Your Guide to Measuring Blinds Correctly at Home
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A blind that is a few millimetres too wide will not sit in the recess. One that is too narrow can leave awkward gaps, reduce privacy and let in more light than you expected. This guide to measuring blinds correctly keeps the job simple, whether you are ordering a new roller blind, replacing vertical slats or updating a whole room.
You do not need specialist tools or an in-home appointment. A reliable steel tape measure, a pencil and a few careful checks are usually enough. Measure every window separately, even if they look identical. Window recesses, tiles, handles and frames often vary more than you can see at a glance.
Before You Measure Your Windows
Start by deciding where the blind will be fitted. This is the one decision that affects every measurement that follows.
A recess fit means the blind sits inside the window recess, between the walls or frame. It gives a neat, built-in look and is often a good choice where there is enough depth for the blind and its brackets. Recess fitting can work well for roller blinds, vertical blinds and blackout blinds, but only if there are no handles, vents or glazing strips in the way.
An exact fit, sometimes called outside-recess fitting, means the blind is fitted on the wall, window frame or ceiling outside the recess. This is useful for shallow recesses, windows with obstructions, or when you want more light coverage. For bedrooms, an outside-recess blackout blind can help reduce light around the edges, although no standard blind is guaranteed to create total darkness without considering the side gaps and installation position.
Check the product measuring instructions before placing an order. Different blind types can have different brackets, headrails and fabric widths. The width of a roller blind's fabric, for example, is usually narrower than the overall bracket-to-bracket width.
Use a Steel Tape Measure
A steel tape measure is the best choice. Fabric tapes can stretch or bend, and rulers are too short for accurate full-width measurements. Measure in millimetres rather than centimetres. It avoids decimals and gives the clearest size for a made-to-measure order.
Write each measurement down as soon as you take it. Label it by room and window, such as “kitchen sink window” or “main bedroom left”. If you are measuring several similar windows, this small bit of organisation prevents expensive mix-ups later.
How to Measure Blinds for a Recess Fit
For a recess fit, measure the inside of the opening, not the glass and not the existing blind. Take three measurements for the width: at the top, middle and bottom of the recess. Then take three drops: on the left, in the centre and on the right.
Use the smallest width and the smallest drop. Recesses are not always perfectly square, particularly in older homes, and using the smallest measurements gives the blind the best chance of fitting cleanly.
Do not make your own width deductions unless the product instructions specifically tell you to. Made-to-measure suppliers often apply an allowance for recess-fitted blinds so the mechanism has working clearance. If you deduct a few millimetres yourself and the supplier does the same, the finished blind may be unnecessarily narrow.
Measure the recess depth too. You may not need to enter it when ordering, but it tells you whether the brackets and blind can sit inside the opening. Look out for inward-opening windows, large handles, alarm sensors, trickle vents and tiles. A blind that technically fits the recess may still catch when you open the window.
For a roller blind, check which side you want the control chain on. Choose the side that is easiest to reach and least likely to interfere with a handle. Keep chains safely secured using the supplied safety device, especially in homes with young children.
Recess Fit Example
If your width measurements are 1,205mm at the top, 1,202mm in the middle and 1,204mm at the bottom, order or submit 1,202mm as the recess width, following the retailer's measurement guidance. If your shortest drop is 1,480mm, use 1,480mm for the recess drop.
That is all there is to it: smallest width, smallest drop, no guesswork.
How to Measure Blinds for an Exact Fit
An exact fit gives you control over how much of the wall or frame the blind covers. Rather than measuring the recess itself, decide the finished blind size you want.
First, measure the width of the area you need to cover. If fitting above a recess, add overlap on both sides. Around 50mm each side is a common starting point, but more may be better if space allows and privacy or light reduction is the priority. Check for nearby light switches, shelves, cupboards and curtain poles before choosing a wider blind.
For the drop, measure from the point where the brackets will be fitted to where you want the blind to finish. A wall-mounted blind may finish below the window sill for better coverage. A blind fitted to the ceiling may need extra drop to reach the same point.
When you submit an exact-fit measurement, it is normally the finished overall blind size you want. Do not rely on the glass measurement alone. The brackets, headrail and fabric need room beyond the glass to do their job.
Exact fitting is often the practical choice in bathrooms and kitchens where tiles, shallow recesses or window openings make an inside fit difficult. PVC waterproof blinds are particularly useful in steamy or splash-prone spaces because they are simple to wipe clean. Just make sure the blind is positioned clear of taps, extractor controls and cupboard doors.
Measuring Vertical Blinds and Replacement Slats
Vertical blinds need a little extra care because the headrail and slats are separate parts. For a complete vertical blind, use the same recess or exact-fit method above, then confirm the finished width and drop required for the headrail and slats.
If you are replacing vertical slats rather than the full blind, measure one existing slat from the very top, including the hanger hole or slot area, to the bottom. Do not measure only the visible fabric below the headrail. Measure two or three slats if possible, particularly if the current blind has been trimmed or has uneven ends.
Also check the slat width. Common sizes exist, but guessing is not worth it. Measure the slat across its face and check the top hanger style before ordering replacements. This is a cost-effective way to refresh a rental property, replace sun-faded fabric or change the look of a room without buying a new headrail.
If the old slats are missing, measure from the underside of the headrail to the point where the slats should end. Take the measurement in several places if the floor or sill is uneven, then use the shortest practical drop so the slats do not drag.
Common Measuring Mistakes to Avoid
Most fitting problems come from a rushed first measurement, not from the blind itself. Avoid these common errors:
- Measuring just once. Always take three widths and three drops for a recess.
- Measuring the glass instead of the recess or intended coverage area.
- Giving centimetres when the order form asks for millimetres.
- Making deductions for a recess fit without checking the product instructions.
- Forgetting handles, vents, tiles, radiators or inward-opening windows.
- Assuming two windows are the same size because they look alike.
- Ordering replacement vertical slats by visible length rather than full slat length.
A Final Check Before Ordering
Read your measurements back against your notes. Confirm the room, fitting type, width, drop, control side and any clearance issues. If you have chosen a patterned roller blind, consider whether the pattern position matters at the bottom edge. If blackout is your priority, think about coverage rather than fabric alone.
At Queen Blinds, made-to-measure options are designed to take the hassle out of finding an off-the-shelf size that is almost right. A few careful minutes with a tape measure gives you a blind that looks neater, works properly and earns its place in the room for years to come.