Paint Quantity Calculator
Litres or gallons of paint for walls and ceiling, with coats and wastage. Results update as you type.
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About the Paint Quantity Calculator
Find out how much paint to buy for a room from its length, width and height. Subtract doors and windows, choose one or more coats, add a wastage allowance, and optionally include the ceiling. Enter a tin size to see how many tins to buy and what you will have left.
It works in metric (metres and litres) or imperial (feet and US gallons).
Choose your currency (₹, $, €, £ and more) and every amount updates. The calculation runs in your browser, so the numbers you enter are not uploaded.
Paint Quantity Calculator example
Room length: 5
Room width: 4
Wall height: 2.7
Doors: 1
Windows: 2
Coats: 2
Wastage allowance: 10 %
Coverage per litre / gallon: 10
Tin size: 4
Price per litre / gallon: 450Paint to buy: 9.7 litres
Tins needed: 3 × 4 litres
Paintable area: 43.9 m²
Wall area: 48.6 m²
Doors and windows deducted: 4.7 m²
Paint before wastage: 8.8 litresHow it is calculated
The wall area is the room perimeter times the height. Doors and windows are deducted, and the ceiling (length × width) is added if you choose to paint it. The paintable area is multiplied by the number of coats, divided by the coverage printed on the tin, and increased by the wastage allowance.
The defaults are 2 coats, 10% wastage, 10 m² per litre (or 350 ft² per gallon), 1.9 m² per door and 1.4 m² per window.
Walls = 2 × (length + width) × heightPaintable area = walls (+ length × width for the ceiling) − doors − windowsPaint = paintable area × coats ÷ coverage × (1 + wastage)Tins = paint ÷ tin size, rounded up
What to enter
- Coats. Blank = 2 coats.
- Wastage allowance. Blank = 10%.
- Coverage per litre / gallon. From the tin. Blank = 10 m²/L (metric) or 350 ft²/gal (imperial).
- Tin size. Litres or gallons. Rounds up to whole tins.
- Area per door. Blank = 1.9 m² or 20 ft².
- Area per window. Blank = 1.4 m² or 15 ft².
Assumptions and limits
Coverage varies by brand, finish and surface, so use the figure on your tin. Primer is not included.
How to use the Paint Quantity Calculator
- Fill in the fields above. Required fields are marked, optional ones can be left blank and fall back to the defaults described on this page.
- Use “Try an example” to see a worked case, then replace the numbers with your own.
- Read the results as you type. The large card is the main answer and the smaller cards are the related figures.
- Copy a single value or everything, or share a link that keeps your inputs.
Paint Quantity Calculator FAQ
How does the paint quantity calculator work?
The wall area is the room perimeter times the height. Doors and windows are deducted, and the ceiling (length × width) is added if you choose to paint it. The paintable area is multiplied by the number of coats, divided by the coverage printed on the tin, and increased by the wastage allowance. The defaults are 2 coats, 10% wastage, 10 m² per litre (or 350 ft² per gallon), 1.9 m² per door and 1.4 m² per window.
How much paint covers a room of 5 m × 4 m?
With a 2.7 m ceiling, one door, two windows and two coats, the example above needs about 9.7 litres, so three 4-litre tins. Your own numbers will change this.
Why add wastage?
Rollers and trays soak up paint, rough walls drink more, and you will want some for touch-ups. 10% is a common allowance; use more for dark-to-light changes or porous walls.
Is this paint quantity calculator free and private?
Yes. It is free with no sign-up, and the calculation happens on your device, so your numbers are never sent to a server.
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