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Paint Calculator

Everyday

Calculate exactly how much paint you need for any wall area. Enter the area, number of coats, and coverage rate to get litres required, rounded for purchase.

Reviewed by the thecalcu.com team · Last updated July 16, 2026

11,000
14
516

Paint Needed (rounded for purchase)

8
Exact Paint Needed
8

This calculator computes your Paint Needed (rounded for purchase), Exact Paint Needed from the values you enter.

Inputs
Wall AreaNumber of CoatsCoverage Rate
Outputs
Paint Needed (rounded for purchase)Exact Paint Needed

What is a Paint?

A Paint Calculator works out exactly how much paint you need to cover a given wall area, accounting for the number of coats you plan to apply and your paint's specific coverage rate. Buying paint without a clear estimate usually means either running short mid-project, a frustrating delay while matching the exact colour again, or over-buying and wasting money on unused tins.

This calculator converts your wall area, coat count, and coverage rate into a precise litre figure, then rounds up to a practical purchasing amount. It pairs well with the Square Footage Calculator for measuring the area in the first place, and the Tile Calculator for other surface-covering material estimates.

Why Use a Paint Calculator?

Estimating paint by eye or rough guesswork is one of the most common ways home painting projects go over budget or get delayed by an unplanned trip back to the store. Paint coverage rates aren't intuitive, a 40 m² room with two coats needs roughly double what a single-coat estimate would suggest, and that doubling is easy to forget when estimating informally.

This calculator removes the guesswork by applying the actual coverage maths automatically. Someone planning a full room repaint can enter their measured wall area once and immediately know how many litres to buy, with both an exact figure and a rounded purchasing target, the same practical approach the Concrete Calculator takes for estimating building material quantities.

Who Should Use This Calculator?

  • Homeowners planning a DIY paint job who want to buy the right amount of paint without over- or under-purchasing.
  • Painters and contractors quoting a job who need a quick material estimate based on wall area.
  • Renters preparing to repaint before moving out, who want to estimate cost and quantity before buying supplies.
  • Interior designers budgeting paint costs across multiple rooms or a full property.
  • Anyone comparing paint brands with different coverage rates to see how the choice affects total quantity needed.

What Insights Does the Paint Calculator Give You?

The calculator returns two related figures so you can both plan and purchase accurately:

  • Paint Needed (rounded for purchase), the practical amount to buy, rounded up to the nearest whole litre so you don't fall short.
  • Exact Paint Needed, the precise calculated amount, useful for cost estimation or comparing against a specific tin size.

Showing both figures means you can use the rounded number for shopping while still seeing the underlying precise calculation for budgeting purposes.

How to use this Paint calculator

  1. Measure your total Wall Area in square metres, add up all walls you're painting, minus any doors or windows you'll skip.
  2. Set the Number of Coats you plan to apply, most projects need at least 2 for even coverage.
  3. Check your paint can's label for its stated coverage rate and enter it as Coverage Rate, or use the default if unsure.
  4. Read the Paint Needed (rounded for purchase) result, this is the amount to buy.
  5. Check Exact Paint Needed if you want the precise figure for budgeting or comparing against specific tin sizes.
Show formula & methodology ↓Show less ↑

Formula & Methodology

The calculator multiplies wall area by the number of coats, then divides by the coverage rate:

Paint Needed (litres) = (Wall Area × Number of Coats) ÷ Coverage Rate

The result is then rounded up to the nearest whole litre for practical purchasing.

Worked example: for a 40 m² wall area, 2 coats, and a coverage rate of 10 m² per litre:
- Total area to cover = 40 × 2 = 80 m²
- Paint needed = 80 ÷ 10 = 8 litres (exact)
- Rounded for purchase: 8 litres

Frequently Asked Questions

How much paint do I need for a room?
The amount of paint you need depends on the total wall area, how many coats you're applying, and the coverage rate of your specific paint. As a rough guide, most emulsion paints cover around 10 square metres per litre per coat, so a 40 m² wall area with two coats needs roughly 8 litres.
How do I calculate wall area for painting?
Multiply each wall's width by its height and add the totals together, then subtract the area of any doors or windows you won't be painting over. For a quick estimate, many people simply measure the room's perimeter and multiply by the wall height.
Why does the number of coats matter so much for paint quantity?
Each additional coat requires covering the same area again, so paint needed scales directly with the number of coats, two coats need exactly double the paint of one coat for the same wall area. Most painted walls need at least two coats for even, opaque coverage, especially over a different existing colour.
What is a typical paint coverage rate?
Coverage varies by paint type and brand, but emulsion and wall paints commonly cover 8–12 square metres per litre per coat, while specialised paints (like high-gloss or textured finishes) may cover less. Check your specific paint can's label for the manufacturer's stated coverage rate for the most accurate result.
Why does the calculator round the result up?
Paint is sold in fixed container sizes, and running short mid-project to find an exact colour match again is far more inconvenient than buying slightly more than the exact calculated amount. Rounding up to the nearest litre gives a safer purchasing target while the exact figure is still shown for reference.
Should I buy extra paint beyond the calculated amount?
Many painters add a 10% buffer beyond the calculated amount to account for uneven surfaces, touch-ups, and minor spillage, especially for textured walls that absorb more paint than smooth ones. If your walls are rough or you're using a light colour over a dark one, consider rounding up further.
Does wall texture affect how much paint I need?
Yes, textured, rough, or porous surfaces absorb more paint than smooth, previously painted walls, sometimes requiring 10–20% more paint than the calculator's estimate. If you're painting over bare plaster or a textured finish, increase your coverage rate input accordingly.
What's the difference between this and the Tile Calculator?
The [Tile Calculator](/tile-calculator/) estimates how many tiles are needed to cover a floor or wall area, while this Paint Calculator estimates liquid paint volume for the same kind of area. Both work from a similar starting point, total surface area, but apply to entirely different materials.
How do I measure wall area if the room has multiple walls?
Calculate each wall's area separately (width × height) and add them together to get the total wall area, then enter that combined figure into the calculator. Subtract door and window areas from the total if you don't plan to paint over them.
Does this calculator work for exterior painting too?
Yes, the same area-and-coverage logic applies to exterior walls, though exterior paints often have different coverage rates than interior emulsion paints. Check your specific exterior paint's coverage rate on the can and adjust the Coverage Rate input accordingly.
Also known as
how much paint do I needpaint coverage calculatorwall paint calculatorlitres of paint neededpaint quantity estimator