How much fabric for curtains? Take your track width, multiply by the fullness ratio, add 25cm for returns and overlap, divide by the fabric width minus 20cm, and round up - that is your number of widths. Multiply by the cut drop, which is the finished drop plus 30cm. A 150cm track with a 220cm floor-length drop needs 7.5m of 150cm cloth.
Curtains are the one project where getting the metreage wrong is genuinely expensive, because you are buying in units of five to fifteen metres rather than two. They are also the project where cheap cloth changes the answer most dramatically: at £18 a metre a lounge pair is a considered purchase, and at around a pound a metre from the drape fabrics range it is a Saturday afternoon. So here is the whole calculation, term by term, with three complete rooms costed at the end.
The formula, stated plainly
Everything below is an elaboration of these five lines.
The curtain formula
1. Flat width needed = track width × fullness ratio + 25cm (returns and overlap)
2. Usable width per drop = fabric width − 20cm (side hems and joining seams)
3. Number of widths = line 1 ÷ line 2, rounded up
4. Cut drop = finished drop + 30cm (heading + hem, pencil pleat)
5. Metres to buy = widths × cut drop ÷ 100
Term by term:
- Track width. The pole or track itself, measured after it is fitted. Not the window.
- Fullness ratio. How much flat cloth you want gathered into that width. 2.0 to 2.5 for most headings. Table below.
- Returns and overlap. On a track, the curtain wraps back to the wall at each end (a "return", 7–10cm each) and the two curtains cross in the middle (an "overlap", about 10cm). Together, 25cm. On a pole with rings, allow 10cm for the centre and nothing for returns.
- Fabric width minus 20cm. Double 5cm side hems eat 10cm of cloth at each edge. Where you join widths together you use seam allowances instead, so this figure is slightly generous on joined panels - which is what you want.
- Cut drop. Finished drop plus a heading allowance and a hem allowance. For pencil pleat that is about 10cm and 20cm respectively, so plus 30cm. Other headings, see below.
Round the final metreage up to the next half metre. Every curtain maker does. If the cloth is cotton or linen and the curtains will ever be washed, pre-wash it before you cut - why some fabrics shrink explains what to expect.
Measuring properly: track vs pole, sill vs floor
Fit the track or pole first, then measure. Buying fabric off a window measurement is the single most common way to end up 1.5m short.
Width
- A track or pole should extend 15cm past the window frame at each side, so the drawn curtains stack against the wall rather than over the glass. That is 30cm more than the window.
- On a pole, measure between the finials and ignore the finials themselves.
- On a track, measure the full length of the track including any curved returns.
- A track or pole should also sit 10–15cm above the frame, which raises the drop.
Drop
- From a track: measure from the top of the track. The hooks sit in the tape, and the tape sits just above the track, so the curtain effectively starts there.
- From a pole: measure from the bottom of the ring eye, where the hook will sit - not from the pole itself.
- Sill length: finish 1cm above the sill.
- Below sill: sill height plus 15cm, so the curtain clears the radiator or the sill nose.
- Floor length: finish 1cm above the floor. Anything closer and the curtain will drag and dirty; anything further and it looks short.
- Puddled: floor measurement plus 15–20cm. Only worth it in a room where nobody walks the perimeter.
Measure the drop in three places - left, centre, right. Old houses are not square, and a 3cm difference across a bay is normal. Use the longest and let the hem take up the difference.
Fullness ratios by heading type
| Heading | Fullness | Add to drop (heading + hem) | Notes |
|---|---|---|---|
| Gathered tape, 25mm | 1.5–1.8× | +25cm | Cheapest and flattest. Fine for a small kitchen window, thin on a big one. |
| Pencil pleat tape, 75mm | 2.0–2.5× | +30cm | The UK default. Use 2.5× on a light cloth, 2.0× on a heavy one. |
| Deep pencil pleat, 150mm | 2.5× | +38cm | For drops over 230cm, where a shallow heading looks mean. |
| Eyelet | 2.0–2.2× | +35cm | Needs an even number of eyelets per curtain so it closes facing the right way. |
| Tab top or tie top | 1.5–1.8× | +30cm plus tabs | Flat, casual, and it does not draw well. Best for curtains you leave open. |
| Pinch pleat, double | 2.0–2.2× | +40cm | Buckram in the heading, so the top allowance is deeper. |
| Pinch pleat, triple (French) | 2.25–2.5× | +40cm | The dressiest. Also the hungriest. |
| Wave | 2.0–2.2× | +30cm | Requires a wave track and matching cord tape. Not retrofittable. |
| Slot top / café | 1.5–2.0× | +2× rod circumference +10cm | Sewn channel. Cannot be drawn without pulling. |
Pick fullness by cloth weight, not by taste. A 2.5× pencil pleat in a heavy cotton twill will not fold, it will bunch, and it will strain the track. A 2.0× pencil pleat in a light voile will look starved. Heavy velvet sits best at the bottom of the range. If you are undecided on the cloth itself, choosing curtain fabrics for every room works through weight against room by room.
