Paint Calculator
This paint calculator works out how much paint you need for a room or wall. Enter the area, coverage, and coats and the paint calculator tells you the paint to buy, answering how much paint do I need. It doubles as a paint coverage calculator and works from square feet or square meters.
Results
The Paint Calculator is part of our Floor & Wall collection. Browse more floor & wall to size, convert, and check your work alongside this tool.
What the paint calculator does
The paint calculator answers the question every decorator asks: how much paint do I need? Running out halfway through a wall leaves a visible join, and a fresh tin rarely matches, so this paint coverage calculator sizes the job up front from the area, how far the paint stretches, and the number of coats. It works as a wall paint calculator and a ceiling paint calculator alike.
Paint coverage formula
The paint calculator uses a direct calculation: area over coverage, times the coats.
Coverage is the figure on the tin, the paint coverage per litre or per gallon, and it drops on rough or thirsty surfaces, so trust the lower end of any range when you estimate how much paint you need.
Paint calculator example
Fifty square meters, paint covering 10 m² a liter, two coats, through the paint coverage calculator:
As a paint calculator square feet example, 540 sq ft at 350 sq ft per gallon over two coats needs about 3 gallons.
How to use the paint calculator
Enter the total surface area, the coverage the tin claims per liter or per gallon, and the number of coats. The paint calculator returns the paint to buy. It works from square feet or square meters, so it serves as a paint calculator square feet tool and a paint estimator by square footage.
Reading the paint calculator result
Round up to whole tins and keep a little spare for touch-ups from the same batch. Bare plaster, new wood, and strong colour changes drink more than the tin promises, so if you are covering any of those, the paint estimator by square footage should plan for an extra coat rather than hoping two will do.
When to use the paint calculator
- Working out how much paint do I need for a room
- Estimating with the wall paint calculator or ceiling paint calculator
- Costing a job with the paint coverage estimator
- Planning by area with the paint calculator square feet
Common paint calculation mistakes
- Trusting tin coverage on rough surfaces. Porous and textured walls need far more paint.
- Planning too few coats. Bare or dark surfaces often want a primer plus two coats.
- Buying exact. Round up and keep spare from the same batch for touch-ups.
Tips for accurate paint results
- Use the low end of the coverage range for anything rough or bare.
- Prime first over new plaster, wood, or big colour changes.
- Use the paint calculator square feet mode when your tin lists gallons.
Why coverage decides how much paint you need
Coverage is the number that makes or breaks the paint calculator estimate, and it is the one most people take on faith. The figure printed on the tin is measured on a smooth, sealed surface under ideal conditions, and real walls are rarely that. Fresh plaster pulls paint into its pores, textured render hides extra surface area in every bump, and bare timber drinks the first coat almost whole. On any of these the paint coverage per litre falls well below the label, so reading it literally is the fastest way to come up short.
Coats and the paint calculator
The coats matter as much as the coverage, and they interact. The first coat on a bare or strongly coloured surface does most of its work sealing and blocking rather than giving the final colour, which is why professionals prime first and treat the two topcoats as the real finish. When you plan with the paint calculator, think in terms of the surface underneath: a repaint in a similar shade might need only two coats at full coverage, while a bare or dramatic job needs a primer and two more, and the paint estimator by square footage changes accordingly.
Paint coverage chart
Typical coverage the paint calculator assumes by surface:
| Surface | Coverage per liter |
|---|---|
| Smooth plaster | 10–12 m² |
| Rough render | 6–8 m² |
| Bare wood | 8–10 m² |
Paint Calculator FAQ
How much paint do I need?
Divide the area by the coverage per liter, then multiply by the coats. The paint calculator does this: 50 m² at 10 m² per liter over two coats needs 10 liters.
How do I use the paint calculator in square feet?
Enter the area in square feet and the coverage per gallon (often 350–400 sq ft). The paint calculator square feet mode returns gallons, working as a paint estimator by square footage.
Why does coverage vary so much?
Rough and porous surfaces soak up paint, cutting the paint coverage per litre. Trust the lower number in any range for render, bare plaster, or new wood.
How many coats do I need?
Two is standard over a similar colour. Bare surfaces or big colour changes often need a primer plus two coats, so the paint coverage calculator should plan for three layers.