Calculate how much paint you need for a wall or room, based on the area to be painted, number of coats, and the paint's coverage rate.
How to Use the Paint Calculator
Enter the "Wall Area (m²)" you plan to paint - use the Wall Area Calculator if you need to work this out from room dimensions.
Enter the "Number of Coats" you plan to apply.
Enter the paint's "Coverage (m² per liter)" per coat - check the paint can's label, as this varies by brand and surface.
Click "Calculate Paint Required" to see how many liters of paint you'll need.
How the Litres Are Worked Out
Paint required (litres) = Wall area (m²) × Number of coats ÷ Coverage (m² per litre). The coverage figure is for one coat, so a second coat simply doubles the area the paint has to cover. The result is the theoretical amount of paint that ends up on the wall; it does not add anything for spillage, rollers and trays, or a rough surface soaking up more than expected.
This calculator works in square metres. Many paint cans sold in India state coverage in square feet per litre instead. To convert, divide the square-feet figure by 10.764: a label that says 120 sq.ft per litre per coat is about 11.1 m² per litre.
Worked Example: One Bedroom
A bedroom measures 3.6 m × 3.0 m with a 3 m ceiling height. The four walls cover 2 × (3.6 + 3.0) × 3 = 39.6 m². Taking away a door of 2.1 × 0.9 m (1.89 m²) and a window of 1.2 × 1.2 m (1.44 m²) leaves 36.27 m². Add the ceiling, 3.6 × 3.0 = 10.8 m², for a total of 47.07 m².
With 2 coats and a coverage of 10 m² per litre, paint required = 47.07 × 2 ÷ 10 = 9.41 litres. A single 10-litre bucket would just cover it, with very little left for touch-ups. If the ceiling is being done in a separate ceiling white, run the walls and ceiling as two separate calculations.
Litres Needed for Two Coats
Area to paint
At 8 m²/L
At 10 m²/L
At 12 m²/L
20 m²
5.0 L
4.0 L
3.3 L
40 m²
10.0 L
8.0 L
6.7 L
60 m²
15.0 L
12.0 L
10.0 L
100 m²
25.0 L
20.0 L
16.7 L
150 m²
37.5 L
30.0 L
25.0 L
Lower coverage values suit rough, porous or exterior surfaces; higher values suit smooth, primed interior walls. Your paint's technical data sheet gives the figure to use.
Why Real Coverage Is Often Lower Than the Label
Surface texture: Label figures are measured on smooth, sealed surfaces. Rough plaster, textured finishes and exterior walls hold more paint.
Unprimed or new plaster: Bare cement plaster absorbs the first coat. Applying a primer, and putty where needed, gives a predictable base and stops the top coat being drunk into the wall.
Colour change: Covering a dark shade with a light one, or using deep, bright colours, may need a third coat. Enter 3 coats if you expect that.
Thinning: Paint thinned more than the manufacturer recommends seems to go further, but the dry film is thinner and usually needs an extra coat to look even.
Application method: Roller and brush application lose some paint to the tray and tools, and spray application can lose more as overspray.
Turning Litres Into Cans
Wall emulsions are commonly sold in 1, 4, 10 and 20 litre packs, though sizes vary by brand. A combination such as one 10-litre and one 1-litre pack is often cheaper per litre than several small ones. Buy all the paint for a room in one go, and if you do need more than one pack of a tinted shade, mix them together in a larger bucket before you start, so any slight colour difference between batches does not show on the wall.
Frequently Asked Questions
Paint Required (liters) = (Wall Area × Number of Coats) ÷ Coverage Per Liter. Each additional coat effectively multiplies the area you need to cover.
Coverage rate is usually printed on the paint can label, often expressed as sq.ft or sq.m per liter. It varies by paint type (emulsion, enamel, primer) and surface texture - rougher surfaces absorb more paint and reduce effective coverage.
It's a good idea to round up to the nearest available can size and keep a small surplus for touch-ups later, since matching the exact paint batch/shade later can be difficult.
Only if it is being painted with the same paint. Ceilings are usually done in a separate ceiling or white emulsion, so calculate the ceiling area (length × width of the room) on its own and enter it as a second calculation.
Two coats of finish paint over a primed surface is the usual practice for interiors and gives an even colour. Repainting in a similar shade over a sound surface may need only one, while a big colour change or a fresh, porous wall may need three.