Hems and headings: what to add and why
- Bottom hem: a double 10cm turn, so add 20cm. Deep hems are not decoration — the weight is what makes a curtain hang straight instead of kicking out at the bottom. They also give you 10cm of lengthening if you move house.
- Heading: 10cm for pencil pleat tape, up to 20cm for pinch pleat with buckram. See the table.
- Side hems: a double 5cm turn each side, which is 10cm of cloth per side and 20cm off the usable width per drop.
- Joining seams: 1.5cm each side of every join. The 20cm-per-width allowance absorbs these.
- Lining hem: smaller. Add 15cm to the finished drop for the lining — 5cm at the top, a double 5cm hem at the bottom. Lining should finish about 2cm shorter than the face fabric so it does not peep.
You do not have to round up to an even number of widths. The advice you will read everywhere is to round widths up to the next even number so each curtain gets the same whole number. That is wrong as often as it is right. If the calculation says 3.08 widths, going to 4 gives you 3.5× fullness on a 2.5× heading — heavy, expensive and it will not stack. The trade answer is half widths: use 3 widths, cut one down the middle, and give each curtain one and a half. The join goes to the outer edge where nobody looks. That decision saves 2.5m on the bedroom example below.
Pattern repeat: the expensive bit
If your fabric has a repeating design, every drop must be cut so the pattern sits at the same height on every panel. Otherwise the motifs stagger across the pair and it looks like a mistake, because it is one.
The method:
- Work out your cut drop as normal.
- Round it up to the next whole multiple of the repeat. If the cut drop is 300cm and the repeat is 32cm, then 32 × 9 = 288cm which is short, and 32 × 10 = 320cm which is not. Your cut drop becomes 320cm.
- Multiply the new cut drop by the number of widths.
- Add one extra repeat to the total, so you have room to position the first cut where the pattern falls well at the hem.
The premium is roughly half a repeat per drop on average, so a big repeat on a lot of widths is where curtains get expensive. If you are still deciding between a print and a plain, plain vs printed fabrics weighs up both. There is one consolation: because you are rounding up to a whole repeat anyway, a deeper heading allowance is often free. Going from a 30cm allowance to a 40cm allowance on the example above changes nothing at all - both round to the same 320cm.
Check the repeat on the curtain fabric listing before you buy. If it is not stated, measure the height of one full motif on the swatch photograph against the stated width and take that as your working figure, then add a repeat for safety.
Three worked examples, costed
Fabric at indicative rates of £1 and £3 a metre; haberdashery at indicative high-street prices at the time of writing. Our prices vary by range and change — check the listing for what a given cloth costs today.
Example 1: small kitchen window, unlined
Pole 90cm, sill-length drop 90cm, pencil pleat at 2.0×, plain cotton on a 115cm bolt.
- Flat width: 90 × 2.0 = 180cm, plus 10cm for the centre overlap = 190cm
- Usable width per drop: 115 − 20 = 95cm
- Widths: 190 ÷ 95 = 2 widths (one per curtain, no joins)
- Cut drop: 90 + 30 = 120cm
- Fabric: 2 × 1.2m = 2.4m
Delivered fullness is 2 × 95 = 190cm over a 90cm pole, which is 2.1×. Correct for pencil pleat.
| Item | Quantity | At £1/m fabric | At £3/m fabric |
|---|---|---|---|
| Main fabric | 2.4m | £2.40 | £7.20 |
| Pencil pleat tape | 2.0m | £3.00 | £3.00 |
| Hooks | 14 | £1.00 | £1.00 |
| Thread | 1 reel | £1.50 | £1.50 |
| Total | £7.90 | £12.70 |
Example 2: standard bedroom, lined
Track 150cm, floor-length drop 220cm, pencil pleat at 2.5×, plain cotton on a 150cm bolt, cotton-sateen lined.
