Paint Calculator
Litres of paint for the four walls and ceiling, and how many cans.
Recent
Formula
How the calculation works
The area is the four walls plus the ceiling. The walls are the perimeter -- twice the length plus twice the width -- times the height, and the ceiling is length times width. A second coat doubles the paint, not the wall: the litres are the area times the number of coats divided by ten, the planning figure for one litre per coat.
Because paint is sold in fixed cans, the litres to buy is rounded up to whole cans rather than left as a fraction. The room's wall area, ceiling area and the raw litres are all shown, so the sum can be checked and a painter's own figure compared line by line.
Common mistakes
- Measuring the floor and calling it the wall area. The walls are the perimeter times the height, which is usually far larger.
- Forgetting the ceiling, which is a fifth or more of the total on a normal room.
- Buying the exact litres and running short. An opened can of a different batch can be a shade off.
When to use it
- Use it to buy paint for a room, or to check a painter's estimate before agreeing a price.
- It is a planning figure. Rough or new walls drink more, so allow a little extra.
Worked example
5 × 4 m at 3 m high, two coats: 74 square metres, about 14.8 litres, or four 4-litre cans.
Common questions
Why are the doors and windows not deducted?
Because erring on the high side is safer with paint. Deducting them saves a little, but corners, frames and touching up spend it again -- and the frames get painted too.
Why 10 square metres per litre?
It is a planning figure. A rough or new wall drinks more paint and a smooth one less. Going from a dark colour to a light one can need three coats -- change the coat count when that applies.
Related tools
-
Discount Calculator
See what you actually pay after a discount, and how much you save.
-
Tip Calculator
Add a tip to the bill and split it between people.
-
Add Tax / VAT Calculator
Add tax or VAT to a price to get the total.
-
Percentage Calculator
Find what percentage one number is of another.
-
Percentage Change
How much a number rose or fell between two points.
-
Monthly Budget Split
Divide monthly income into needs, wants and savings.
-
Profit Margin & Markup
Profit, margin and markup from a cost and a selling price.
-
Original Price from a Sale
Work back from a discounted price and the discount rate to the original.