Curtain Math Made Easy: How Much Fabric Do I Actually Need?
Fabric Guides · Curtain Making
Curtain Math Made Easy:
How Much Fabric Do I Actually Need?
"I'll just guess how much I need." Famous last words — followed by a frantic re-order that doesn't quite match the dye lot.
Ordering curtain fabric feels harder than it should be. Too little and you're scrambling. Too much and you've wasted money. The good news? There's a simple formula — and once you know it, you'll never second-guess an order again.
This guide breaks it down window by window, fabric type by fabric type. By the end, you'll know your exact metre count before you even open the shop.
×2.5
Minimum fullness ratio for standard curtains
+20cm
Always add for hem & heading allowance
+1
Extra pattern repeat to buy — every single time
Step One
The Formula Every UK Home Sewer Needs
Whether you're dressing a bay window or a single sash, the calculation is always the same. Measure once, order right — no guesswork, no drama.
The Standard Curtain Fabric Formula
Total Fabric (m) = (Track Width × Fullness) ÷ Fabric Width
× Number of drops
+ Hem & Heading (20–30cm per drop)
+ Pattern Repeat (1 full repeat extra per drop)
Fullness guide: Pencil pleat = ×2.5 | Eyelet = ×2 | Pinch pleat = ×2.5 | Tab top = ×1.5
Most curtain fabric from Discount Fabrics Ltd is 137–140cm wide — use 137cm in your calculations to stay safe.
UK pro tip: Always round up to the nearest half metre when ordering. If your calculation gives you 4.3m — order 4.5m. The small cost is nothing compared to a mismatched top-up order weeks later.
Step by Step
How to Measure Your Window in 4 Steps
01
Measure the Track or Pole Width
Measure the full length of your track or pole — not the window frame. Curtains need to extend 15–20cm past the frame on each side to block light properly.
Add 15–20cm each side of the frame02
Measure the Drop
Measure from the top of the track down to where you want the curtain to end. Floor-length: stop 1cm above the floor. Add 15cm at the top (heading) and 10–15cm at the bottom (hem).
Always measure from the track, not the window03
Apply the Fullness Multiplier
Flat fabric looks flat. Multiply your track width by your chosen fullness ratio. Divide by the fabric width to find your number of widths. Always round up — never down.
Round widths up — never down04
Add the Pattern Repeat
The step most beginners skip — and regret. If your fabric has a pattern repeat (e.g. 32cm), every cut length must start at the same point. Add one full repeat per width you're cutting.
Check the product page for repeat sizeWorked Example: A Standard UK Living Room Window
- Track width: 160cm → ×2.5 fullness = 400cm of fabric width needed
- Fabric is 137cm wide → 400 ÷ 137 = 2.9 → round up to 3 widths
- Drop: 230cm + 30cm allowance = 260cm → 3 × 2.6m = 7.8m
- Pattern repeat: 28cm → 3 × 0.28m = 0.84m → round up to +1m
- Total order: 9 metres — rounded up from 8.64m for peace of mind
Quick Reference
Heading Style Cheat Sheet
Not sure which heading type you're making? Here's how they differ — and what that means for your fabric order.
| Heading Style | Fullness Needed | Best Fabric Type | Difficulty |
|---|---|---|---|
| Eyelet / Ring Top | ×2 – ×2.5 | Cotton, linen, velvet | Beginner |
| Pencil Pleat | ×2.5 – ×3 | Most fabrics — very versatile | Beginner |
| Pinch Pleat | ×2 – ×2.5 | Structured cotton, linen | Intermediate |
| Tab Top | ×1.5 – ×2 | Lighter fabrics — voile, cotton | Beginner |
| Wave / S-Fold | ×2 – ×2.3 | Linen, cotton, sheer blends | Intermediate |
| Goblet Pleat | ×2.5 | Medium–heavyweight, velvet ideal | Advanced |
Choosing Your Fabric
Which Curtain Fabric Is Right for Your Room?
🪟
Cotton & Polycotton
The most versatile choice. Holds structure well, easy to sew, and comes in every colour and print imaginable. Perfect for bedrooms and living rooms year-round.
Width: typically 137–140cm🌿
Linen & Linen Blends
The relaxed, natural look that never dates. Linen drapes beautifully in a wave heading and softens with washing. Best for living rooms and kitchens with natural light.
Allow extra: linen shrinks ~3–5%🌙
Velvet & Chenille
Heavyweight luxury. Adds warmth, blocks light, and creates true drama. Perfect for formal sitting rooms and bedrooms. Use a pinch or goblet pleat to show it off.
Cut all drops in the same direction☀️
Voile & Sheer
Layer over a blackout lining or use as a standalone privacy screen. Lightweight sheers need even more fullness — go up to ×3 for a lush gathered look.
Fullness: ×2.5–3 recommendedDon't forget lining. An interlining protects your fabric from UV fading, improves drape, and adds insulation. For blackout lining, measure exactly the same as your curtain fabric — it cuts to the same dimensions.
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