- Flat width: 150 × 2.5 = 375cm, plus 25cm returns and overlap = 400cm
- Usable width per drop: 150 − 20 = 130cm
- Widths: 400 ÷ 130 = 3.08, so 3 widths using one half width per curtain
- Cut drop: 220 + 30 = 250cm
- Main fabric: 3 × 2.5m = 7.5m
- Lining cut drop: 220 + 15 = 235cm; lining: 3 × 2.35m = 7.05m, so buy 7.1m
Delivered fullness is 3 × 130 = 390cm over a 150cm track, which is 2.6×. Rounding up to 4 whole widths instead would have given 520cm, a fullness of 3.5×, and cost 10m rather than 7.5m — an extra 2.5m of fabric and 2.4m of lining for a heading that would be too dense to stack neatly.
| Item | Quantity | At £1/m fabric | At £3/m fabric |
|---|---|---|---|
| Main fabric | 7.5m | £7.50 | £22.50 |
| Lining (indicative £1.50/m) | 7.1m | £10.65 | £10.65 |
| Pencil pleat tape | 3.0m | £4.50 | £4.50 |
| Hooks | 30 | £2.00 | £2.00 |
| Thread | 2 reels | £3.00 | £3.00 |
| Total | £27.65 | £42.65 |
A ready-made lined pencil-pleat pair at roughly that size is indicatively £60 to £120 at the time of writing. Note where the money has gone: at £1 a metre the lining costs more than the curtain.
Example 3: full-height lounge, patterned and lined
Track 220cm, floor-length drop 260cm, triple pinch pleat at 2.25×, printed cotton on a 150cm bolt with a 32cm vertical repeat, lined.
- Flat width: 220 × 2.25 = 495cm, plus 25cm = 520cm
- Usable width per drop: 130cm
- Widths: 520 ÷ 130 = exactly 4 widths, two per curtain, all whole — ideal for a print
- Cut drop before repeat: 260 + 40 (pinch pleat) = 300cm
- Repeat adjustment: 32 × 9 = 288cm (short), 32 × 10 = 320cm. Cut drop becomes 320cm
- Main fabric: 4 × 3.2m = 12.8m, plus one repeat (0.32m) = 13.12m, so buy 13.2m
- Lining cut drop: 260 + 15 = 275cm; lining: 4 × 2.75m = 11.0m
Delivered fullness is 4 × 130 = 520cm over a 220cm track, which is 2.36×. Comfortably inside the pinch pleat range, and it landed on whole widths, which means the print sits symmetrically on every panel.
| Item | Quantity | At £1/m fabric | At £3/m fabric | At £15/m fabric |
|---|---|---|---|---|
| Main fabric, 32cm repeat | 13.2m | £13.20 | £39.60 | £198.00 |
| Same curtains in a plain cloth | 12.0m | £12.00 | £36.00 | £180.00 |
| Cost of the repeat | 1.2m | £1.20 | £3.60 | £18.00 |
| Lining (indicative £1.50/m) | 11.0m | £16.50 | £16.50 | £16.50 |
| Pinch pleat tape | 5.5m | £9.00 | £9.00 | £9.00 |
| Hooks and thread | — | £5.00 | £5.00 | £5.00 |
| Total | £43.70 | £70.10 | £228.50 |
The £15 column is there to make the point. The pattern repeat costs you £1.20 on cheap cloth and £18.00 on expensive cloth, for exactly the same 1.2m of fabric. Which is why big prints and generous fullness are decisions you can actually make here, rather than compromises you talk yourself out of. The same reasoning applies to every large-area project — there is a broader treatment in the guide to how much fabric you need.
Lining: when you need it and how much
Line a curtain if any of these apply: the room faces south and the fabric will fade; the cloth is light enough to show the sun through the weave; you want the curtain to hang with weight rather than flap; or it is a bedroom. Skip it on kitchen and bathroom curtains, on voiles, and on anything you want light to come through.
Quantities are straightforward: the same number of widths as the face fabric, at a cut drop of finished drop plus 15cm. Standard cotton-sateen lining comes at 137cm or 150cm; check which, because a 137cm lining behind a 150cm face fabric changes your usable width to 117cm and can push you up a whole width. That is the most common lining mistake.
- Standard lining: cotton sateen, cream or white. Adds body, blocks fading.
- Thermal lining: an acrylic-foam coated back. Noticeably heavier — check your track's stated weight limit.
