How Much Curtain Fabric Do You Need?
This calculator tells you exactly how many centimeters of fabric you need to sew or order curtains for a single window. It uses the industry-standard fullness-and-hem formula: Total Fabric = (Window Width × Fullness Multiplier) + Curtain Length + Hem/Header Allowance. For a standard pair of panels with 2× fullness and a 10 cm combined allowance for top header and bottom hem, the formula collapses to (Width × 2) + Length + 10 cm. Use it whenever you're buying fabric by the meter, planning a DIY sewing project, or quoting materials for a client window-treatment job.
When to use this calculator
- Buying fabric at a store for a DIY sewing project — knowing the exact centimeters prevents buying too little or wasting money on excess yardage.
- Quoting material costs for a home-renovation or interior-design client who needs curtains on multiple windows with different widths and drop lengths.
- Planning blackout or thermal curtains where fabric is expensive ($15–$40/yd) and precise measurement directly controls project budget.
- Ordering patterned fabric online where pattern repeat adds extra length requirements — using the base formula first, then adding repeat length per panel.
Sample Calculation
- Window Width: 150 cm, Curtain Length: 250 cm
- Formula: (150 × 2) + 250 + 10 = 560 cm
How it works
3 min readHow It Is Calculated
The calculator applies the standard curtain-fabric formula used by professional seamstresses and window-treatment retailers:
Total Fabric (cm) = (Window Width × Fullness) + Drop Length + AllowancesWith default settings (2× fullness, 10 cm header + hem allowance):
Total Fabric (cm) = (Window Width cm × 2) + Curtain Length cm + 10Term definitions:
Worked example — calculator default:
---
Reference Table
| Window Width (cm) | Curtain Length (cm) | Fullness | Allowance (cm) | Total Fabric (cm) |
|---|---|---|---|---|
| 90 | 150 | ×2 | 10 | 340 |
| 120 | 200 | ×2 | 10 | 450 |
| 150 | 250 | ×2 | 10 | 560 |
| 180 | 250 | ×2 | 10 | 620 |
| 200 | 270 | ×2 | 10 | 680 |
| 150 | 250 | ×2.5 | 10 | 635 |
| 150 | 250 | ×3 | 10 | 710 |
| 120 | 200 | ×1.5 | 10 | 390 |
> Tip: For patterned fabric, add one full pattern repeat (typically 25–64 cm) per panel cut to ensure motifs align across panels.
---
Typical Cases
Case 1 — Standard Living Room Window (150 × 250 cm)
Rod width: 150 cm | Floor-length drop: 250 cm | Standard ×2 fullness | 10 cm allowance.
(150 × 2) + 250 + 10 = 560 cm → 5.6 mAt $8/meter for mid-range cotton-blend fabric, material cost = ~$44.80.
Case 2 — Narrow Bedroom Window with Sheer Fabric (90 × 200 cm, ×2.5 fullness)
(90 × 2.5) + 200 + 10 = 435 cm → 4.35 mSheer voile typically costs $4–$6/meter → material cost = ~$17–$26.
Case 3 — Wide Picture Window (200 × 270 cm, ×2 fullness, patterned fabric with 30 cm repeat)
Base fabric:
(200 × 2) + 270 + 10 = 680 cmPattern repeat addition (2 panels × 30 cm):
680 + 60 = 740 cm → 7.4 mPatterned upholstery-weight fabric at $18/m → material cost = ~$133.
---
Common Mistakes
1. Measuring the glass pane instead of the rod or track — The rod is almost always wider than the glass (by 15–30 cm per side), so measuring only the glass can leave you 30–60 cm short of fabric.
2. Forgetting the fullness multiplier — Buying fabric equal to the window width produces flat, skimpy-looking curtains. The ×2 minimum is universally recommended for a gathered appearance.
3. Ignoring pattern repeat — Patterned fabrics require extra yardage per panel (one full repeat per cut) so that horizontal motifs line up. Skipping this causes mismatched panels.
