Blind Size Calculator
Enter your window measurements to the nearest 1/8 inch. The calculator picks the right numbers, checks your window depth, and tells you the size to order for an inside or outside mount.
Width (inside the frame, in inches)
Height (inside the frame, in inches)
Tip: measure with a steel tape, not a cloth one. Use decimals for fractions: 1/8 = .125, 1/4 = .25, 3/8 = .375, 1/2 = .5, 5/8 = .625, 3/4 = .75, 7/8 = .875.
Do not take deductions yourself on inside mount orders. The factory trims about 1/4 to 1/2 inch so the blind clears the frame. A free in-home measurement removes the guesswork entirely.
Have a Pro Measure for FreeHow to Use the Blind Size Calculator
Ordering the wrong size is the most common and most expensive mistake with custom blinds. This calculator takes your raw measurements and turns them into the size to order, using the same rules professional installers follow. Measure each window with a steel tape, enter the numbers, and choose your product and mount type.
Inside Mount Measuring Rules
For an inside mount, the blind sits within the window frame. Measure the width inside the frame at the top, middle, and bottom, and order the narrowest number. Then measure the height on the left, center, and right, and order the longest number. Do not subtract anything yourself. The factory trims the headrail slightly so the blind clears the frame without rubbing.
Depth decides whether an inside mount will work. Most two inch blinds need about one and a half inches of depth to mount, and a little over two inches to sit fully flush. Roller shades need less depth, while cassette valances need more. Enter your frame depth and the calculator will warn you if it is too shallow.
Outside Mount Measuring Rules
An outside mount covers the window frame and part of the wall. Measure the full area you want to cover, then add overlap on each side so light does not slip around the edges. One and a half inches per side is the minimum, and three inches gives better privacy and light control. Add room above the frame for the headrail or brackets. Outside mount is the right choice when the frame is shallow, out of square, or blocked by cranks and handles. Our guide to inside vs outside mount blinds explains the tradeoffs in more detail.
Common Measuring Mistakes
Measuring only once is the biggest mistake, since older windows are rarely square. Rounding to the nearest half inch is another, because a quarter inch can decide whether a blind fits. Measuring the old blind instead of the window, ignoring tile or trim that sticks into the opening, and forgetting window cranks also cause problems. When in doubt, have a pro measure. Our step by step guide on how to measure windows for blinds covers each step with examples.
Let a Pro Measure for Free
Every custom order we install starts with an in-person measurement, so you never pay for a blind that does not fit. Book a free in-home consultation and we will measure every window, check depth and square, and handle the full blind installation. Want a budget first? Try the blinds cost calculator or the plantation shutters cost calculator.