as entered.

Whatever brand you buy from, confirm this one thing before you order — it's the difference between a shade that glides and one that's stuck or gappy. At UniCurt, we make the exact size you give us, so remember to deduct ¼ inch for an inside mount.

Comparison: inside vs. outside mount

A few things that trip people up

• Obstructions: a window handle or crank usually means outside mount.
• Out-of-square windows: outside mount hides the unevenness; inside mount will expose it.
• Protruding sills: account for a sill that sticks out — it affects where the shade lands.
• Cordless mechanisms: need a little more depth; check the spec if your shade is large.
• Multiple similar windows: order them all at the largest height so the pleats match across the room.

Easy to measure, easy to install — no installer needed

You don't need to hire anyone. Follow the three-point method above, remember the ¼-inch inside-mount deduction, and you're most of the way there. Installing is just as simple: our Roman shades come ready to mount with clear step-by-step tutorials, so most people put them up themselves in minutes with a screwdriver — no measuring appointment, no installer, no extra fees.

And because we make our Roman shades and curtains in the same original patterns and colorways, you can pair a shade with coordinating drapery from one collection — order a few high-quality swatches to see the fabric in your own light first. Every fabric is Oeko-Tex certified and backed by our 60-day satisfaction guarantee. Shop Roman shades

Frequently asked questions

How do you measure for Roman shades?
Choose inside or outside mount, then measure the width and height at three points each. For an inside mount, use the narrowest width and the longest height; for an outside mount, add coverage on the sides and top. Also check the window depth for an inside mount.

How much depth do you need for an inside-mount Roman shade?
UniCurt Roman shades need just 1.5 inches (about 4 cm) of flat depth inside the frame — less than many brands. If your window is shallower than that, choose an outside mount.

Should I subtract anything from my measurements?
Yes, at UniCurt. We make the exact size you enter, so for an inside mount, subtract about ¼ inch from your narrowest measured width so the shade can move freely. For an outside mount, add your coverage and enter that number. (Other makers deduct for you — always confirm before ordering.)

Inside mount vs outside mount — which is better?
Neither is universally better. Inside mount looks tailored and needs enough depth; outside mount covers more, blocks more light, and suits shallow, obstructed, or out-of-square windows.

How far should an outside-mount Roman shade extend past the window?
Roughly 1.5–2 inches on each side and 2–4 inches above the frame, so it covers the opening and reduces light gaps — more if you want to make the window look larger.