🎨 Paint Calculator
Enter your room dimensions, wall height, and number of coats to find how many gallons of paint to buy — with doors, windows, and coverage accounted for.
🎨 Room & Coverage Details
What is a Paint Calculator?
It turns your room measurements into the amount of paint to buy. From the wall perimeter and height it works out the wall area, subtracts an allowance for doors and windows, multiplies by the number of coats, and divides by the paint's coverage per gallon — rounding up so you finish the job without a mid-wall run to the store.
Use it to budget a single accent wall or a whole-room repaint, right-size how much you buy, and keep a little leftover for touch-ups. The figures are estimates for planning — confirm coverage on the can and allow extra for rough or unprimed surfaces.
❓ Frequently Asked Questions
How does the calculator estimate how much paint I need?
It computes the wall area — the room perimeter (twice the length plus width) times the wall height — and subtracts about 15 square feet for each door or window. It multiplies that area by the number of coats, divides by the coverage of a gallon (350 square feet by default), and rounds up to whole gallons, since paint is sold by the can.
How many coats should I plan for?
Two coats is the standard for an even, durable finish and the default here. Plan for a third when you're going from a dark color to a light one, covering patchy or stained walls, or using a color that's hard to cover such as a deep red. A tinted primer coat can reduce how many finish coats you need.
What coverage figure should I use?
Most interior wall paints cover 350 to 400 square feet per gallon on a smooth, primed surface, and 350 is a safe default. Rough, porous, or previously unpainted surfaces soak up more and cover less, so drop the figure if your walls are textured or bare. Always check the coverage printed on the can.
Does it include the ceiling, trim, or primer?
No — it estimates the wall area only. Add the ceiling area separately (length times width) if you're painting it, and buy trim and primer on their own, since they use different products and coverage rates. Keeping a little leftover wall paint for touch-ups is always worthwhile.