Determine the correct measurements for your window blinds based on mount type and window size to ensure a perfect fit.
Last updated: March 2026
Important Note: This calculator provides a rough starting point based on standard industry assumptions. In reality, blind sizing varies significantly by manufacturer, product type (roller, cellular, vertical, etc.), material, and mounting hardware. Inside-mount deductions range from 0.25" to 1", and outside-mount overlaps depend on your specific design goals. Always confirm final measurements with your blind manufacturer or retailer before ordering. Most quality blind suppliers offer free measuring guides and customer service consultations to ensure proper fit.
Window blinds are adjustable window coverings hung from the top of a window frame or wall. They consist of horizontal or vertical slats that can be opened, closed, or adjusted to control light and privacy. Blinds are available in various materials including wood, plastic, aluminum, and fabrics, each offering different aesthetics and functionality.
The key to successful blind installation is accurate measurement and choosing the correct mount type. Inside mount blinds (installed within the window frame) provide a clean, integrated look, while outside mount blinds (mounted to the wall or trim) cover more window area and allow for better light control and privacy. However, sizing conventions differ significantly across manufacturers. This calculator provides a starting estimate based on typical industry assumptions—it is not a substitute for manufacturer-specific measuring guides.
For inside mount, measure the window opening from inside the frame:
For outside mount, measure wall or trim area where blinds will mount:
Window opening measures 36" wide × 48" tall for inside mount installation:
This deduction prevents the blind from rubbing against the sides of the window frame and jamb. It allows smooth operation without binding or damage.
Standard minimum is 2 inches on each side. For better light control and privacy, increase to 3-4 inches. More overlap creates a more finished, professional appearance.
This is normal. Always measure in at least three places. For inside mount, use the smallest width and largest height. For outside mount, measure the desired coverage area.
Minimum 2 inches for most blind hardware. Check manufacturer specifications for your chosen blind type, as some require additional clearance.
Yes, but you'll need outside mount. Inside mount won't work because of the angle. Measure carefully and consider custom installation for best results.
Simple inside mount blinds are DIY-friendly. Outside mount and complex installations benefit from professional help to ensure proper alignment and function.
Most blind manufacturers offer custom sizing. Provide your exact measurements (even unusual dimensions), and they'll produce blinds to fit precisely.
When blinds arrive, test fit them before installation. Inside mount should slide smoothly into the frame. Outside mount should align properly on the wall/trim.
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