How to Measure Your Windows for Custom Blinds (Before We Even Show Up)

Every quote we send out is based on a final, on-site measure — that part doesn't change, because a rough estimate off a tape measure at home and a millimetre-precise measure with our tools are two different numbers, and only one of them is safe to manufacture from. But knowing roughly what you're working with before we visit still helps: it lets you budget more accurately, compare mount options intelligently, and ask sharper questions during your consultation instead of guessing.

This guide walks through how to get a good working number for your own planning, and why we still remeasure everything ourselves before anything goes into production.

Inside mount vs. outside mount, decided first

Before you measure anything, decide whether you want an inside mount (the blind sits inside the window frame, flush with the wall) or an outside mount (the blind mounts on the wall or trim above and around the window, covering the frame entirely). This decision changes what you're measuring, so it has to come first.

Inside mounts look cleaner and let trim and casing show, but they need at least 2–3 inches of depth in the frame for most products, and they expose any wonkiness in the window opening itself. Outside mounts are more forgiving of an uneven frame, offer better light-blocking and privacy since the blind can extend past the opening, and are usually the right call for windows with limited depth or a frame that isn't square.

Measuring for an inside mount

Measure the width at the top, middle, and bottom of the inside of the frame, and use the smallest of the three numbers — frames are rarely perfectly square, and undersizing slightly is safer than overestimating. Do the same for height: measure at the left, centre, and right of the opening, and note the smallest measurement.

Also check the depth of the frame at a few points along its face — this tells you (and us) whether there's room for the product you're picturing, or whether it needs to move to an outside mount instead.

Measuring for an outside mount

For an outside mount, you're measuring how far past the window opening you want the blind to extend, not the opening itself. A common approach is to add 2–4 inches of overlap on each side and 2–3 inches above the top of the frame, more if you want maximum light-blocking or privacy (for example, in a bedroom).

Outside mount height should also account for anything below the window — a countertop, radiator, or sill — so the blind has clear room to sit without interference when lowered.

Why we still remeasure everything ourselves

Custom blinds are manufactured to the millimetre, and a few millimetres of error is the difference between a blind that hangs flush and one with visible gaps at the edges. Frames also aren't always square — a window can be a few millimetres wider at the top than the bottom, which a rough home measurement won't catch but our laser tools will.

Bring your rough numbers to your consultation if you'd like — they're genuinely useful for budgeting and narrowing down mount type and product — but every order we manufacture is built from our own on-site measurement, taken the same visit we discuss your options.