How to Measure Windows for Blinds: A Step-by-Step Guide

To measure a window for blinds, first decide whether the blind will sit inside the window recess or outside it on the wall. For an inside mount, measure the recess width at the top, middle and bottom and use the smallest figure; measure the height at the left, centre and right and use the largest. For an outside mount, measure the area you want to cover and add about 3 to 4 inches on each side and above the window.

That is the short version. Below is the full method, the tools you need, and the small mistakes that cause most blinds to fit badly.

What you need

• A steel measuring tape — cloth tapes stretch and give wrong readings.
• A pencil and paper, or your phone's notes app.
• A step stool for tall windows.
• About ten minutes per window. Measure every window separately, even if they look identical — in Indian homes, "identical" windows often differ by half an inch or more.

Step 1: Decide on inside or outside mount

Inside mount places the blind within the window recess. It looks neat and built-in, and leaves the wall and sill clear. It needs a recess deep enough to hold the bracket — usually about 2 to 3 inches for a roller blind, more for wooden slatted blinds — and it leaves thin light gaps at the sides.

Outside mount fixes the blind on the wall or ceiling above the window and lets it overlap the opening. It blocks more light, hides uneven or shallow recesses, and can make a small window look larger. It is the better choice for bedrooms that need darkness, and for windows with handles or grilles that stick out.

Step 2: Measuring for an inside mount

1. Width: measure the inside of the recess at the top, middle and bottom. Write down the smallest of the three. Walls are rarely perfectly straight, and the blind must fit the narrowest point.
2. Height: measure from the top of the recess to the sill at the left, centre and right. Write down the largest.
3. Depth: measure how deep the recess is, and check for anything that would block the blind — window handles, tower bolts, grilles or sliding tracks.
4. Don't deduct anything yourself. Give the exact recess size; the manufacturer makes the small allowance needed for the brackets and fabric to clear the sides.

Step 3: Measuring for an outside mount

1. Width: measure the width of the opening (or the frame), then add 3 to 4 inches on each side. This overlap is what stops light leaking around the edges.
2. Height: measure from where the bracket will sit — usually 3 to 4 inches above the opening — down to where you want the blind to end, typically a few inches below the sill or to the sill itself.
3. Check clearance: make sure the bracket position is clear of the curtain track, AC unit, switchboards or the false ceiling edge.

Special cases

• Windows with grilles: if the grille is inside the frame, an inside-mounted blind may not have room to drop. Measure the depth between the glass and the grille, or plan an outside mount.
• Sliding windows and doors: make sure the blind clears the handles when the panel slides. For wide sliding doors, a vertical blind or two blinds side by side often works better than one very wide blind.
• Very wide windows: fabric blinds have practical width limits. If a window is wider than about 8 to 10 feet, you may need two or three blinds sharing a headrail.
• Bay and corner windows: measure each section separately and note where the blinds meet, so they don't clash at the corners.

Turn your measurements into an estimate

Blinds are priced by area, so convert your size into square feet: width (ft) × height (ft) = sq ft. Convert inches to feet by dividing by 12, and round up.

Example: a window 52 inches wide and 62 inches tall is about 4.33 × 5.17 ft, or roughly 22.4 sq ft — call it 23 sq ft. At our rate of ₹130 to ₹350 per sq ft including installation, that is about ₹2,990 to ₹8,050, depending on the type of blind. See our guide to the types of window blinds to understand where each type falls in that range.

Common measuring mistakes

• Using one width measurement instead of three, so the blind jams at the narrowest point.
• Forgetting window handles, which stop an inside-mounted blind from dropping.
• Measuring the glass instead of the recess or the opening.
• Mixing up width and height — always write width first.
• Rounding down. Always round up when estimating cost; never adjust sizes yourself when ordering.

Should you measure yourself?

Measuring yourself is useful for planning a budget. For the final order, a professional measurement is worth having: the installer checks the wall material, recess depth and obstructions, and takes responsibility for the fit. Our site visits across Delhi NCR are free.

Akhil Interior measures, makes and installs blinds across Delhi NCR and delivers pan-India. See the full window blinds range or book a free consultation and we'll recommend the right fabric and mechanism for each room.

Frequently asked questions

How much should a blind overlap the window?

For an outside mount, add about 3 to 4 inches on each side and above the opening. For bedrooms where you want maximum darkness, a slightly larger overlap helps even more.

Should I measure the window glass or the frame?

Neither, exactly. For an inside mount, measure the recess (the opening in the wall). For an outside mount, measure the area of wall you want the blind to cover, including the overlap.

How deep should a recess be for an inside-mounted blind?

Most roller blinds need about 2 to 3 inches of depth to fit fully inside; slatted wooden blinds need more. If the recess is too shallow, use an outside mount.

Do I deduct anything from the width for an inside mount?

No. Give the exact narrowest recess width and mention that it is an inside mount. The maker deducts the small clearance needed so the blind runs freely.