Sunday, July 26, 2026 — Wholesale Blind Factory
Measuring for blinds comes down to one decision made before you pick up a tape measure: will the blind sit inside the window frame or outside, covering the frame and wall around it? For an inside mount, you measure the narrowest width and the longest height of the opening itself. For an outside mount, you measure the area you want covered and add overlap on every side so light and gaps are blocked. Get this step wrong and the blind either won't fit or won't do its job.
An inside mount fits inside the window recess, flush with the frame, for a clean, built-in look. It only works if the frame has enough depth to hold the headrail and enough square, even sides for the blind to hang straight. An outside mount attaches to the wall or trim above and around the window, covering the frame entirely. It's the go-to choice when a frame is too shallow, uneven, or when you want the window to look larger, need better light blockage, or you're covering a patio door or window with no recess to mount into.
Both mount types are available across our venetian blinds, cellular shades, and roller shade lines, so the decision usually comes down to your frame's depth and the look you want, not the product itself.
Inside mount measurements are taken from inside the window frame, at three points, so the blind fits even if the frame isn't perfectly square (most older BC homes aren't).
If the frame depth is too shallow, or the sides taper noticeably, an inside mount may not sit flush or could bind when raised. That's the point to switch to outside mount instead.
Outside mount measurements cover the area you want hidden, not the window opening itself, so there's deliberate overlap built in.
As a rule of thumb: choose inside mount for a clean, tailored look when your frame has enough depth and is reasonably square. Choose outside mount when the frame is too shallow, uneven, or you want maximum light blockage — a common choice for bedrooms wanting near-total blackout, or for windows without a proper recess like patio doors. Outside mount also makes a small window appear larger, since the blind extends beyond the actual glass.
A steel tape measure is more accurate than cloth or laser measures for this job, since window openings rarely have a perfectly flat surface to bounce a laser off. Measure to the nearest 1/8 inch (or nearest millimetre if you're working metric), and always record three measurements per dimension rather than one — most window frames settle unevenly over the years, and a single measurement can be off by enough to cause a fitting problem.
If you'd rather not risk a mismeasure on a custom order, our team offers a free in-home consultation where we measure every window, confirm the right mount type for your frame, and provide a firm quote on the spot. It's the easiest way to make sure a made-to-order blind fits the first time. Call (604) 942-4201 or book online, or browse ready-to-order options at /shop once you know your measurements.
Usually not without buying a new blind, since the headrail and slat or shade width are built to the original measurements. If you're unsure which mount suits your window, it's worth confirming frame depth before ordering rather than after.
If the frame is less than about 2 inches deep, an inside mount likely won't clear the glass, handle, or crank. An outside mount is the safer choice in that case, and it also gives better light blockage since it covers the frame edges.
The width and height measurement process is the same for motorized and manual blinds. The main difference is depth — motorized headrails can be slightly bulkier, so confirm clearance if you're mounting inside a shallow frame.
Yes. Even windows that look identical often differ by a few millimetres due to settling or the original build, especially in older Vancouver-area homes. Measure and record each window individually rather than reusing one set of numbers.