Paint Coverage Calculator
Estimate how much paint you need to cover a room's walls (and optionally ceiling) — accounting for door/window deductions, number of coats and a waste allowance — in liters or gallons, plus how many cans to buy.
Input
Metric enters dimensions in metres and paint in liters; imperial uses feet and gallons.
Room length (metres in metric, feet in imperial).
Room width (metres in metric, feet in imperial).
Wall height / ceiling height (metres in metric, feet in imperial).
Standard door deduction: 1.8 m² (about 20 sq ft) each.
Standard window deduction: 1.44 m² (about 15 sq ft) each.
Pick a typical coverage rate for this finish, or choose Custom to enter your own.
Number of coats to apply.
Volume of one can — liters in metric (default 5 L), gallons in imperial (default 1 gal).
Extra paint for spills, touch-ups and dry absorption.
Output
| Metric | Value |
|---|---|
| No data yet | |
One-line overview of net area, coats, paint needed and cans to buy.
Guides
The Paint Coverage Calculator estimates how much paint you need to cover a room's walls — and, if you choose, its ceiling — before you go shopping. Enter your room dimensions, the doors and windows to deduct, the finish you're using, the number of coats and a waste allowance, and it works out the paintable area, the liters or gallons required, and how many cans to buy. It supports metric (meters, liters) and imperial (feet, gallons) units.
How to use it
- Pick your unit system — metric (room in meters, paint in liters) or imperial (room in feet, paint in gallons).
- Enter the room length, width and ceiling height. Tick include ceiling if you're painting it too.
- Set the number of doors and windows to subtract from the paintable area — each uses a standard deduction (1.8 m² per door, 1.44 m² per window, roughly 20 and 15 sq ft).
- Choose a finish (matte, eggshell, satin, semi-gloss, gloss or primer) for a typical coverage rate, or select Custom coverage rate to enter your own figure from the paint can's label.
- Set the number of coats, a can size, and a waste factor for spills, touch-ups and absorption into new drywall.
Results update instantly. The table shows total wall area, ceiling area, door/window deductions, net paintable area, the coated area after multiplying by coats, the waste-adjusted area, total paint required, and the number of cans to buy (rounded up, since you can't purchase a partial can). A one-line summary is provided for quick copying.
What coverage rate should I use?
Coverage varies by finish and surface texture. This calculator's presets range from about 8 m²/L (330 sq ft/gal) for gloss to 12 m²/L (490 sq ft/gal) for matte — flatter finishes spread further because they don't need to level as smoothly. A widely used rule of thumb for a single coat on primed drywall is roughly 350 sq ft per gallon (about 8.6 m²/L); check the actual coverage rate printed on your paint can and use Custom coverage rate for the most accurate estimate, since it varies by brand and formulation.
How are doors and windows subtracted?
Each door subtracts a standard 1.8 m² (about 20 sq ft), and each window subtracts 1.44 m² (about 15 sq ft), from the gross wall (and ceiling, if included) area before the coats and waste calculations are applied. These are typical residential door/window sizes; for unusually large openings, reduce the door or window count and let the extra area count toward paintable wall space instead.
How does the number of coats affect the total?
The net paintable area (after deductions) is multiplied directly by the number of coats — two coats need twice the paint of one. Most projects need two coats for full color coverage and hide, especially over a different existing color; a single coat may suffice for touch-ups or when using a paint-and-primer-in-one on a similar base color.
Why does it round up to whole cans?
Paint isn't sold by the exact liter or gallon — you buy whole cans. The calculator divides the total paint volume (including your waste factor) by the can size and rounds up, so the "cans to buy" figure reflects what you'd actually purchase at the store, with any leftover available for touch-ups later.
Is my data private?
Completely. Every calculation runs entirely in your browser. Nothing you type is uploaded, stored or sent to a server, so you can estimate as many rooms as you like in total privacy.