Measuring for Blinds and Curtains: Recess and Exact Fit
How to measure windows for blinds and curtains in UK homes, including recess and exact fit, drops, widths, depth checks and common errors.
A blind that is 1 cm too wide will not fit, and curtains that stop short of the sill look unfinished. Measurement mistakes are the most common reason for returns and awkward fittings. A tape, a pencil and a little patience will save you money and time.
Recess or exterior fit?
Before measuring, decide how the blind will sit.
- Recess (inside) fit: the blind sits inside the window reveal. It looks neat and uses less fabric, but needs enough depth and a reasonably square opening.
- Exact fit or exterior fit: the blind hangs on the wall or window frame, covering the opening and some surrounding surface. It blocks more light and hides uneven edges.
Check the depth of the recess: many blinds need a minimum depth to fit. Windows with handles that stick out may prevent a blind from sitting flush.
Tools you need
- A steel tape measure, which does not stretch.
- A pencil and notepad.
- A ladder or stool for taller windows.
- A spirit level, to see if edges are square.
Measuring for a recess blind
- Measure the width at the top, middle and bottom of the recess.
- Use the narrowest of the three measurements.
- Measure the drop on the left, centre and right, and note the longest if you want it to touch the sill, or the shortest if you want a gap.
- Check the depth for handles, catches and cills.
- Write down numbers in millimetres, and note the order as width by drop.
Do not subtract your own allowance from these numbers; most manufacturers deduct a small gap themselves, but follow their instructions.
Measuring for an exact-fit blind
- Decide how much overlap you want at the sides, typically 5 to 10 cm for light blocking.
- Measure the width of the window area, then add overlap to both sides.
- Measure the drop from the fixing point to where you want the blind to end, often the sill or slightly beyond.
- Check there is enough wall for the brackets.
Measuring for curtains
Curtains need two measurements: the width of the track or pole, and the drop.
- Width: curtains look fuller with more fabric, with a common guide being about 1.5 to 2 times the track width.
- Drop: measure from the pole or track to where you want the curtain to finish, for example the sill, below the sill, or floor length.
- Heading type: pencil pleat, eyelet and tab tops use different amounts of fabric.
Keep radiators and furniture in mind. Floor-length curtains over a radiator can trap heat or look awkward.
Window dressing tips
- Fit the track or pole first, and measure from it. How to fit a curtain pole shows how to do that.
- For wide windows, split into several narrower blinds, which are easier to lift and look better.
- Allow room for clearance on windows that open inwards.
Child safety
Blinds with cords can be a strangulation hazard for young children. Choose cordless, or use safety devices to keep cords out of reach and fixed firmly to the wall. This is a particularly important safety point in homes with children, whatever the style.
Common mistakes
- Measuring once and trusting it.
- Using a fabric tape, which stretches.
- Assuming the window is square.
- Forgetting to check the depth for recess fittings.
- Ordering before checking the fixing surface, such as a uPVC frame or plasterboard.
If a window is awkward, a provider can measure and fit in one visit; see how to prepare for an installer visit.
A worked example: a recess blind for a 1,200 mm window
Measure the recess width at three points (top, middle, bottom) and use the smallest figure, and the height at left, middle and right, using the largest figure if the blind will hang to the sill or the smallest if you prefer a gap. Record in millimetres, noting whether you measured to the frame or plaster. Check depth for the brackets, especially with uPVC windows that have shallow frames. Then check with the supplier whether they deduct size for fit or expect your exact measurement.
A short measuring table
| Item | What to measure | Tip |
|---|---|---|
| Recess blind width | Three points, smallest | Allow for handles |
| Recess blind drop | Three points | Check sill or radiator |
| Exact fit width | Frame or glass edge | Measure carefully |
| Curtain pole length | Window plus overlap | Add 15 to 30 cm each side |
| Curtain drop | Pole or track to floor or sill | Allow for pole height |
Things that catch people out
- Radiators or window sills that interfere with drop.
- Window handles that foul the blind roller.
- Different measuring conventions between suppliers.
- Walls that are out of square at the corners.
Before ordering
Take a photo of each window, with a tape visible, and write down measurements immediately. See how to fit a curtain pole for fixing the pole once you have the size, and keep child safety in mind with cords and chains.
Frequently asked questions
Should I measure in millimetres or centimetres?
Millimetres give you more accuracy, and most suppliers prefer them. Write down which unit you use and keep it consistent.
How far below the sill should curtains hang?
Short curtains typically finish a few centimetres below the sill, while floor-length ones hover just above the floor or just touch it.
Can I fit blinds to uPVC windows without drilling?
Some brackets clip onto the frame and need no screws. Check the product guidance for your frame type and the weight of the blind.