Calculate how much paint you need for walls, ceilings, or both. Works with emulsion, masonry paint, gloss and primer. Get litre counts, tin quantities and cost estimates.
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Create Your Free ProposalApproximate coverage rates and costs for common paint types used in the UK trade.
| Paint Type | Coverage (m²/L) | 2.5L Tin | 5L Tin |
|---|---|---|---|
| Matt Emulsion | 12 m²/L | £15 - £30 | £25 - £45 |
| Silk Emulsion | 12 m²/L | £18 - £35 | £28 - £50 |
| Masonry Paint | 8 m²/L | £20 - £35 | £30 - £55 |
| Gloss / Satinwood | 14 m²/L | £15 - £30 | £25 - £45 |
| Primer / Undercoat | 10 m²/L | £12 - £22 | £20 - £35 |
| Ceiling Paint (matt) | 12 m²/L | £15 - £28 | £24 - £42 |
Ordering the right amount of paint saves time, money and return trips to the merchant. This guide explains how professional painters estimate coverage and what factors affect your calculation.
For walls: Wall area = Perimeter x Height. The perimeter is calculated as 2 x (Length + Width). For ceilings: Ceiling area = Length x Width. Divide the total paintable area by the coverage rate of your paint (in m² per litre), then multiply by the number of coats.
A standard internal door opening is approximately 1.89m² (0.9m x 2.1m). A typical window is around 1.44m² (1.2m x 1.2m). Deducting these from the wall area gives a more accurate paint estimate and can save you buying an extra tin on smaller rooms.
Two coats is the standard for almost all painting work. Use one coat only for same-colour touch-ups where the existing surface is in good condition. Three coats may be necessary when:
Five-litre tins are typically 30-40% cheaper per litre than 2.5L tins. For any room where you need more than 3 litres, it is more economical to buy a 5L tin. Keep leftover paint for touch-ups -- store it in a cool, dry place with the lid firmly sealed.
When pricing a decorating job, include paint costs, preparation (filling, sanding, masking), labour time, and access equipment. Use tools like QuoteSmith to build professional proposals that clearly itemise materials and labour, helping you win more work and set clear expectations with customers.
Common questions about calculating paint quantities for decorating jobs.
Emulsion covers about 12m² per litre on smooth surfaces. Masonry paint covers around 8m² per litre. Gloss and satinwood cover approximately 14m² per litre. These rates vary based on surface porosity, texture, and how dramatic the colour change is.
Two coats is standard for most jobs. Use one coat only for same-colour touch-ups where the existing surface is in good condition. Use three coats when making a dramatic colour change (e.g., dark to light) or when painting on new plaster that has already had a mist coat.
2.5L tins are better for small rooms or when colour matching is critical. 5L tins are more economical, typically 30-40% cheaper per litre. For large areas like open-plan rooms or whole-house repaints, always buy 5L tins to save money.
Yes. New plaster must be sealed with a mist coat (emulsion diluted 70:30 with water) before applying full-strength paint. This does not need to be calculated separately -- just thin your first coat. Without a mist coat, the paint will flake and peel over time.
Use our calculator with the feature wall dimensions as a single wall. Enter the wall length and height, select "Walls only", and calculate. Consider using 3 coats for bold or dark feature wall colours, especially when covering a lighter base colour.
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