Paint Calculator
Calculate paint gallons and liters needed for room walls.
Paint Calculator
Calculate how many gallons or liters of paint you need for room walls after deducting doors and windows.
What is the Paint Calculator and How Does It Work?
The Paint Calculator estimates how many gallons or liters of paint you need to cover a room's walls. It calculates the total wall area from your room dimensions, subtracts standard deductions for doors and windows, multiplies by the number of coats you plan to apply, and divides by typical paint coverage to give a shopping-ready quantity.
Wall area is the room's perimeter multiplied by ceiling height. Standard deductions of 21 sq ft per door and 15 sq ft per window are subtracted, then the result is multiplied by your number of coats and divided by typical paint coverage (350 sq ft per gallon).
Wall area = 2×(12+12)×8 = 384 sq ft; minus (21+30)=51 deductions = 333 sq ft net; ×2 coats = 666 sq ft ÷ 350 ≈ 1.9 gallons.
Wall area = 2×(20+15)×9 = 630 sq ft; minus (42+45)=87 deductions = 543 sq ft; ×1 coat ÷ 350 ≈ 1.55 gallons.
Common Real-World Use Cases
Buy the right number of paint cans before starting a repaint project, avoiding extra trips to the store.
Estimate paint material costs as part of a larger renovation or home-flip budget.
Give homeowners a quick, defensible material estimate before a formal quote.
- 1Enter your room's length, width, and ceiling height.
- 2Enter the number of doors and windows to deduct from the paintable area.
- 3Set how many coats of paint you plan to apply.
- 4View the total gallons and liters needed, rounded up to the nearest full can.
- •Always round up to the next full gallon or can - paint stores rarely sell partial containers.
- •Darker colors or major color changes may need an extra coat beyond the standard 2.
- •Coverage of 350 sq ft per gallon is a common average; check your specific paint can label for its exact coverage rate.
Frequently Asked Questions
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