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Paint & Wallpaper Calculators

Primer Calculator

Primer or sealer needed before painting, adjusted for how porous the surface is.

Enter values

Results update as you type.

Result

Primer required

5 litres

On new plaster a mist coat is emulsion thinned 30% with water — it soaks in and seals the surface.

5 litre tins
1
2.5 litre tins
2
Coverage assumed
9 m²/L
Primer cost
$40.00

About the Primer Calculator

Primer or sealer needed before painting, adjusted for how porous the surface is.

Also known as: undercoat calculator, sealer quantity, how much primer, mist coat calculator.

How to use this calculator

  1. Enter area to prime, surface, coats, price per litre.
  2. The result updates instantly as you type — press Calculate (or Enter) at any time.
  3. Review the breakdown shown under the main result.
  4. Use Copy result or Share to save the answer or send a link with your inputs.

Formula

litres = area × coats ÷ coverage

Worked example

Using the values pre-filled in the calculator above:

  • Area to prime = 45 m²
  • Surface: New plaster (mist coat)
  • Coats = 1
  • Price per litre = 8

the calculator returns:

  • Primer required: 5 litres
  • 5 litre tins: 1
  • 2.5 litre tins: 2
  • Coverage assumed: 9 m²/L