Free Paint Calculator – Estimate Litres of Paint

How to Work Out How Much Paint a Room Needs

Buying paint is a guessing game unless you measure first, and guessing wrong costs money in both directions — a half-finished wall on a Sunday evening, or three unopened tins in the storeroom. This calculator takes a room's length, width, and wall height, along with the number of coats and the paint's coverage rate, and returns the litres you need plus the total wall area. Weekend DIY painters, homeowners briefing a contractor, and landlords repainting between tenants all benefit from having the number before the shop visit rather than after. It also lets you check a painter's material quote instead of accepting it. The method is two steps. Wall area for a rectangular room is the perimeter times the height, which works out to 2 × (length + width) × height. Then litres = wall area × number of coats ÷ coverage. Coverage is printed on the tin and expressed as area per litre per coat; around 350 square feet per litre is typical for smooth interior emulsion, though rough plaster, textured finishes, and porous new walls can drop that to 250 or lower. Since paint sells in fixed can sizes, the result is rounded up. Note the calculation covers walls only and does not subtract doors and windows, which deliberately leaves a little spare for touch-ups. Here is a real room. A bedroom 12 feet by 10 feet with 10-foot walls has a perimeter of 2 × (12 + 10) = 44 feet, so the wall area is 44 × 10 = 440 square feet. For two coats at 350 square feet per litre, that is 440 × 2 ÷ 350 = 2.51 litres, so you buy 3 litres. Try a bigger space: a 15 by 13 foot living room with the same height gives 560 square feet and needs 3.20 litres for two coats, rounding to 4. If the walls are rough and coverage drops to 250, that first bedroom needs 3.52 litres instead — the same room, one extra tin, purely because of surface texture. The practical cases vary. Someone painting a dark accent wall over a pale one sets three coats and sees the bedroom requirement rise from 2.51 to 3.77 litres. A landlord repainting four identical flats multiplies one room's figure across the set and orders in bulk at a better rate per litre. A homeowner comparing a ₹420-per-litre premium emulsion against a cheaper option can price both jobs properly, since 13 litres at ₹420 is ₹5,460 and the coverage difference between grades often offsets the price gap. And anyone briefing a painter can check whether the quoted material quantity is reasonable or padded, which is a useful conversation to have before the work starts rather than after. Painters often quote material generously because leftover paint stays with them. A couple of honest limits. Ceilings are not included — measure the ceiling as length × width and treat it separately, since ceiling paint is often a different product. Primer is also excluded, and new plaster or a major colour change usually needs a coat of it, which is a separate purchase entirely. The mistake most first-timers make is trusting the coverage figure on the tin without adjusting for their walls: manufacturers quote it on smooth, sealed, primed surfaces under ideal conditions, and real walls routinely deliver 20 to 30 per cent less. When in doubt, use a lower coverage number and accept a little leftover paint, which is far cheaper than a second shop trip and the risk of a slightly different batch shade. Everything runs on your device, so your room details and budget stay completely private.

Paint Calculator Formula & Method

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