THE PAINT PLANNING GUIDE

From a wall size
to a shopping list.

A paint estimate has two parts: the quantity your measurements suggest, and the whole tins available to buy. Keep those numbers separate.

1. Count the surface, once

For each flat rectangular surface, multiply its width by its height. If four walls have the same dimensions, use a quantity of four. Add the surfaces, then subtract the area of doors, windows or sections you will leave unpainted.

A wall measuring 3 m by 2.4 m has an area of 7.2 m². A 0.9 m by 2 m doorway removes 1.8 m², leaving 5.4 m² to paint. Do not subtract that opening again for each coat: the coats are applied later.

2. Read the coverage per coat

The coverage input is square metres covered by one litre for one coat. Dulux’s official calculator explains the area ÷ coverage × coats formula and points readers to the product’s stated spread rate. Its guidance also notes that surface and product differences can affect requirements.

Coatcount starts with an illustrative 12 m²/L and two coats. Replace both with values appropriate to your actual paint. Primer, finish paint and a different ceiling product belong in separate plans.

Litres = net area × coats ÷ coverage

3. Add an allowance deliberately

The optional percentage is added after calculating paint volume. It is a planning choice, rather than a guarantee about waste. A 6 L estimate with a 10% allowance becomes 6.6 L. A zero allowance leaves the base estimate unchanged.

4. Round the purchase, not the measurements

Use the tin volume available from your supplier. Divide required litres by tin size and round upward to a whole tin. Coatcount uses one tin size per plan; it does not search combinations or compare different brands.

An arithmetic example

For 24 m², two coats and an entered coverage of 12 m²/L, the base estimate is 4 L. Adding 10% gives 4.4 L. With 4 L tins, buy two tins: 8 L purchased and 3.6 L above the estimate. With a 1 L tin entered instead, the order becomes five tins and 0.6 L surplus.

5. Compare the actual order cost

If you enter a tin quote, the cost is whole tins × quoted price, plus your delivery or transport amount. A missing price stays unknown. A quoted zero is treated as zero. Change the tin size and its matching quote together when comparing options.

Only combine surfaces using the same paint and colour. Openings are subtracted from walls; a checked ceiling is added separately. To plan a ceiling alone, remove every wall and opening row, then enter the ceiling’s dimensions.

Manufacturer reference checked 11 October 2026. This independent guide uses original examples and does not endorse a paint product.