Calculate exactly how much paint you need for one or more rooms, based on wall (and optional ceiling) dimensions, with deductions for doors and windows.
Room
Length (ft)
Width (ft)
Height (ft)
Doors
Windows
Ceiling?
Enter coverage according to your paint/product.
How to Use the Paint Quantity Calculator
Add each room with its length, width, and height, plus its door and window count. Tick "Ceiling?" to include the ceiling area for that room.
Set the door/window area used for deductions, your paint coverage rate, and the number of coats.
Click "Calculate" to see the paintable area and required paint for each room and in total.
What Happens for Each Room
Walls: 2 × (Length + Width) × Height, all in feet, giving the area of the four walls in sq.ft.
Ceiling: Length × Width, added only when "Ceiling?" is ticked for that room.
Deductions: number of doors × door area each, plus number of windows × window area each. The defaults of 21 sq.ft and 12 sq.ft correspond to a 3 × 7 ft door and a 4 × 3 ft window.
Paint: Paintable area × Coats ÷ Coverage (sq.ft per litre). Each room is shown separately and the totals are added at the end.
Worked Example: Two Rooms
The default room is 20 × 15 ft with 10 ft walls, 2 doors and 3 windows, ceiling not included. Walls = 2 × (20 + 15) × 10 = 700 sq.ft. Deductions = 2 × 21 + 3 × 12 = 78 sq.ft, leaving 622 sq.ft. At 2 coats and 100 sq.ft per litre, that needs 622 × 2 ÷ 100 = 12.44 litres.
Add a bedroom of 12 × 10 ft with 10 ft walls, 1 door, 1 window and the ceiling ticked. Walls = 440 sq.ft, ceiling = 120 sq.ft, minus 33 sq.ft for the openings = 527 sq.ft, which needs 10.54 litres. The two rooms together come to 1,149 sq.ft and 22.98 litres.
Ticking the ceiling in the first room would add 300 sq.ft and raise its paint to 18.44 litres, which shows how much a ceiling adds in a large room.
Planning a Whole-House Repaint
Rooms painted in the same shade can share one purchase. Add up the litres for those rooms from the per-room results, then buy for each shade separately.
Ceilings are usually done in white or a ceiling emulsion. If so, leave "Ceiling?" unticked and work out the ceilings in a separate calculation with that product's coverage.
If one room has an unusual door, such as a wide sliding door to a balcony, adjust the door count so the deduction is roughly right, for example count a 6 × 7 ft opening as two standard doors.
Built-in wardrobes, kitchen cabinets and tiled areas are not deducted automatically. Reduce the room height or length for those walls, or subtract the area by hand.
Round the total up to available pack sizes and keep the leftover, labelled with the shade code and room, for later touch-ups.
Choosing a Coverage Figure
The coverage box takes sq.ft per litre for one coat. Paint labels and shade cards in India often give this figure directly, sometimes as a range, for example for a smooth, primed wall. Use the lower end of the range for rough, previously unpainted or textured walls, and for deep colours that may need extra coats. Entering 100 is a cautious starting point when you do not have the label to hand, but the product's own figure will always be more accurate.
Frequently Asked Questions
Wall Area = 2 × (Length + Width) × Height — the perimeter of the room multiplied by wall height. Door and window areas are then subtracted to get the paintable area.
Coverage varies with paint type, the surface being painted, application method, number of coats, and manufacturer — there's no single fixed number. Check your paint tin's label for its stated coverage and enter that value here.
Yes. This calculator covers the finish paint only. New walls, repaired patches and walls with a big colour change usually need a coat of primer, and uneven walls may need putty first. Use the Primer Calculator and Putty Calculator with the same paintable area.
The room table and door and window areas are in feet and square feet. Convert metres to feet by multiplying by 3.281 before entering them, and make sure the coverage figure is also in sq.ft per litre.
The ceiling area equals the floor area, so in a 20 × 15 ft room it adds 300 sq.ft, nearly half as much again as the walls. Include it only if the ceiling is being painted with the same paint.