Free calculator
Paint calculator
Enter your room size, the doors and windows, the number of coats and the coverage from the paint label. You get the litres and 3.78 L cans needed for the walls and the ceiling, counted separately.
Paint calculator
Calculated on lokalmatch.com
Your results
Walls
2 × 3.78 L
6.7 L of paint
Ceiling
1 × 3.78 L
2.7 L of paint
- Total paint
- 9.4L
- Wall area to paint
- 352sq ft
- Ceiling area
- 143sq ft
Litres are rounded up to whole 3.78 L cans. For a small job, a smaller can may be enough.
Estimates for planning only. Confirm quantities with your supplier or contractor before you order.
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How to measure for the paint calculator
- Measure the length and width of the room at floor level, wall to wall.
- Measure the wall height from the floor to the ceiling.
- Count the doors and windows. If they are much larger or smaller than the defaults, measure one and enter its area (width × height).
- Find the coverage on the can or the product data sheet. If it is given per 3.78 L can, divide it by 3.78 to get m² per litre, or switch to imperial and enter the square feet per can.
Assumptions behind the paint calculator
Every default below appears in the calculator and can be changed.
- Wall area = 2 × (length + width) × height, minus doors and windows. Ceiling area = length × width.
- Default door: 20 sq ft (1.86 m²), the area of a 36 × 80 in door. Default window: 12 sq ft (1.11 m²), a 3 × 4 ft window.
- Default coverage: 9.8 m² per litre, or 400 sq ft per 3.78 L can in imperial. That matches the 37 m² (400 sq ft) per 3.78 L Sico lists for its ceiling paint. Other products differ: Sico lists 49 to 55 m² per 3.78 L for its Evolution interior paint as a finish coat.
- Default: 2 coats. Each coat uses the full quantity again.
- Litres are rounded up to whole 3.78 L cans, separately for walls and ceiling, since ceilings are often painted with a different product. Primer, trim and doors are not included.
Paint calculator: tips before you buy
- Porous or unpainted surfaces absorb more paint. Sico’s Evolution data sheet, for example, gives a lower coverage for porous surfaces than for a finish coat.
- If you need several cans of a tinted colour, mix them together in a larger pail before you start so the colour is uniform.
- Label leftover paint with the room and the colour for touch-ups.
- Measure trim, doors and cabinets separately and use a product made for them.
Paint calculator: frequently asked questions
How much does a gallon of paint cover?
It depends on the product and the surface. In Canada, a “gallon” can holds 3.78 L. Sico lists about 37 m² (400 sq ft) per 3.78 L for its ceiling paint, and 49 to 55 m² (520 to 590 sq ft) for its Evolution interior paint as a finish coat. Use the figure on your own label.
Should I subtract doors and windows?
Yes. They aren’t painted with the wall colour, so the calculator removes them using the counts and sizes you enter. Set the counts to 0 to keep them in.
How many coats do I need?
Follow the label of your paint. The calculator multiplies the quantity by the number of coats you enter, so two coats take twice the paint of one.
Why are walls and ceiling calculated separately?
Ceilings are often painted with a different product and colour, so you buy the paint separately. The total line adds both.
Sources for the paint calculator
We checked these references on September 10, 2026. Product figures vary, so read the label or data sheet of the product you choose.
Last reviewed September 10, 2026
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