What does this tool do?
The Paint Calculator estimates how many liters of paint you need from your room measurements. Enter each room's width, length, and height, subtract doors and windows, then set the number of coats and the coverage rate. It is a quick planning tool for homeowners, renters, and painters heading to the store.
How to use it
- Enter your values into the fields.
- The result is calculated instantly.
- Read or copy the result.
How the calculation works
For each room the tool finds the wall area as perimeter × height, that is 2 × (width + length) × height. It then subtracts roughly 1.52 m² for every door and 1.08 m² for every window. The resulting net area is multiplied by your chosen number of coats and divided by the coverage rate in m² per liter to give the paint needed. You can add several rooms at once, switch between meters and feet, and copy any result.
Choosing the right coverage value
Coverage (m²/L) is the area one liter of paint covers, and it varies by brand. Most interior wall paints cover about 10–12 m² per liter in a single coat, while rough, porous, or freshly plastered surfaces cover less. For an accurate estimate, enter the value printed on your paint tin. If you also plan to paint ceilings, consider adding the room's floor area as a separate "room" or leave a margin in your total.
Frequently asked questions
Does it include the ceiling?
No, the calculation covers only the four walls. For the ceiling, add the floor area (width × length) as a separate entry or add it to the result manually.
What sizes are assumed for doors and windows?
Each door is treated as 1.9 × 0.8 m and each window as 1.2 × 0.9 m, then deducted from the wall area. Adjust the counts if your openings differ greatly in size.
Should I add extra for waste?
Yes. It is wise to buy roughly 10% more paint to cover spillage, touch-ups, and the chance of needing a second batch in the same shade.
Is Paint Calculator free?
Yes. Paint Calculator and all 300+ tools on MagmaNex are completely free with no signup or account required.
Is my data safe?
Yes. Everything runs locally in your browser. The data you enter is never sent to a server, stored, or shared.
Does it work on mobile?
Yes. Paint Calculator works on phones, tablets and desktops — no app download needed.
🔒 Privacy: everything runs in your browser, your data is never sent to a server.