Blind Size
Calculate exact window blind dimensions for inside or outside mount. Enter width and height measurements to get precise blind size recommendations instantly.
Width Measurements (inches)
Height Measurements (inches)
About This Calculator
The Blind Size Calculator helps homeowners, DIY enthusiasts, and interior decorators determine the exact window blind dimensions needed for any window. Whether you are replacing old blinds or installing new ones, getting the correct measurements is essential for a proper fit and professional look.
Window blinds come in two mounting styles. Inside mount blinds sit within the window frame for a sleek, built-in appearance. Outside mount blinds extend beyond the frame and are better for blocking light, covering uneven windows, or making a window look larger. Each style requires a different calculation method.
How the Blind Size Calculation Works
For inside mount blinds, the calculator takes the smallest of the three width measurements (top, middle, bottom) to ensure the blind fits inside the frame without binding. For height, it uses the longest measurement and subtracts 1/4 inch for clearance so the blind does not drag on the sill.
For outside mount blinds, the calculator takes the largest width measurement and adds 3 inches total (1.5 inches per side) for proper overlap. For height, it adds 1.5 inches to the longest measurement to cover the top of the window frame.
Why Accurate Measurements Matter
Measuring a window for blinds requires precision. Windows are rarely perfectly square, which is why taking width measurements at three points and height measurements at three points is recommended. A difference of even 1/4 inch between the top and bottom width can affect how the blind fits. Using the smallest width for inside mounts prevents binding, while using the largest width for outside mounts ensures full coverage.
Standard blind sizes are available for common window types including picture windows, sliders, and double hung windows. For non-standard window sizes, custom blinds or cut-to-size options are widely available from home improvement stores and online retailers.
Frequently Asked Questions
How do I measure my window for blinds?
Measure the width of your window at the top, middle, and bottom from inside the window frame. Then measure the height at the left, center, and right. Record all six measurements in inches for the most accurate blind sizing results.
What is the difference between inside mount and outside mount blinds?
Inside mount blinds sit inside the window frame for a clean built-in look. Outside mount blinds extend over the window frame and are ideal for uneven windows, better light blocking, or making windows appear larger. Inside mounts use the smallest width while outside mounts add overlap to the largest width.
What size blind do I need for a 34.5 inch wide window?
For an inside mount, the blind width should be the smallest of your top, middle, and bottom width measurements — typically the actual window width minus a small clearance. For an outside mount at 34.5 inches, add 3 inches for a total blind width of 37.5 inches to ensure proper overlap on both sides.
Should I subtract anything from the measurements for inside mount blinds?
Yes, for inside mount blinds, subtract 1/4 inch from the longest height measurement so the blind does not drag against the window sill. The width uses the smallest measurement without subtraction to ensure the blind fits inside the frame without binding.
How much overlap do I need for outside mount blinds?
For outside mount blinds, add 3 inches to the widest width measurement (1.5 inches overlap on each side) and add 1.5 inches to the tallest height measurement for top overlap. This ensures the blind fully covers the window opening and blocks light effectively.
What are standard window blind sizes?
Standard blind sizes vary by window type. Picture windows range from 12 to 96 inches in height and 24 to 96 inches in width. Sliders are 24 to 60 inches tall and 36 to 84 inches wide. Double hung windows measure 36 to 72 inches in height and 36 to 84 inches in width. Many stores cut blinds to size for custom fit.
Can I cut blinds to size if they are too wide?
Yes, many blinds can be cut to size, especially faux wood and aluminum blinds. However, cutting blinds requires the right tools and careful measurement. It is often easier to order custom size blinds from retailers who cut them to your exact specifications for a precise fit.
Is the Blind Size Calculator free to use?
Yes, all calculators on Calculy are completely free to use. The Blind Size Calculator provides instant recommendations for both inside and outside mount blinds with no registration or payment required.