Paint Calculator

Area to paint, m²

Number of coats

Coverage, m² per litre

Tin size, l

Result

Paint in total, l8
Per coat, l4
Tins3
Litres purchased8.1
Primer, l4

Two coats is the norm, not a nicety

How much paint a given number of coats will take, how many tins that is, and how much primer to add.

Coverage is printed on the tin, usually between 8 and 14 square metres per litre. That figure is for one coat on a prepared surface, and taking it at face value is optimistic — rough plaster can push consumption up by half.

Two coats is nearly always right. One coat leaves streaks and lets the substrate show, particularly on a colour change. The exception is repainting the same shade on a smooth wall.

What this calculator shows

Total litres and litres per coat
How many tins to buy and how much paint that actually is
Primer separately — one coat is enough

What to keep in mind

Coverage comes from the tin; going from dark to light needs a third more, or a third coat.
Primer is estimated at one coat over the same area at the same coverage.

FAQs

How many coats does a wall need?

Two in the vast majority of cases. Three when going from dark to light, or with saturated reds and yellows, which cover worst of all.

Do I need primer?

Yes. It evens out absorbency and noticeably cuts paint consumption, often paying for itself. On plasterboard or fresh filler it is not optional.

Why is real consumption higher than the label says?

The label figure comes from a perfectly smooth surface with a short-pile roller. Textured plaster, a long pile and brush work add 20 to 50 percent.

Can I paint over old paint?

If it is sound and of the same type. Water-based over oil-based without primer will peel. Test a small patch with tape before committing.

Worked example

A room ready for painting

Input: 40 m², 2 coats, 10 m²/l coverage, 2.7 l tin

Output: 8 litres of paint, 3 tins

Note: Three tins give 8.1 litres — barely enough. On rough walls, buy four; the remainder is useful for touching up knocks.

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Paint Calculator

Result

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Wall Area Calculator

Wallpaper Calculator

Drywall Calculator

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