How to Measure for Recessed Blinds

How to measure for recessed blinds: start with the opening

A recessed blind sits inside the window opening, so the usable space matters more than the apparent size of the glass. First decide which window you are measuring and whether the blind will sit fully inside the recess. Clear the sill and move curtains or other coverings aside so their edges do not affect the reading. Keep a separate set of measurements for every window, even when two openings look identical.

Use a rigid tape measure marked in millimetres, a pencil and a note on your phone or paper. Measure from the finished surfaces that will remain after the blind is fitted, rather than from an unfinished edge that may change. Hold the tape straight across the opening and read it at eye level. Record each reading as you take it instead of relying on memory.

• Label the window and room before measuring.
• Record all dimensions in mm.
• Note whether the recess has a sill and where the blind may be fixed.

Measure the recess width in three places

Measure horizontally from the left inside edge of the recess to the right inside edge near the top. Repeat at the middle and near the bottom, keeping the tape level each time. Write down all three figures, even if they differ by only a few millimetres. The difference tells you whether the sides are parallel enough for a blind sized from a single reading.

Circle the smallest width as the limiting opening through which the blind must fit. Do not automatically subtract a clearance amount: some made-to-measure sellers ask for the exact recess width and make their own deductions. Others specify a finished blind size or ask you to apply an allowance. Check the product's measuring instructions and write down which convention its order form uses before entering a number.

Check the drop from top to sill or chosen endpoint

Measure vertically from the top inside surface of the recess to the sill on the left, in the centre and on the right. If there is no sill, identify the point where you want the blind to end and measure to that same level each time. Keep the tape vertical rather than following a sloping window frame. Record all three drops in millimetres and mark the shortest.

A short drop can reveal a sill that is not level or a top edge that varies across the opening. Check whether the chosen blind is intended to stop just above the sill or to extend to another endpoint. Follow the seller's instructions for ordering the drop; do not assume its width deduction rule also applies to height. If the blind must clear a handle or sill fitting, check that position with the blind lowered as well as raised.

Measure depth and identify obstructions

Depth is the distance from the front edge of the recess back towards the window. Measure it near the proposed bracket positions and compare the shallowest usable depth with the minimum stated for the chosen blind and its fittings. A deep opening does not help if a handle or vent projects into the path of the blind. Note the depth available before each obstruction, not just the full depth beside it.

Look for window handles, trickle vents, inward-opening sashes, tile returns and uneven plaster. Operate the window while considering where the headrail and fabric or slats will sit. A blind may physically fit within the recess but prevent the window from opening as intended. If that happens, consider a different blind, a different fixing position or an outside-recess fitting before ordering.

• Check usable depth at both proposed bracket locations.
• Record the position and projection of handles and vents.
• Confirm the window can still open.

Match the numbers to the blind and its fittings

Before ordering, identify the blind type and obtain its specific measuring and fitting instructions. Roller, Venetian and other blinds can have different headrails, brackets and side clearances. The width you enter may describe the recess, the complete blind including brackets, or the fabric alone. Treat those as different dimensions and check the wording beside the seller's size fields.

Check whether the brackets are intended for the top of the recess, its side walls or another suitable fixing surface. Examine the proposed fixing points for sound material and for anything that could interfere with a screw or bracket. If children could access the operating cord or chain, select and fit the supplied child-safety arrangement in accordance with the product instructions. Do not change its position or omit components simply to make a tight recess work.

Record the order dimensions and remeasure

Create one record per blind with the three widths, three drops, usable depth and any obstruction measurements. Add the product name, fitting position and whether the supplier requests exact recess dimensions or a finished size. This makes it possible to check the order later without reconstructing what an unlabeled number meant. Keep a photograph of the window with the intended fixing location marked if the opening is awkward.

Remeasure the smallest width and drop immediately before placing the order. Use the same finished edges and check that the tape is level or vertical as appropriate. If a reading changes, take all three measurements again rather than choosing whichever figure seems more convenient. Enter dimensions in the units shown on the order form, checking each digit and the width and drop labels separately.

Verification checklist

Use this final check after choosing the actual blind, since its fittings and order fields determine what the numbers mean. Compare the recorded opening with the supplier's stated minimum recess depth and measuring instructions. Where the instructions are unclear, ask the supplier to confirm which dimension it needs before submitting the order.

A complete record should let another person repeat your measurements at the same points. Keep the original readings alongside the number entered on the order form, particularly if an allowance was applied. Check the order confirmation against that record before the blind is made. This is especially useful for several similar windows where sizes are easy to transpose.

• Three widths and three drops are recorded in mm.
• The narrowest width, shortest drop and usable depth have been checked again.
• Handles, vents, opening sashes and fixing points have been checked.
• The order fields and any supplier-specified allowance are understood.
• The order confirmation matches the intended window and dimensions.

Scope and limitations

This note helps householders organise measurements and understand the calculation. It does not replace an on-site decision by a designer, installer, contractor, or manufacturer. Fabrication, structure, electrical work, gas, waterproofing, and personal safety require suitably qualified verification.