Part of the Construction collection — 4 tools available
Paint Calculator — How Much Paint Do You Need?
Figure out how many gallons of paint you need for any room. Accounts for walls, ceiling, doors, windows, and number of coats for an accurate estimate.
About This Calculator
Nothing kills a painting project faster than running out of paint halfway through the second coat — or buying four gallons when two would do. Room dimensions alone aren't enough; you need to subtract door and window openings and account for the number of coats you plan to apply. Textured walls further reduce coverage by 20-30% compared to smooth surfaces, adding another layer of complexity. Our paint calculator factors in all of these variables — room dimensions, standard door and window deductions, number of coats, and optional ceiling coverage — so you walk into the hardware store knowing exactly how many gallons to buy for the job.
The Formula Behind This Calculator
Net area = Walls area - Doors (20 sq ft) - Windows (15 sq ft) Gallons = Net area / 350 (per coat) 2 coats = Gallons * 2 Cost = Gallons * Price
Understanding the math helps you verify results and make better decisions for your project.
Related Tools
How to Use
- 1Enter room length and width in feet.
- 2Set the ceiling height.
- 3Count the number of doors and windows.
- 4Choose number of coats (2 is standard).
- 5Set include ceiling to 1 if painting the ceiling too.
- 6Click Calculate for total gallons needed.
When to Use
- →Estimating paint before a trip to the hardware store so you buy the right amount in one trip
- →Budgeting paint costs for a whole-house interior or exterior repaint project
- →Comparing coverage between different paint brands or primer-plus-paint combos
Tips
- ✓Buy an extra quart for touch-ups — store it labeled with the room name and color code for future use
- ✓Textured walls reduce coverage by 20-30%; increase your estimate if you have knockdown or stucco finishes
- ✓Two thin coats always look better and last longer than one thick coat, even if the label says one-coat coverage
FAQ
How much does one gallon of paint cover?
About 350-400 sq ft per coat on smooth surfaces. Rough or textured walls may reduce coverage to 250-300 sq ft.
Do I need primer before painting?
Yes when painting over dark colors with light ones, on new drywall, or covering stains. Primer covers about 300-400 sq ft per gallon.
How many coats of paint should I apply?
Two coats is standard. Three may be needed when going light over dark or with low-opacity colors like reds and yellows.
Should I paint the ceiling first or walls?
Always ceiling first — splatter gets covered when you paint the walls, saving touch-up time.
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