Free paint calculator: how much paint do you need to buy?
Measure each wall, add it to the list, and we'll total your surface area and tell you exactly how much paint to buy — so you finish the job without a second trip or a shelf of half-empty cans.
Paint Estimator
Tip: for a wall, enter its length × ceiling height. Add one line per wall as you measure around the room.
From tape measure to paint can in three steps.
Measure each wall
Pick your units, then enter each wall's length and height. Area fills in automatically as you type.
Add up the room
Hit "Add another surface" for every wall. The running total at the bottom keeps a live sum of your whole space.
Buy the right amount
Choose how many coats and we convert your area into gallons or litres — rounded up so you never run short.
How to estimate paint from surface area
Paint coverage is really just division. Every can tells you roughly how much area it covers, so once you know your total surface area and how many coats you want, the math is simple: area × coats ÷ coverage = paint needed. The hard part is measuring accurately and not forgetting a wall — which is exactly what the calculator above is for.
Measuring your walls
For each wall, multiply its length by the ceiling height to get its area, and add one line per wall. A standard room has four walls, but bump-outs, hallways, and stairwells add more — keep adding surfaces until you've gone all the way around. Working in a whole room? Measure the perimeter, multiply by the height, and you've got the total in one line if you prefer.
A realistic coverage rule
- Imperial: one US gallon covers roughly 350 sq ft per coat on smooth, primed walls.
- Metric: one litre covers roughly 10 m² per coat.
- Texture & color: rough or porous surfaces drink more paint, and a big color change usually needs two coats minimum.
We don't subtract for doors and windows on purpose — that small buffer covers cutting in, touch-ups, and the inevitable spill. It's better to have a little left for future scuffs than to run out two-thirds of the way down the last wall.
Don't forget the extras
Your wall paint is the big number, but a full job often needs a separate primer (especially over bare patches or dark colors) and trim/ceiling paint in a different finish. Price those alongside your budget — our Interior Design guide covers how color and finish choices change the feel of a room, and the Design Budget Calculator helps you split a room refresh sensibly.
Painting is the highest-impact, lowest-cost change in design — which is exactly why it's the first thing we recommend for both renters and owners looking to get more from their space.