Paint calculator (litres & tins)

Guessing paint quantities leads to leftover tins or mid-job trips to the merchants. Measure the room once, then let coverage and coats do the rest.

How it’s worked out

• Wall area = 2 × (length + width) × height − doors − windows
• Default door 1.6 m², window 1.2 m² (edit if yours differ)
• Optional ceiling area = length × width
• Litres = (total area × coats) ÷ coverage (m² per litre)
• Tins = litres ÷ tin size, rounded up

Worked example

Room 5 m × 4 m × 2.4 m, one door, one window, two coats at 12 m²/litre:

• Walls = 43.2 − 1.6 − 1.2 = 40.4 m²
• Litres = 40.4 × 2 ÷ 12 ≈ 6.73 L
• In 2.5 L tins → 3 tins

Frequently asked questions

How much paint do I need per square metre?

Many emulsions cover about 12 m² per litre per coat. Always check the tin — textured walls and darker colours often need more.

Should I paint the ceiling too?

Tick “include ceiling” to add floor area to the paint estimate. Ceiling paint is usually a separate product.