Should I include doors and windows?

Subtracting their area gives a more realistic paintable wall area.

Why include an allowance?

A small allowance helps cover waste, touch-ups and variation in surface absorbency.

Does every paint cover the same area?

No. Use the coverage figure printed by the paint manufacturer.

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Paint Calculator

Estimate paint needed for walls and rooms.

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Perimeter (m)

Height (m)

Openings (m²)

Coats

Coverage (m²/L)

Estimate

Enter your values.

How to use the Paint Calculator

Enter the room or wall dimensions, coverage information and number of coats. UsefulFox estimates the paint required so you can plan the job before buying tins.

Paint calculation example

A room with several large walls may need more paint than expected once a second coat is included. Estimating coverage first helps reduce both shortages and unnecessary leftover paint.

What can a paint calculator be used for?

Use it when decorating bedrooms, living rooms, hallways, offices, feature walls or other interior spaces.

Measure before buying paint

Our complete paint quantity guide explains wall area, doors and windows, coats, manufacturer coverage and a worked room example.

Frequently asked questions

1Why does the number of coats matter?

Each additional coat increases the amount of paint required.

2Should I allow extra paint?

A small allowance can be useful for touch-ups, uneven surfaces and application losses.

3Does every paint have the same coverage?

No. Coverage varies by product, surface and application method, so use the manufacturer’s stated coverage where possible.

4Should I subtract doors and windows?

For a more precise estimate, subtract large areas that will not be painted.

Paint Calculator Guide

Work out paint quantities with a little more confidence. The calculator above does the arithmetic; these checks help you feed it better measurements and interpret the result sensibly.

How to get a better estimate

Measure the surfaces you actually plan to paint. For walls, multiply width by height and add the wall areas together.

Allow for the number of coats. Two coats uses roughly twice the paintable coverage of one coat.

Use the coverage figure on your chosen tin wherever possible. Different products and surfaces can cover differently.

Quick example

A 4 m × 3 m wall has an area of 12 m². If it needs two coats, you are effectively covering 24 m² before allowing for doors, windows or the specific paint coverage.

Before you buy

Use the result as a planning estimate, then check the dimensions, coverage, pack size and instructions for the actual product you intend to use. Round purchasing quantities appropriately rather than assuming a calculated fraction can be bought.

Common questions

Should I subtract doors and windows?

For a closer estimate, yes—especially where openings are large. For small openings, leaving them in can also provide a modest contingency.

Why can the real amount differ?

Surface porosity, colour changes, application method and the product itself can all affect coverage. Treat the calculator as a planning estimate and check the tin.

UsefulFox provides estimates for planning and comparison. Actual material requirements can vary with the product, surface, layout, installation method and site conditions.