- Blackout lining: usually a three-pass coating. Genuinely dark, and stiff, so drop your fullness to the bottom of the range or the pleats will not fold cleanly. Pin-holes from over-handling let light through, so handle it once.
- Interlining: a soft bump layer between face and lining. Adds real luxury and real weight, and is a considerable step up in construction. Same metreage as the lining. Lining vs interlining covers when the extra layer is worth it.
Browse lining fabrics for what is in stock, and buy the lining in the same order as the face fabric so the whole project arrives together.
Cushions and roman blinds
Cushion covers
Cut the front 1cm larger than the pad in each direction for a plump finish, and cut two backs each the pad width by roughly 60 per cent of its height, which gives an overlap. Furnishing fabrics wear better on cushions than dress cottons.
| Pad size | Cut pieces | Fabric at 150cm | Fabric at 115cm | At £1/m | At £3/m |
|---|---|---|---|---|---|
| 40cm | Front 41 × 41; backs 2 × (41 × 30) | 0.5m | 0.8m | £0.50 | £1.50 |
| 45cm | Front 46 × 46; backs 2 × (46 × 33) | 0.5m | 0.8m | £0.50 | £1.50 |
| 50cm | Front 51 × 51; backs 2 × (51 × 36) | 0.9m | 0.9m | £0.90 | £2.70 |
| 60cm | Front 61 × 61; backs 2 × (61 × 42) | 1.1m | 1.5m | £1.10 | £3.30 |
| 46in / 117cm floor | Front 118 × 118; backs 2 × (118 × 71) | 2.6m | Cannot be cut | £2.60 | £7.80 |
The jump between 45cm and 50cm is the interesting one. Three 46cm-wide pieces side by side come to 138cm and fit across a 150cm bolt in a single row, so a 45cm cover takes half a metre. Three 51cm pieces come to 153cm and do not, so a 50cm cover needs two rows and 0.9m. Five centimetres of pad costs you 80 per cent more fabric. If you are buying pads as well as cloth, that is worth knowing before you choose.
Roman blinds
Cut width = finished width + 10cm. Cut drop = finished drop + 20cm. A blind for a 100cm-wide recess with a 140cm drop therefore needs a piece 110 × 160cm: 1.6m of 115cm fabric, at £1.60 at an indicative pound a metre, plus 1.6m of lining. Space the rod pockets 25–30cm apart, which is five for a 140cm drop.
Watch the width. A finished blind over about 105cm cannot be cut from a 115cm bolt once you have added the turnings, so move up to 150cm cloth. Blinds also want a firmer hand than curtains — something from the upholstery fabric end holds a fold far better than a dress cotton, and the same durability logic that applies to upholstery fabric that lasts applies here.
One last quantity while you are ordering for a room: a throw to match, 130 × 180cm finished, takes 1.9m of 150cm cloth — £1.90 at an indicative pound a metre.
Frequently asked questions
How much fabric do I need for curtains?
Multiply track width by the fullness ratio, add 25cm for returns and overlap, divide by the fabric width minus 20cm and round up — that is your number of widths. Multiply by the cut drop, which is the finished drop plus 30cm. A 150cm track at a 220cm drop needs about 7.5m of 150cm fabric.
How do you calculate curtain fullness?
Fullness is the flat width of finished curtain divided by the track width. Pencil pleat wants 2.0 to 2.5 times, eyelet 2.0 to 2.2, pinch pleat 2.0 to 2.5, tab top 1.5 to 1.8. A 150cm track at pencil pleat fullness therefore needs 300cm to 375cm of flat cloth before hems.
How much fabric for a 46 inch cushion cover?
A 46in floor cushion is 117cm. Cut a front of 118 × 118cm and two backs of 118 × 71cm. Only one 118cm piece fits across a 150cm bolt, so you need 2.6m — £2.60 at an indicative pound a metre. It cannot be cut from 115cm cloth without joining. A 46cm cushion takes just 0.5m.
Do I measure the window or the track?
The track or pole, always. A track should extend 15cm past the frame at each side so the curtains stack clear of the glass, which makes the window measurement 30cm short. Fit the track first, measure it, then buy fabric. Measure the drop in three places and use the longest.
How much extra fabric do I need for a pattern repeat on curtains?
Round each cut drop up to the next whole multiple of the repeat, then add one extra repeat to the total. On a 300cm cut drop with a 32cm repeat, each drop becomes 320cm, and four widths plus one repeat is 13.2m rather than 12m — roughly a 10 per cent premium.
