Decorating & Walls calculator
Paint Calculator
Work out paint litres or gallons from surface area, coat count and the exact product coverage rate, with an optional extra allowance.
Work out paint litres or gallons from surface area, coat count and the exact product coverage rate, with an optional extra allowance. For a reliable estimate, measure the real project rather than relying on nominal room or product sizes. The input most worth checking is coverage rate, coats and absorbency. Coverage on the tin is normally based on a particular surface and application method. Strong colour changes, porous surfaces or textured finishes can increase the litres needed.
What you need to enter
The Paint Calculator uses the following project information to calculate the result.
- Area
- Number of coats
- Coverage per unit
- Extra allowance (%)
Calculator result
Required coating quantity, rounded buying quantity
How the Paint Calculator works
Core method: quantity = area × coats ÷ coverage × (1 + wastePct/100). On the Paint Calculator, this relationship is applied specifically to general paint coverage on measured surfaces. Compatible measurements are converted to a common internal unit before calculation, then the result is returned in the selected unit system. The main variable to verify is coverage rate, coats and absorbency.
Paint Calculator worked example
Paint Calculator example: For an illustrative paint job covering 42 m², using two coats at 10 m² per litre with a 10% allowance gives about 9.24 litres. In practice, you would compare that figure with the container sizes sold for the specific product rather than trying to buy exactly 9.24 litres. Before relying on that figure, check coverage rate, coats and absorbency; the final decision should also follow the actual product or project specification.
Important calculation assumptions
For general paint coverage on measured surfaces, coverage on the tin is normally based on a particular surface and application method. Strong colour changes, porous surfaces or textured finishes can increase the litres needed.
Frequently asked questions
How do I set up accurate inputs for the Paint Calculator?
Start with the real project rather than nominal dimensions. Measure the surface area that will actually be coated, then enter the number of coats and the coverage figure printed for the exact product. That gives the Paint Calculator the inputs it needs for general paint coverage on measured surfaces.
What if my assumption for coverage rate, coats and absorbency is wrong in the Paint Calculator?
The key uncertainty in the Paint Calculator concerns coverage rate, coats and absorbency. Coverage on the tin is normally based on a particular surface and application method. Strong colour changes, porous surfaces or textured finishes can increase the litres needed.
Should I order exactly the amount shown by the Paint Calculator?
For the Paint Calculator, after calculating, round the litres or gallons up to available tin sizes and keep some matching paint for touch-ups. If the job includes several surfaces with different porosity, calculate them separately where possible.