How much paint do I need for the outside of a house?

The maths, step by step (UK example)

Take a 3-bed semi-detached house: footprint 8 m × 7 m, two storeys, walls 5 m high. The perimeter is 2 × (8 + 7) = 30 m, so the gross wall area is 30 × 5 = 150 m². Windows and doors are not painted: ten windows at about 1.5 m² each plus a front door at 2 m² remove 17 m², leaving 133 m² of paintable wall.

Two coats double the area to 266 m². Exterior masonry paint typically lists 6–10 m² per litre per coat, less than interior emulsion, because the paint is thicker and the surface is rougher. Using 7 m² per litre as a planning figure: 266 ÷ 7 = 38 litres. You cannot buy 38 litres exactly, so you buy 40 litres — four 10 L tins. If your render is rough, plan on 6 m² per litre instead and the same house takes 44 litres; if it is smooth and the can claims 10 m² per litre, 27 litres is enough. Always check the coverage printed on your own can — it beats any article's default, including this one.

The same house in imperial: 133 m² is about 1,430 sq ft of wall. Two coats is 2,860 sq ft. At a cautious exterior rate of 300 sq ft per gallon that is 9.5 gallons — buy 10. The calculator's default is 350 sq ft per gallon (the interior figure, from Sherwin-Williams guidance), so set the coverage yourself for exterior work: the field is editable on the tool page.

How much exterior paint for common house sizes

Two coats of masonry paint at 7 m² per litre, windows and doors deducted. These are planning figures for smooth-to-average render — roughcast, pebbledash and bare block take more.

If your house is not in the table, the paint calculator does the same maths with your exact wall area — measure the perimeter, multiply by the wall height, subtract the windows and doors, and let it work out the tins.

The US example: a two-storey home in gallons

A two-storey home with a 40 ft × 30 ft footprint and 18 ft walls has a perimeter of 140 ft, so the gross wall area is 140 × 18 = 2,520 sq ft. Twelve windows (15 sq ft each) and two doors (21 sq ft each) remove 222 sq ft, leaving 2,298 sq ft to paint. Two coats is 4,596 sq ft. At a cautious exterior rate of 300 sq ft per gallon that is 15.3 gallons — buy 16. At 350 sq ft per gallon it is 13.1 gallons, so 14 would do if your paint really covers that well on your siding. Buy the 16 and keep the spare gallon for touch-ups: exterior paint fades, and a matching tin two years later is worth more than the gallon cost.

Do not forget the gable ends, the primer and the trim

• Gable ends: a triangular gable adds ½ × width × height per end. An 8 m wide gable that is 2 m high adds 8 m² — two of them add 16 m², which is another 4.6 litres for two coats at 7 m² per litre. Pitched-roof houses need this; flat-roof houses do not.
• Primer: bare render, new blockwork and patched areas drink the first coat. One coat of exterior primer over the 3-bed semi's 133 m² takes 133 ÷ 7 = 19 litres — buy 20 litres. Skip primer on sound, previously painted masonry; two coats of topcoat are enough there.
• Trim, fascia and doors: these take a different paint (exterior wood or metal paint, usually gloss or satin) and are not part of the masonry figure. Allow roughly 5 litres (a gallon in the US) for the fascia, soffits and front door of a typical house, more if you have wooden window frames.
• Waste allowance: add about 10% for what stays in the tray, on the roller and in the brush, plus spills. For the 3-bed semi that lifts 38 litres to about 42 — so buy 45 litres (4 × 10 L + 1 × 5 L) if you want the safety margin, or 40 litres if you are happy to stretch the last tin.

When one coat is enough — and when it is not

• One coat can work for a same-colour refresh over sound, previously painted masonry with a good-quality exterior paint. The 3-bed semi then needs about 19 litres.
• Two coats is the default for a colour change, over patched render, over bare masonry, or where the old paint is chalking. One coat over any of those almost always shows through — and scaffolding or a ladder hire costs far more than the second coat of paint.
• Three coats is rare, but normal on very porous new render that was not primed, or when going from very dark to very white. Prime first instead: one coat of primer plus two coats of topcoat beats three coats of topcoat on bare render.

Painting inside as well? The interior maths is different — smoother walls, higher coverage — see how much paint a 12×12 room takes for the worked room-size table. And if the exterior work is part of a rental turnaround, the order of work matters: repainting a rental between tenancies covers the full void-period checklist.

Frequently asked questions