Paint Calculator — Litres, Gallons & Tins Needed
Calculate how much paint you need for walls, ceilings and trim. Enter room dimensions or total area, choose the number of coats, and get the exact litres or gallons required — with can size recommendations to minimise waste.
How the paint calculator works
- 1Wall area: (2 × length + 2 × width) × height
- 2Subtract doors (approx. 1.8 m² each) and windows (approx. 1.2 m² each)
- 3Add ceiling area if painting: length × width
- 4Litres needed: area ÷ spreading rate (typically 10–12 m²/L) × number of coats
- 5Spreading rate varies: matte paint 10–12 m²/L, gloss 8–10 m²/L, primer 6–8 m²/L
- 6Round up to the nearest can size to avoid partial-tin waste
Worked example
Bedroom: 4 × 3.5 m, walls 2.4 m high, one door and one window. Two coats of matte emulsion (11 m²/L).
Wall area: 35.52 m² − 3.0 m² = 32.52 m². Two coats: 65.04 m² ÷ 11 = 5.9 L. Buy two 3 L tins or one 5 L tin plus one 2.5 L tin.
Frequently asked questions
How much paint do I need for a 12×12 room?
A 12×12 ft (3.66×3.66 m) room with 8 ft (2.44 m) ceilings has approximately 29 m² of wall area. For two coats at 11 m²/L: 5.3 L. Buy two 2.5 L tins.
How many m² does a litre of paint cover?
Typically 10–12 m² per litre for matte and eggshell wall paint. Gloss and satinwood covers 8–10 m²/L. Primer covers 6–8 m²/L. Always check the product data sheet for the exact spreading rate.
How many coats of paint do I need?
New plaster or a significant colour change: 3 coats (primer + 2 top coats). Repainting a similar colour: 2 coats. Repainting the same colour: 1–2 coats depending on coverage.
Should I use primer before painting?
Yes — always prime new plaster, bare wood, repaired areas and when changing from a dark to a light colour. Primer seals the surface, improves adhesion and reduces the number of top coats needed.
What is the difference between matte, eggshell and gloss paint?
Matte has no sheen and hides imperfections best — ideal for ceilings and feature walls. Eggshell has a slight sheen and is washable — the standard for living rooms and bedrooms. Gloss is highly durable — used for woodwork, skirting and doors.