How to measure for custom blinds (inside vs outside mount)

Measuring for custom blinds is straightforward — but the rounding rules and the inside-vs-outside mount choice trip up most first-time buyers. Five minutes of careful measurement saves you a $300 remake.

What you need

• A steel tape measure (not a soft fabric one)
• A pencil and a piece of paper
• A step stool if your window is tall

Inside mount: measure the opening

An inside-mount blind sits inside the window frame. This is the cleaner look — the blind is recessed into the window itself, the trim stays visible around the edges.

Width: measure the inside width of the window opening at three points — top, middle, bottom. Record the narrowest measurement. Round to the nearest 1/8 inch.

Height: measure the inside height at three points — left, middle, right. Record the longest measurement (so the blind reaches the sill). Round to the nearest 1/8 inch.

Depth: measure how deep the window is from the front trim to the glass. You need at least 2 inches of clearance for most blinds, 3.5 inches for plantation shutters. If your depth is less, switch to outside-mount.

Outside mount: measure including trim

Outside-mount blinds cover the window opening and the trim around it. This is the blockout-friendly choice — fewer light gaps, more privacy.

Width: measure the full width you want the blind to cover. Add 1.5 inches of overlap on each side of the window for proper blockout. So a 30-inch window opening becomes a 33-inch blind.

Height: measure from where you want the top of the blind to where you want the bottom. Most homeowners go 2-3 inches above the window frame and to the sill (or a few inches below).

When to pick which mount

Choose inside-mount if	Choose outside-mount if
You have at least 2" of depth	The window is shallow (under 2")
You want the trim to show	You want to hide the trim
You want a cleaner look	You want maximum blockout
The window is square and true	The window is irregular or out-of-square

Common mistakes

Rounding the wrong way. Inside-mount: always use the narrowest width and longest height. Outside-mount: use the actual desired dimensions plus overlap. Never round up on inside-mount width — the blind won't fit.

Forgetting depth. If your window is shallow and you order inside-mount, the blind sticks out into the room. Measure depth before you order.

Not measuring at three points. Old houses settle. A window that looks square is often 1/4 inch narrower at the bottom than the top. Three measurements, take the narrowest for width.

What to do next

Once you have width × height in inches: open the configurator and enter the numbers. Pick your color, mount type, and motorization. See a photoreal preview in your room.