Free tool · Money
Paint Calculator
Estimate how much paint you need for a room.
Enter your room’s wall dimensions, number of walls, doors, and windows, along with your paint’s coverage rate and number of coats, to estimate how many liters of paint you’ll need. Saves guessing or over-buying before a painting project.
- Nothing leaves your device
- Runs entirely in your browser
- Free, no account needed
How to use Paint Calculator
Three steps, and nothing to install.
Measure your walls
Enter the dimensions and the number of walls.
Subtract doors and windows
Enter how many of each so their area is deducted.
Add coverage and coats
Take the coverage figure from the tin and choose your number of coats.
More free tools
Free, private, and no sign-up on any of them.
How this works in your browser
Total wall area is calculated from your dimensions and wall count, then standard allowances are deducted for each door and window, roughly 1.8 and 1.4 square metres respectively. Using fixed allowances rather than asking for every opening's measurements is a deliberate trade: it is close enough given that you should be rounding up to whole tins anyway, and it keeps the input manageable. That net area is divided by your paint's stated coverage and multiplied by the number of coats. The figure that most affects accuracy is the coverage rate, which is why it is an input rather than an assumption, since it varies considerably between paint types and surfaces.
Paint Calculator vs. typical online calculators
| Feature | Paint Calculator (in-browser) | Typical online calculators |
|---|---|---|
| Where the maths runs | In your browser, on your device | Often posted to a server to compute |
| Your inputs are stored | Never - nothing is sent or saved | Frequently logged with your session |
| Works offline once loaded | Yes | No - needs a live connection |
| Ads inside the result area | None | Common on free calculators |
| Account required | No | Often, to save or export results |
| Usage limits | None - free, unlimited use | Sometimes capped per day |
Who uses Paint Calculator
Planning a room repaint
Work out how many tins to buy before starting.
Budgeting a decorating job
Estimate paint cost across several rooms.
Avoiding a mid-job shortfall
Buy enough in one batch so the colour matches throughout.
Quoting work
Give a client a materials figure based on actual measurements.
Frequently asked questions
What it can and cannot do, and what happens to your files.
How are door and window deductions calculated?
Each door is assumed to take up about 1.8 square meters and each window about 1.4 square meters of wall area, subtracted from the total before calculating paint needed.
What does "coverage" mean?
Coverage is how many square meters one liter of your specific paint covers - check the paint can label, as this varies by brand and paint type.
Should I round up the result?
Yes, paint is typically sold in fixed can sizes, so round up to the nearest can size available and consider buying slightly extra for touch-ups.
Do I need to include the ceiling?
Not in this calculation, which covers walls only. Ceilings are measured as floor area, usually take a different paint, and often need an extra coat because they are lit from below. Work them out separately rather than adding them into the wall figure.
How many coats will I actually need?
Two is standard on a similar colour. Expect three when covering a dark colour with a light one, painting over a strong colour, or working on bare plaster, which drinks the first coat. Primer on bare or heavily patched surfaces saves a topcoat and gives a more even finish.
Why is my real coverage worse than the tin claims?
Because stated coverage assumes a smooth, sealed, previously painted surface. Textured wallpaper, bare plaster, render and anything porous absorb considerably more, sometimes half again. If the surface is rough or new, budget above the calculated figure.
Should I buy extra?
Yes, and buy it in the same batch. Colour can vary slightly between production batches, so a top-up bought months later may not match exactly. Keeping a sealed remainder from the original batch is what makes touch-ups invisible.
Estimate paint needed instantly - free.
Files never leave your device. No upload, no account, and free for unlimited use.