How to fit blinds and curtains: the complete measuring and fitting guide

Fitting window dressings is four decisions in order: which product suits the window, recess or face fit, what size to order after deductions, and what the wall above the window is actually made of. The first three decide whether the blind works. The fourth decides whether it stays up.

Measure in millimetres, always with a steel tape, and always three times across the opening — UK window reveals are rarely square, and a 6 mm difference between the top and bottom of a recess is enough to jam a venetian. Everything else in this guide is the detail behind those numbers, including an interactive calculator that does the arithmetic for you. If you would rather hand the whole job over, our blinds and curtains fitting service measures, fits and makes the cords safe in one visit.

Choose the mechanism before you choose the fabric. Each type has a window it is genuinely good at and a window it fails on, and the wrong choice shows up as a blind that will not clear a handle, a stack that eats a third of the glass, or slats that rattle every time the trickle vent is open.

A recess fit (also called an exact or inside fit) sits inside the window reveal. A face fit (outside or exterior fit) mounts on the wall above and beyond the opening. The choice affects the size you order, the fixings you need and how much light gets past.

The default answer for bedrooms is a face fit; the default for kitchens and bathrooms is a recess fit so worktops and tiled sills stay clear. If you are fitting both a blind and curtains, put the blind in the recess and the pole outside it so the two never foul each other.

Take five measurements before you touch the calculator: recess width at the top, middle and bottom; recess drop at the left, centre and right; recess depth from the glass to the front edge of the reveal; and the height from the floor to the top of the recess if you also want curtains. Use the narrowest width and the longest drop.

These are the standard UK trade allowances. They exist because a blind has to run without brushing plaster, and because a face-fit blind has to overlap far enough that daylight cannot cut down the sides.

• Recess drop: measure to the sill and order the exact drop; blinds are not shortened on site.
• Ceiling fixing: add roughly 120 mm to the drop so the blind still covers the opening from a higher start point.
• Tiled reveals: measure to the face of the tile, not the plaster behind it.
• Two blinds side by side: allow a 5 mm gap between them so the barrels do not touch and squeak.

A pole is decorative and sits proud of the wall on visible brackets. A track is functional, discreet and can be bent to follow a bay. Neither is better — they solve different problems.

One rule of thumb: if the pole span exceeds about 2.4 m, or the curtains are interlined, add a centre bracket. Most sagging poles are not weak poles — they are poles carrying two metres of unsupported span.

This is where a competent fit separates itself from a rushed one. Three numbers make a window look considered rather than cramped.

Curtain width is not window width. It is pole length multiplied by a fullness ratio set by the heading style, then divided between the pair.

Choosing the drop

• To the sill: finish 10 mm above it so the hem does not sit on the sill and mark.
• Below the sill: 150 mm below is the standard — the right choice above a radiator.
• To the floor: 15 mm clear of the floor for everyday use, or 20–40 mm of deliberate break for a heavier, more traditional look.
• Measure from the pole: take the drop from the bottom of the ring or glider, not the pole itself, or the curtain will finish 30–40 mm long.

• Steel tape measure — a fabric tape stretches and will cost you a blind.
• Cable and pipe detector — the wall above a window carries more cable runs than people expect.
• Cordless combi drill with a hammer setting for brick and concrete lintels.
• Drill bits: 5.5 mm and 7 mm masonry, HSS for uPVC and timber, and a spear-point or diamond bit for tiles.
• Spirit level (600 mm minimum) or a self-levelling laser for wide windows.
• Fixings: brown plugs for brick, metal spring toggles for plasterboard, through-fixings for dot-and-dab, and 40 mm screws minimum.
• Step ladder with a platform — not a chair, not the sofa arm.
• Chain tensioner or cord cleat — supplied with most blinds and legally expected to be fitted.

Total outlay for a decent kit is roughly £60–£110, which pays for itself against two or three fitted windows. The only tool worth hiring rather than buying is an SDS drill for a concrete lintel, at about £15–£25 a day.

Bay windows

A bay is three or five windows at angles, so treat it as one continuous run, not separate windows. A bendable track fitted to the ceiling or the wall face glides around the angles; a pole needs purpose-made corner connectors, and curtain rings will always hesitate at each joint. Measure each face separately and add the angles; for blinds, order one per pane with a 5 mm gap between them so the barrels never touch.

