HesapHanem

Paint Calculator

How much paint do I need?

How it is calculated

The tool works in three steps. First, the paintable surface is multiplied by the number of coats: total area = area × coats (m²). Second, that is divided by the coverage of the paint: liters = total area ÷ coverage, where coverage is in m² per liter. Third, the number of cans is cans = ceil(liters ÷ can size), rounded up to a whole can because shops do not sell fractions. Area, coats, coverage and can size must all be greater than zero, otherwise no result is shown. Doors, windows and other openings are not subtracted automatically, so enter the net area you actually intend to paint. Coverage differs by paint and surface, so use the figure on the tin; no allowance for waste or rough walls is added.

Worked example

A room has 45 m² of wall to paint with 2 coats. The paint covers 10 m² per liter and is sold in 2.5 L cans. Total area to cover: 45 × 2 = 90 m². Paint needed: 90 ÷ 10 = 9 liters. Cans: 9 ÷ 2.5 = 3.6, which rounds up to 4 cans. The tool shows 9.00 L needed, a total area of 90.00 m² and 4 cans, leaving about 1 liter spare.

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Common mistakes

  • Entering floor area instead of wall area. Walls are height × perimeter, not length × width of the room.
  • Forgetting that the coat count multiplies the area. Two coats need twice the paint of one.
  • Using the wrong coverage unit. The field is m² per liter; a tin that says per 2.5 L must be divided first.
  • Not subtracting large windows and doors from the area, which makes the estimate too high.
  • Buying exactly the liters shown. The can count is rounded up, but if the exact liters are close to a full can, add a margin for touch-ups.

About this calculator

This tool turns the wall area you are about to paint into a concrete shopping quantity: how many liters of paint and how many cans to buy, based on that area, the number of coats planned, the coverage rate a liter of that specific paint provides and the size of the cans it is sold in. Coverage varies a lot between paint types and finishes, so the calculator lets the actual coverage-per-liter figure (usually printed on the can) drive the result rather than assuming a fixed average.

It is used by homeowners and DIY painters before a trip to the hardware store, and by painting contractors quoting a job, since buying too little paint means a mismatched batch on a second trip, while buying too much wastes money on unused cans. Running the numbers before shopping also makes it easier to compare the total cost of different paint brands or finishes for the same room.

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Comments (1)

  • Editorial team

    Treat the coverage printed on the tin as a best case. New plaster, bare wood and other porous surfaces soak up much more paint, especially in the first coat, so test with a lower coverage figure than the label for them. Ceilings and walls often need different paints, so run them separately and add the cans for each. Which surface are you painting, and did the real consumption match what the label said?

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