Paint Calculator — Litres & Coverage
Calculate how much paint you need based on wall area, number of coats and paint coverage rate.
By Konstantin Iakovlev · Founder, Calks.uk
Last updated: · Verified against HMRC and GOV.UK 2026/27 rates
Paint Needed
5.8L
2.5L Tins
3
5L Tins
2
Wall Area
34.8 m²
Disclaimer
This calculator is provided for informational purposes only and should not be considered as financial or tax advice. All calculations are performed locally in your browser — no personal data is collected or sent to our servers. Rates and thresholds are sourced from HMRC and GOV.UK and are updated for the current tax year. Always verify results with HMRC or consult a qualified professional before making financial decisions.
How It Works
Paint coverage depends on the product type and surface texture. Emulsion paint for walls typically covers 10–12 m² per litre on smooth plaster. Gloss and satin for woodwork cover 12–16 m² per litre. Textured, bare or porous surfaces may require 20–30% more paint due to increased absorption on the first coat.
This calculator measures each wall (height × width), subtracts doors and windows, then divides the total area by the coverage rate. Two coats are standard for a colour change; a single coat may suffice for maintenance. The calculator adjusts for your chosen number of coats.
Enter room dimensions, number of doors and windows, and choose the paint type and number of coats. The calculator shows total litres needed and suggests tin sizes (most UK paints come in 2.5 L and 5 L tins). Buying the next size up is usually more economical than buying an extra small tin.
How much paint do you need? Standard coverage: 1 litre covers 11-13 m² with one coat on a sealed surface. Two coats recommended for colour change or new plaster — divide coverage by 2. Sample calculation: 4m × 3m room with 2.4m ceiling = wall area 33.6 m² (subtract 1.8 m² per door, 1.5 m² per window). 30 m² walls × 2 coats = 60 m² ÷ 12 m²/L = 5 litres of paint. Always buy 10-15% extra for touch-ups.
Paint types and where to use them. Matt emulsion: walls in living rooms, bedrooms — hides imperfections, no sheen. Silk/satin: kitchens, bathrooms, high-traffic — more washable, slight sheen. Eggshell: woodwork, doors, skirting (UK alternative to silk). Gloss: high durability for trim, but yellows over time — modern water-based 'eggshell' or 'satinwood' preferred. Specialist: anti-mould (bathrooms), masonry (exteriors — Dulux Weathershield 15-year guarantee), heat-resistant (radiators).
UK paint brands and price comparison. Budget: Wickes/B&Q own brand £15-£25/2.5L. Mid: Dulux £25-£40/2.5L. Premium: Farrow & Ball £67-£86/2.5L, Little Greene £55-£75. Trade: Dulux Trade Vinyl Matt £35/5L (5L lasts much further than 2×2.5L retail). Coverage difference: cheap paint often needs 3 coats; premium paint covers in 1-2. Test pots: £5-£8 — always buy before committing to £200+ paint for a room.
Preparation is half the job. Wash walls with sugar soap to remove grease and dust. Fill cracks with Polyfilla (small) or skim-coat large areas. Sand smooth (P120 grit then P180 finish). Mist coat new plaster: dilute paint 50/50 with water for first coat — seals porous surface. Mask edges with FrogTape or similar low-tack. Drop sheets to protect floor. Tools: 9-inch microfibre roller for walls, 2-inch brush for cutting in, paint kettle for dipping.
Cost of painting a UK home. Materials only (DIY): 3-bed semi interior = £200-£400 (8-12 litres premium paint, brushes, rollers, masking tape, drop sheets). Hiring a decorator: £150-£300/day, typical 3-bed full interior 5-7 days = £750-£2,100. Exterior masonry repaint £1,500-£3,500 for typical UK home. Always confirm prep work included in quote — drying time between coats is 4-6 hours emulsion, 16+ hours oil-based.
Example: Room 4 m × 3.5 m, 2.4 m ceiling, 1 door, 1 window, 2 coats emulsion
- Wall area: 2 × (4 + 3.5) × 2.4 = 36 m²
- Less door (1.8 m²) and window (1.5 m²): 32.7 m²
- Two coats: 32.7 × 2 = 65.4 m²
- Litres needed: 65.4 ÷ 11 = 5.9 L — buy 2 × 2.5 L or 1 × 5 L + 1 × 2.5 L
Frequently Asked Questions
- What does the Paint Calculator — Litres & Coverage do?
- Calculate how much paint you need based on wall area, number of coats and paint coverage rate.
- How much paint do I need?
- Wall area: (length × height each wall) − doors/windows. Coverage: emulsion 10-12 m²/litre, gloss/eggshell 12-14, masonry 5-7. For 2 coats: double the litres. Standard 4m × 4m × 2.4m room (~38m² walls minus door): 6-8 litres for 2 coats. Buy 10-15% extra for touch-ups.
- Primer vs no primer.
- Use primer when: painting over dark with light, bare wood/metal/plaster, glossy surfaces, water-damaged areas (stain-blocking primer), heavily patched walls. Skip primer for: same colour family, walls in good condition with similar finish, modern self-priming paints. Stain block primers £15-£30/litre but save 1-2 paint coats.
- Trade vs retail paint.
- Trade paints (Dulux Trade, Crown Trade, Johnstone's Trade): more per litre but better coverage — often 1 coat instead of 2. Retail (Wilko, B&Q): cheaper but lower coverage. Per-square-metre cost similar, but trade saves time. Trade also offered at Wickes Pro, Toolstation, Brewers. For full repaints, trade quality worth extra cost.