Sash windows

Original box sashes have deep reveals and often a wooden lining you can screw straight into — the easiest fixing in any period home. Watch for the sash cords and pulley boxes at the top corners of the reveal: drilling into a pulley stile can foul the weight. Keep recess brackets to the centre of the head lining and away from the outer 60 mm.

uPVC and tilt-and-turn

Do not drill uPVC unless you have to; a perforated frame can void the window guarantee and lets water into the chamber. Perfect-fit blinds clip into the bead and move with the sash, which is the only sensible answer on a tilt-and-turn. Where a drilled fixing is unavoidable, go into the reinforced steel chamber with a self-tapping screw and seal the hole.

Every internal blind supplied or installed in the UK has to be safe by design under BS EN 13120. In practice, that means no accessible cord or chain loop can be left hanging where a small child can reach it. This is the step most DIY fits skip, and it is the one that matters most.

• Fit the supplied chain tensioner screwed to the wall or frame — not left in the packet.
• Use a breakaway connector on any looped cord so it separates under load.
• Where a cleat is used, mount it at least 1.5 m above the floor and wrap the cord every single time.
• Never place a cot, bed, sofa, changing table or bookcase where a child can climb to a cord.
• In bedrooms and nurseries, prefer cordless, motorised or spring-loaded blinds outright.

Window dressings do real thermal work. Roughly a fifth of the heat in an average UK home leaves through the glazing, and what you hang over it changes both the heat loss and the condensation risk.

• Interlined, floor-length curtains that sit close to the wall are the best insulator available short of new glazing — they trap still air against the glass.
• Cellular (honeycomb) blinds are the best-performing blind for insulation, because the cells hold air.
• Never draw a full-length curtain over a radiator. It funnels warm air straight up the cold glass and out. Stop the curtain 150 mm below the sill instead.
• Condensation and mould: a tightly sealed blind left down all day traps moist air against cold glass. Open blinds daily and leave a trickle vent open in bedrooms.
• Blackout: only a face fit with generous overlap, or a blackout blind plus lined curtains, gives genuine darkness — a recess-fit roller always leaks at the edges.

• Measuring in inches or with a fabric tape, then converting badly.
• Measuring one width instead of three and missing an out-of-square reveal.
• Deducting 10 mm when the supplier already deducts it.
• Ignoring recess depth and finding a roman blind stack sitting over the glass.
• Forgetting the window handle, so the blind cannot come down.
• Fixing a pole into bare plasterboard with plastic plugs.
• Setting the pole tight to the recess so the open curtain covers half the glass.
• Measuring the curtain drop from the pole rather than the bottom of the ring.
• Drilling above a window without scanning for cables.
• Leaving the chain tensioner in the bag.

Prices rise for concrete lintels needing an SDS drill, lath-and-plaster walls, tiled reveals, working above a stairwell, and anything over about 2.5 m where access equipment is needed. They fall when several windows are done in one visit, which is why a whole-house fit-out costs far less per window than four separate call-outs.

Greater Manchester housing stock makes this job unusually varied, and the right approach changes street by street.

• Mill and warehouse conversions in Ancoats, the Northern Quarter and Castlefield have huge cast-iron or steel-framed windows, concrete soffits and floor-to-ceiling glass. Expect an SDS drill, ceiling-fixed track, and very long drops that need two people.
• Victorian and Edwardian terraces in Chorlton, Levenshulme, Whalley Range and Didsbury have deep bays with box sashes. Bendable track around the bay and a timber head lining to fix into is the usual answer.
• Post-war and new-build estates in Wythenshawe, Salford Quays, Hulme and parts of Oldham are dry-lined or dot-and-dab, so poles need through-fixings that reach the blockwork behind the plasterboard.
• uPVC replacement windows are near-universal across Bolton, Bury, Rochdale, Wigan, Tameside and Stockport semis — perfect-fit blinds avoid drilling the frames and keep window guarantees intact.
• Access and parking: apartment blocks around Deansgate and MediaCity need loading bay booking, and many terraced streets in Salford and Trafford are permit-only, so we plan arrival times around it.

You can see coverage, local window profiles and prices on the Greater Manchester blinds and curtains fitting hub, which links through to every area we cover.