How much more paint does spraying use compared to brushing?

Spraying typically uses 30-50% more paint than brushing or rolling. HVLP sprayers are the most efficient at around 30% extra (1.3× factor), while airless sprayers use about 40% more (1.4× factor). This is due to overspray — tiny paint particles that miss the surface. Proper technique, correct tip size, and masking reduce waste significantly.

Do I need to thin paint for spraying?

Most paints need 5-10% thinning with water (for emulsion) or white spirit (for gloss/oil-based) when spraying. Check the manufacturer's data sheet for exact ratios. Some modern paints like Dulux Trade are 'spray-ready' and need no thinning. Over-thinning causes runs and poor coverage.

What is the difference between HVLP and airless sprayers?

HVLP (High Volume Low Pressure) sprayers are best for fine finish work — less overspray but slower. Airless sprayers pump paint at high pressure for fast coverage of large areas (walls, ceilings, exteriors) but produce more overspray. Air-assisted airless combines both benefits. For interior walls, airless is fastest; for trim work, HVLP gives the best finish.

How fast can you spray paint a room?

An experienced decorator can spray a typical room (walls and ceiling) in 20-40 minutes per coat, compared to 2-3 hours with a roller. However, masking and preparation for spraying takes 1-2 hours. Spraying is most efficient for large, open areas or multiple rooms. For a single small room, rolling may be quicker overall when you factor in setup time.

What spray tip size should I use?

For emulsion on walls, use a 517 or 519 tip (12-15 inch fan, 0.017-0.019 inch orifice). For trim/gloss, use a 310 or 312 tip (6 inch fan, smaller orifice). For primers and undercoats, a 517 works well. The first number doubled gives the fan width in inches; the last two digits are the orifice size in thousandths of an inch.

TradeCalculator

Spray Paint Calculator — Paint Volume for Spraying

Calculate how much paint you need when spraying, accounting for overspray, thinning ratio, and sprayer type.

Total Area to Spray

Combined surface area

Number of Coats

2 coats standard

Surface Type

Determines base coverage rate

Sprayer Type

Affects overspray amount

Thinning Ratio

Check paint data sheet

Price Per Litre (optional)

Include 5% equipment waste

Paint left in hoses, gun, and filters

How We Calculate This

This calculator determines how much paint you need when using a spray gun, which always requires more paint than brushing or rolling due to overspray and atomisation losses.

The formula

Brush equivalent = (Area × Coats) ÷ Coverage rate

Spray paint = Brush equivalent × Overspray factor

Total with thinner = Spray paint + (Spray paint × Thinning %)

For example, 50 m² with 2 coats at 10 m²/L = 10 L brush equivalent. With an airless sprayer (1.4×) = 14 L paint needed. With 10% thinning, total mixed volume = 15.4 L.

Overspray factors

HVLP: 1.3× — 65-70% transfer efficiency
Airless: 1.4× — 50-65% transfer efficiency
Air-Assisted Airless: 1.35× — 60-70% transfer efficiency

Frequently Asked Questions

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Last updated: March 2026

All calculations are estimates. Verify with your supplier.