Measure bedroom window blinds by choosing inside or outside mount first, then using a steel tape to record the smallest width and largest height to the nearest 1/8 inch.
Decide whether you want an inside mount (blinds sit inside the frame) or outside mount (blinds cover the frame), then follow the steps below for your choice.
Inside Mount Measurements: Width, Height, and Depth
An inside mount fits snugly within the window frame and gives a clean, built-in look.
- Width: measure across the top, middle, and bottom of the frame; note the smallest number.
- Height: measure down the left, center, and right; note the largest number.
- Depth: measure from the front edge of the frame to the glass; compare this to the product’s minimum mounting depth before ordering.
Check for obstructions like window cranks, molding, or existing tracks that can block the blind’s hardware. If a crank protrudes into the frame, an inside mount often won’t work — switch to an outside mount instead.
Outside Mount Measurements: Coverage and Overlap
An outside mount covers the entire frame and extends past it, giving you maximum light control and privacy — often the better pick for bedrooms. Measure the exact area you want covered, then add overlap so the blind blocks light around the edges.
Extend the height above the frame as needed to clear the hardware. If your window frame isn’t square, an outside mount hides that and provides better coverage.
Recording Your Numbers and Avoiding Measuring Mistakes
Write each window’s measurements as width x height (W x H) and measure every window individually — two windows in the same room can differ by more than you’d expect. Use a steel or metal tape measure that reads to the nearest 1/8 inch and avoid cloth tapes, which stretch and give you inaccurate numbers.
The most common mistakes people make: measuring only once instead of three times in different spots, rounding to the nearest half inch or whole inch instead of 1/8 inch, and mixing up the width and height order. For bedrooms where light control matters, double-checking these three details makes the difference between blackout and a bright morning.
Once you have your exact numbers, compare the best bedroom window blind options to find a style that fits your measurements and light-control needs.
| Measurement | Inside Mount | Outside Mount |
|---|---|---|
| Width | Smallest of 3 measurements (top, middle, bottom) | Coverage area plus overlap (about 3/4 inch per side) |
| Height | Largest of 3 measurements (left, center, right) | Coverage area plus overlap (about 3 inches total) |
| Depth | Must exceed product’s minimum mounting depth | Not needed; hardware mounts outside the frame |
| Precision | Nearest 1/8 inch | Nearest 1/8 inch |
| Record format | W x H (width before height) | W x H (width before height) |
| Best for | Square frames with no obstructions | Non-square windows, cranks, maximum privacy |
The biggest pitfall is assuming your main bedroom window matches the guest room window next to it.
One more inside-mount warning: measure the depth even if the width and height look perfect. A shallow frame that lacks clearance for the mounting brackets and track will force the blind to stick out or bind. If your frame depth comes up short, Home Depot’s blinds and shades measuring guide confirms an outside mount is the reliable fallback when the opening simply won’t accommodate the hardware.
Double-Check the Diagonals for Square Frames
Before you order inside-mount blinds, measure the frame diagonally from corner to corner in both directions.
FAQs
What tape measure is best for measuring window blinds?
A steel or metal tape measure gives accurate, non-stretching readings to the nearest 1/8 inch.
Should I round my blind measurements up or down?
For inside mounts, record the exact smallest width to the nearest 1/8 inch. For outside mounts, round up slightly after adding overlap so the blind fully covers the frame and blocks light around the edges.
How much overlap should an outside-mount blind have?
This extra overlap blocks light from leaking around the frame and gives you more privacy in the bedroom.
References & Sources
- Home Depot. “How to Measure for Blinds and Shades.” Details the three-point measuring method and outside-mount overlap guidance.
