Free Online Paint Calculator
Calculate How Many Gallons of Paint You Need
Need to use Paint Calculator right now?
Buying too little paint means a second trip to the store mid-project and the risk of a slightly different batch tint; buying too much wastes money on a product that's hard to return once opened. Getting the gallon count right up front depends on the room's wall area, how many coats you're applying, and how much of that area is actually openings — doors and windows — that don't need paint at all.
Assumes standard one-coat coverage of 350 sq ft per gallon, and 20 sq ft deducted per door/window opening.
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Features
- Runs entirely in your browser
- Privacy-first — your data is never uploaded
- Real-time, instant results
- 100% free, no sign-up required
- Works on desktop, tablet, and mobile
- No installation needed
Who uses this tool?
About Paint Calculator
Buying too little paint means a second trip to the store mid-project and the risk of a slightly different batch tint; buying too much wastes money on a product that's hard to return once opened. Getting the gallon count right up front depends on the room's wall area, how many coats you're applying, and how much of that area is actually openings — doors and windows — that don't need paint at all.
This calculator takes your room's length, width, and ceiling height, subtracts the area taken up by doors and windows, and multiplies by your number of coats to get total paintable square footage. It then divides by a standard coverage rate of 350 square feet per gallon — the typical spread rate most interior paints list on their can — to tell you exactly how many gallons to buy.
Everything runs instantly in your browser as you adjust dimensions, so you can quickly compare scenarios: one coat versus two, a room with a lot of windows versus a windowless one, or a larger accent wall versus the whole room.
How it works
- Enter room dimensions. Input the room's length, width, and ceiling height in feet.
- Subtract openings. Enter the total square footage of doors and windows to exclude.
- Set number of coats. Choose one or two coats — the calculator scales the gallons needed accordingly.
Examples
12ft x 10ft room, 8ft ceilings, 2 coats
Input
Length: 12, Width: 10, Height: 8, Openings: 40 sq ft, Coats: 2
Output
≈ 2.1 gallons needed