Home & Lifestyle
Paint Calculator
Enter room wall dimensions, doors, windows, coats, and paint coverage to estimate litres of paint needed.
Inputs
Results
Useful next checks
- Check the inputs before relying on the result.
- Try a second scenario to compare outcomes.
- Read the guide below for context.
# Paint Calculator
Use this paint calculator to estimate how many litres of wall paint you need from room dimensions, doors, windows, coats, and the paint coverage rate.
What this calculator does
The calculator estimates paintable wall area, subtracts standard door and window allowances, multiplies by the number of coats, and adds an optional extra allowance for waste, touch-ups, or uneven coverage.
How it works
The wall area is estimated as `2 x (length + width) x height`. Doors are treated as 1.9 square metres each and windows as 1.5 square metres each. Litres needed are calculated as `total coat area / coverage per litre`, then increased by the extra allowance percentage.
Example calculation
For a 4 m by 3 m room with 2.4 m walls, one door, two windows, two coats, 10 square metres per litre coverage, and 10% allowance, the calculator estimates 6.31 litres of paint.
How to use the result
Round up to the nearest tin size and check the coverage printed on your chosen paint. Fresh plaster, bold colour changes, textured walls, and absorbent surfaces may need more paint.
Assumptions and limitations
This v1 tool estimates wall paint only. It does not include ceilings, skirting, trim, radiators, primer, or exact opening dimensions.
FAQs
Should I round up?
Yes. Paint is sold in fixed tin sizes, and a small surplus helps with touch-ups.
Does paint coverage vary?
Yes. Paint brand, surface texture, colour change, and application method can all change real coverage.
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Frequently asked questions
Does this include ceilings?
No. Version one estimates wall paint only. Add ceiling area manually by increasing the allowance if needed.
What opening sizes are assumed?
Each door is estimated at 1.9 square metres and each window at 1.5 square metres.