Paint Calculator

Paint Calculator estimates exactly how many litres of paint and which tin sizes you need for any UK painting project — built for tradespeople and DIYers.

Enter your room dimensions, pick a paint type, set surface condition and number of coats, and the app does the rest. Subtract door and window openings, apply waste allowance, and add a price-per-litre to see total cost in pounds.

KEY FEATURES

• 8 UK paint type presets — matt emulsion, silk emulsion, gloss, satinwood, eggshell, primer, masonry, ceiling paint
• Coverage rates matched to manufacturer TDS (Dulux Trade, Crown Trade, Johnstone's)
• Walls only, ceiling only, or walls + ceiling surface modes
• Surface condition: previously painted vs bare (with auto coverage adjustment)
• Masonry texture mode: smooth render vs textured pebbledash (drops coverage to ~5 m²/L per Dulux Weathershield TDS)
• Per-paint default coats (primer 1, finishes 2) — overridable
• Subtract openings (doors, windows) from gross wall area
• Waste allowance 0–25% (default 10%)
• Smart tin recommendation — compares single-tin vs greedy multi-tin and picks whichever wastes less paint (UK tin sizes: 750ml, 1L, 2.5L, 5L, 7.5L, 10L, 12L)
• Optional cost estimation with price-per-litre input
• Domain warnings — paint/surface mismatch, single-coat opacity, bare-needs-primer, exterior temperature limits (8–30 °C masonry), gloss-over-gloss adhesion
• Share results to text/email/messaging apps

CALCULATION ACCURACY

Coverage rates verified against Dulux Trade, Crown Trade, and Johnstone's technical datasheets. Tin sizes match B&Q, Homebase, and trade merchant SKUs. Bare-surface coverage uses a 30% reduction multiplier industry standard for new plaster, MDF, and timber.

WHO IT'S FOR

• Painters and decorators sizing up jobs
• Home renovators planning a room repaint
• Quantity surveyors estimating materials
• DIYers shopping at B&Q, Homebase, Wickes, or trade merchants

OFFLINE READY

Calculate without an internet connection. Results saved nowhere — all numbers stay on your device.

DISCLAIMER

This calculator is a planning tool. Always cross-check critical material orders with your paint supplier or a qualified decorator. Coverage rates vary with applicator (brush vs roller vs spray), surface profile, and colour change. For multi-paint jobs (e.g. masonry walls + ceiling paint), run separate calculations per paint type to avoid double-counting area.