4. Confusing "curtain length" with "window height" — Curtain drop is measured from the rod, which is typically 10–15 cm above the window frame, not from the frame itself. Using window height instead of drop underestimates length.
5. Not accounting for lining fabric — If curtains are to be lined (blackout or thermal lining), the lining requires its own fabric calculation — typically the same length but slightly narrower (rod width × 1.5 instead of × 2).
6. Rounding down instead of up — Always round fabric quantities up to the nearest 10 cm or half-meter when ordering, since fabric stores cut to fixed increments and running short mid-project means buying a new dye lot that may not match.
---
Related Calculators
For other home-improvement measurement needs, explore these tools on Hacé Cuentas:
Frequently asked questions
Why does the formula multiply window width by 2?
The ×2 multiplier is the industry-standard 'fullness ratio' for a gathered curtain look. A single flat panel equal to the window width would look stiff and sparse; doubling the width creates the classic soft folds. Professional window-treatment guides recommend ×1.5 for minimal gather, ×2 for standard pleats, and ×2.5–×3 for full, luxurious sheers.
What does the +10 cm allowance cover?
The 10 cm covers two structural elements: a 4–5 cm double-fold hem at the bottom (folded twice to hide raw edges and add weight) and a 3–4 cm rod-pocket or header at the top through which the curtain rod passes. Some styles with decorative pleated headers may need 15–20 cm instead of 10 cm.
How do I measure curtain drop (length) correctly?
Measure from the bottom of the curtain rod (or the clip/ring bottom if using rings) down to your desired finish point — window sill, 10–15 cm below the sill, or floor. Do NOT measure from the window frame. Rod placement is typically 10–15 cm above the frame, and this 'high hang' technique is widely recommended by interior designers to make windows appear taller.
Does patterned fabric need extra yardage?
Yes. For patterned fabric, add one full pattern repeat length per cut panel. Common repeat sizes range from 25 cm (small prints) to 64 cm (large medallion or floral prints). For example, if your base calculation gives 560 cm across 2 panels, and the repeat is 30 cm, add 2 × 30 = 60 cm, making your order 620 cm (6.2 m). Always ask the retailer for the repeat measurement before purchasing.
Does lining require a separate fabric calculation?
Yes. Lining fabric is calculated separately. A standard lining typically uses 1.5× window width (less gather than the face fabric) and the same drop length plus hem allowance. For a 150 cm wide window with 250 cm drop, lining fabric would be approximately (150 × 1.5) + 250 + 10 = 485 cm (4.85 m). Blackout lining adds $3–$8 per meter over standard cotton lining.
How does fullness affect the look and fabric cost?
Higher fullness multipliers create richer folds but significantly increase fabric use and cost. For a 150 cm × 250 cm window: ×1.5 fullness = 485 cm; ×2 = 560 cm; ×2.5 = 635 cm; ×3 = 710 cm. At $10/m, the difference between ×1.5 and ×3 is 225 cm = 2.25 m = $22.50 more — per window. Multiply that across an entire home and fullness choice becomes a significant budget decision.
Should I measure in centimeters or inches, and does it matter?
This calculator uses centimeters, the standard unit for fabric measurement in most of the world, including among US fabric retailers who sell by the yard (1 yard = 91.44 cm). To convert your result to yards, divide total cm by 91.44. For example, 560 cm ÷ 91.44 = 6.12 yards. Always confirm which unit your supplier uses before placing an order to avoid costly conversion errors.
Can I use this calculator for tab-top or eyelet curtains?
Yes, with a slight adjustment. Tab-top and eyelet (grommet) styles are usually designed with ×1.5–×2 fullness and have minimal header allowance (the tabs or grommets are part of the panel itself). Use ×1.5 as the fullness multiplier and reduce the header allowance to 5 cm for the top fold-over. The rest of the formula remains identical.