Unkillable Tools / Calculator / How much paint do I need?
Gallons and cost from the wall area you actually have to paint — with doors and windows deducted, which is where most estimates go wrong.
Enter your room's perimeter rather than measuring each wall separately.
Change the rates, the labels and the maths to match your business, then export it as a single HTML file you paste into your site. Free, no account, and it keeps working whatever happens to us.
Open the builderAdding up the length of every wall and multiplying by ceiling height is the same as perimeter × height, and it's far less error-prone to ask for one number than four.
Deduct roughly 21 square feet per door and 15 per window. These are averages and they matter: a room with three windows and two doors has nearly 100 square feet you don't need to cover, which is a third of a gallon.
A gallon covers about 350 square feet on a smooth, previously painted surface. Textured, porous or fresh drywall drinks noticeably more — closer to 250 to 300.
Two coats is the realistic default. One coat only works when you're going over a near-identical colour, and a calculator that defaults to one coat will consistently send people back to the shop.
The result rounds up to whole gallons, because that's how paint is sold. Buying 2.4 gallons is not an option.
No — it calculates wall area. For a ceiling, add its length × width as a separate input.
Add a coats field for primer with its own price, or just add one to the coat count for a rough figure.
Yes. Build it, set your own prices, export the file and paste it in. Free, no subscription.
Hosted calculator builders charge $5–$115 a month and stop rendering when you exceed your monthly impressions. This one exports a file that runs on your own site and cannot be switched off.
Build one free