Anti-Mould Paint Calculator — How Much Anti-Mould Paint Do I Need?

This calculator estimates the quantity of anti-mould paint and fungicidal wash needed based on the area of walls and ceilings to be covered. It accounts for two coats of paint and recommends standard tin sizes.

The formula

Paint (litres) = Total area (m²) ÷ Coverage × Number of coats (defaults: 12 m²/L, 2 coats — both adjustable in advanced options)

Fungicidal wash (litres) = Total area (m²) ÷ Coverage (default: 5 m²/L — adjustable)

Coverage rates

• Anti-mould paint: default 12 m² per litre per coat — within the typical 10–17 m²/L range for products such as Zinsser Perma-White (10 m²/L) and Dulux Trade Mouldshield (up to 17 m²/L). 2 coats recommended.
• Fungicidal wash: default 5 m² per litre per application. This is a deliberately conservative rule of thumb to ensure affected areas are wetted thoroughly — many ready-to-use products (e.g. Zinsser Mould Killer & Remover) state up to 15 m²/L and diluted treatments around 10 m²/L, so check your product label and raise the coverage in advanced options if your product goes further.

Standard tin sizes

• Anti-mould paint: packed into 2.5L and 5L tins (the common trade sizes — some products such as Zinsser Perma-White are also sold in 1L and 10L)
• Fungicidal wash: packed into 1L and 5L containers

The optional cost estimate multiplies a single tin price by the number of paint tins. It assumes one uniform tin price and does not include the fungicidal wash, so treat it as a rough guide rather than an exact quote — confirm prices per tin size with your supplier.

Preparation

If existing mould is present, it must be treated with a fungicidal wash first. Apply the wash, leave for the recommended time, scrub with a stiff brush, rinse, and allow to dry completely (usually 24 hours). Apply a stain-blocking primer if mould staining remains, then apply two coats of anti-mould paint allowing full drying time between coats.

Standards

Painting of buildings should comply with BS 6150 (Painting of buildings). Ventilation to prevent condensation and mould should comply with Approved Document F (Ventilation) of the Building Regulations.