How Many Litres of Paint Do I Need Calculator
Work in metres and litres throughout: multiply wall perimeter by height for gross area, subtract standard door and window sizes, then divide by a 2-coat effective coverage rate of around 12-16 square metres per litre depending on your paint.
Quick Answer
Work in metres and litres throughout: multiply wall perimeter by height for gross area, subtract standard door and window sizes, then divide by a 2-coat effective coverage rate of around 12-16 square metres per litre depending on your paint.
How Many Litres of Paint Do I Need Calculator
Enter your values below for an instant result, then see the formula, worked example, and common mistakes.
Enter your values and click calculate.
How to Use This Calculator
Measure room length, width, and wall height in metres to match how paint coverage is published in most litre-based markets.
A standard interior door opening is about 1.85 m2 and a standard window about 1.5 m2 — enter how many of each so they can be subtracted from the paintable area.
Most emulsion paints cover roughly 12-16 m2 per litre per coat; the default of 13 m2/litre already accounts for a 2-coat job on a typical wall, but check your specific product’s stated coverage.
Paint is sold in fixed container sizes (1L, 2.5L, 5L, 10L) — always round your calculated litres up to a size (or combination of sizes) you can actually buy.
Formula
Litres needed = [(Perimeter x Height) – (Windows x 1.5 m2) – (Doors x 1.85 m2)] / Coverage per litre.
Reference Table: Typical Deductions and Coverage (Metric)
| Item | Typical value |
|---|---|
| Standard door opening | ~1.85 m2 |
| Standard window | ~1.5 m2 |
| Emulsion paint coverage, single coat | ~12-16 m2/litre |
| Emulsion paint coverage, 2-coat effective | ~6-8 m2/litre effective (or divide total area x2 coats by single-coat rate) |
Common Mistakes to Avoid
- Mixing up single-coat and 2-coat coverage rates — always confirm whether the coverage number you are using already accounts for multiple coats or not.
- Forgetting to deduct door and window area, leading to over-buying paint.
- Using a US gallon-based coverage figure without converting it to the litre/m2 system, causing large errors.
- Not rounding up to an actual purchasable container size (1L, 2.5L, 5L, 10L) and ending up short mid-job.
When the Estimate May Be Wrong
Coverage varies by paint brand, finish (matte vs silk/satin), wall texture, and porosity. Textured or unprimed new plaster can absorb noticeably more paint than the stated coverage rate, so treat this as a starting estimate and round up, especially for a first coat on new or repaired walls.
FAQs
How many litres of paint do I need for a room?
It depends on wall area and coverage, but as a rough guide, a small bedroom (about 30-35 m2 of net wall area) typically needs 2-3 litres for a 2-coat job with standard emulsion.
How much area does a litre of paint cover?
Most emulsion paints cover roughly 12-16 square metres per litre per coat, though this varies by brand and surface.
Should I deduct doors and windows before calculating paint quantity?
Yes — a standard door is about 1.85 m2 and a standard window about 1.5 m2, and subtracting them avoids buying more paint than needed.
Sources and Methodology
Metric door/window deduction sizes and emulsion paint coverage ranges (12-16 m2/litre per coat) reflect commonly published UK/European decorating industry guidance as of 2026. Confirm exact coverage on your specific paint product before final purchase.
