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Anti-Mould Paint Calculator — How Much Anti-Mould Paint Do I Need?
Calculate anti-mould paint and fungicidal wash quantities for bathrooms, kitchens and damp-prone areas. Includes tin sizes and coverage for 2 coats.
Standard ceiling height is 2.4m
Average width per wall
Number of walls to paint
Ceilings in bathrooms and kitchens are often affected by mould
Longest dimension of the area
Shortest dimension of the area
Mould must be treated with fungicidal wash before painting
Average price per paint tin. The estimate uses one flat price per tin and excludes the fungicidal wash
Coverage per litre per coat (default 12 m²/L)
Number of anti-mould paint coats (default 2)
Conservative default 5 m²/L for thorough wetting — many products cover 10–15 m²/L, so check your label and raise this if it does
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How We Calculate This
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.
Frequently Asked Questions
Anti-mould paint contains fungicidal additives (biocides) that inhibit the growth of mould, mildew and algae on the painted surface. Most products use a combination of film-protecting biocides built into the paint film. The protection typically lasts 5-6 years. Anti-mould paint is not a cure for damp — it treats the symptom (mould growth) while you should also address the cause (condensation, ventilation, or moisture ingress).
Yes, always treat existing mould before applying anti-mould paint. First, apply a fungicidal wash (such as HG Mould Spray or Zinsser Mould Killer) and leave for the recommended time (usually 15-30 minutes). Scrub the area with a stiff brush, rinse, and allow to dry completely. If the mould has stained through, apply a stain-blocking primer before the anti-mould paint. Painting over existing mould without treatment will not stop it growing back.
Anti-mould paints vary by product: Zinsser Perma-White Interior Matt quotes around 10 m² per litre per coat, while Dulux Trade Mouldshield Fungicidal Matt quotes up to 17 m² per litre. A figure of 12 m² per litre is a sensible average for estimating, and this calculator defaults to it. Two coats are recommended for best protection. On porous or previously affected surfaces, coverage may be lower. Always check the manufacturer's technical data sheet for your specific product and adjust the coverage in the advanced options if needed.
Anti-mould paint is ideal for any room prone to condensation and moisture: bathrooms, en-suites, kitchens, utility rooms, basement rooms, and any walls or ceilings where mould has been a recurring problem. It can also be used in bedrooms where condensation occurs (for example, on cold external walls). Anti-mould paint is available in both brilliant white and a tintable base for coloured finishes.
Anti-mould paint helps, but you should also address the root cause. Ensure adequate ventilation — use extractor fans in bathrooms and kitchens (minimum 15 litres/second for bathrooms per Approved Document F). Maintain heating at a consistent level to prevent cold surfaces where condensation forms. Avoid drying clothes indoors without ventilation. Check for leaks, rising damp, or penetrating damp that may be contributing moisture. If the problem is persistent, consider a positive input ventilation (PIV) unit.
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Last updated: February 2026
Verified against UK standards · estimates only, confirm with your supplier.