Blinds and shades are usually made to measure, and a wrong number by half an inch can mean a blind that does not fit inside the frame. This calculator turns your measurements into the size to order for both mount types.
Inside or outside mount?
- Inside mount: the blind sits inside the window opening. It looks clean and shows off the trim, but it needs enough depth (often 1 to 2 in for a blind, more for a flush fit) and lets thin strips of light pass at the sides.
- Outside mount: the blind is fixed on the wall or trim above the window. It hides out-of-square frames, blocks more light and makes the window look bigger.
How to measure
Use a steel tape measure, not a cloth one, and write down to the nearest 1/8 in.
- Measure the width at the top, middle and bottom of the opening.
- Measure the height at the left, middle and right.
Windows are rarely perfectly square, so the three values differ.
Inside mount
- Width: take the narrowest of the three. Most makers then take a small deduction (about 1/4 in) at the factory so the blind operates without rubbing; if yours does not, enter that clearance in the calculator.
- Height: take the tallest so the blind reaches the sill everywhere.
Do not deduct anything yourself unless the maker asks you to: a double deduction leaves wide light gaps.
Outside mount
- Width: take the widest measurement and add an overlap on each side, typically 1.5 to 3 in, to block light and hide the frame.
- Height: add room above the frame for the brackets and headrail, typically 3 in, and an overlap below the sill if there is one.
Example
Widths of 35 1/2, 35 1/4 and 35 3/8 in and heights of 60, 60 1/4 and 59 7/8 in give an inside-mount order of 35 1/4 × 60 1/4 in, about 14.7 sq ft. For an outside mount with 1.5 in on each side, 3 in above and 1.5 in below, the order becomes 38 1/2 × 64 3/4 in.
Price
Blinds are often priced by size bands rather than by area. The price per square foot here gives a rough budget: cheap vinyl and roller shades start low, while wood, cellular and motorized shades cost several times more.