Measured wall area
Best for: Rooms where wall widths and height can be measured separately.
Main trade-off: Irregular rooms need each wall or section recorded.
Must check: Use paintable width × height and consistent metres.
How to choose
Paint quantity calculator
Estimate litres from measured area, coats and the exact product’s declared coverage.
Quick answer
What matters first
Measure the paintable area, subtract large openings only when useful, multiply by coat count, divide by the exact paint’s declared square metres per litre, then add a transparent contingency for texture and touch-ups.
Scope: Identify old coatings and suspect materials before disturbing them, then follow the current product instructions for the exact surface.
Four options to compare
Which input needs the most attention?
Openings and exclusions
Best for: Large doors, windows or fitted areas that materially reduce the paintable surface.
Main trade-off: Subtracting every small opening creates false precision.
Must check: Subtract only measured areas you genuinely will not coat.
Coats and product coverage
Best for: Using the exact tin or technical sheet rather than a generic average.
Main trade-off: Porous, textured or contrasting surfaces may achieve less than the declared ideal coverage.
Must check: Exact product, surface condition, primer and stated m²/litre.
Pack and contingency plan
Best for: Converting calculated litres into available pack sizes with some touch-up allowance.
Main trade-off: Too much contingency wastes paint; too little risks a batch mismatch.
Must check: Pack sizes, return terms, batch consistency and storage for touch-ups.
Interactive estimate
How many litres should I plan for?
Enter the combined width of the walls you will paint, the wall height and the exact coverage printed on your chosen product. The result keeps the base calculation and contingency separate.
Paintable area
25.8 m²
Base requirement
4.0 L
Plan to buy
4.4 L
Round to available pack sizes only after checking the exact tin, surface, primer, colour change and return terms. This estimate is not a coverage guarantee.
Use a transparent formula
Required litres = paintable square metres × coats ÷ declared square metres per litre. The calculator shows the base amount and the contingency separately.
- Paintable width and height
- Excluded opening area
- Number of coats
- Exact product coverage
- Chosen contingency
The estimate is not a product promise
Texture, porosity, colour change, application method and waste affect real use. Confirm the exact label and keep enough of the same batch for finishing and touch-ups.
What this guide cannot check
A buying guide cannot inspect your wall, wiring, material or installation.
Do not claim universal safety, guaranteed suitability, professional approval or permission to undertake protected work. Check current instructions, exact identifiers and local circumstances before acting.