Paint quantity calculator
Estimate paint litres and whole cans for walls minus openings; 40 m² with 2 coats at 10 m²/L and 10 % waste needs 8.8 L.
- Runs in your browser
- No upload
- Instant result
Quantity estimate only. This does not approve structural safety, load capacity, drainage, fire resistance or building-code compliance. Verify the design and local requirements with a qualified professional. Purchase quantities round up to whole packs.
Assumptions & formula
Formula and assumptions
w = Waste allowance/100; L=(ΣLW−Σab)×coats/coverage×(1+w); N=ceil(L/pack)
The prefilled values are editable examples, not product specifications. Enter your supplier’s yield, density, coverage and packaging values, and add an allowance for overlaps, compaction and cuts where needed.
Purchase counts use the exact entered decimals and unit factors, without a rounding tolerance that could discard a real remainder. π and irrational square roots use enclosing bounds; ambiguous counts produce an error. Counts must be safe integers.
Results
Enter values and press Calculate to see the result here.
How to use this calculator
- Set inputs and units
Enter the wall rectangles minus the openings, the number of coats, the manufacturer’s coverage in m²/L and the liters per tin.
- Calculate
Check this worked example: (5×2+2×3−2×1) m²=14 m²; coats2,coverage10 m²/L,tin2.5 L,waste0% →2.8 L,2 tins
- Results
Multiply the area by the number of coats before you divide by the coverage. Whole tins add up to more than the exact liters needed.
Questions and limits
Does coverage already include two coats?
Use the supplier’s coverage per coat and enter the number of coats separately. Don't double-count a quoted multi-coat allowance.
Which input errors should I correct?
Use 1–20 whole coats, positive coverage and tin volume, and openings smaller than the gross wall area.
What does this calculation leave out?
No color matching, surface preparation, absorption, primer compatibility or guaranteed coverage in real conditions.