Paint Calculator

Calculate the exact amount of paint you need for your room by entering dimensions, exclusions, and coverage rate.

Room dimensions

Enter the size of your room to find out how much paint to buy.

Measurement unit Choose your preferred unit system.

Room length ft Room width ft Room height ft

Include ceiling Add the ceiling area to your paint calculation.

Doors and windows (to exclude)

Number of doors Subtracted at 21 sq ft each. Number of windows Subtracted at 15 sq ft each.

Paint details

Number of coats Paint coverage sq ft / gal Standard coverage is typically 350-400 sq ft per gallon.

About the Paint Calculator

This calculator helps you estimate the exact amount of paint needed for your next home improvement project. By inputting the dimensions of your room and the number of doors and windows, it subtracts the non-paintable areas and calculates your required paint volume.

How the calculation works

First, the calculator determines the total wall area (Length + Length + Width + Width) × Height. It then optionally adds the ceiling area (Length × Width). Finally, it subtracts the total area of doors and windows, then multiplies the result by the number of coats, and divides by your chosen paint's coverage rate.

Useful options

Metric & Imperial: Switch between feet/gallons and meters/liters seamlessly.
Exclusions: Quickly subtract standard-sized doors and windows without measuring them.
Coverage Customization: Adjust the coverage rate if you are using specialized thick primer or thin stains.

Frequently Asked Questions FAQs

How much area does one gallon of paint cover?

A standard gallon of interior acrylic paint typically covers between 350 and 400 square feet for a single coat. This translates to roughly 9 to 10 square meters per liter. Porous surfaces like bare drywall or stucco may require more paint or a primer first.

Should I buy extra paint?

Yes. It is highly recommended to round up and buy a little extra for touch-ups, spills, or color matching down the line. Our calculator's "Recommended buy" automatically suggests rounding up to the nearest whole container.

What size are the default doors and windows in the calculator?

To keep things simple, the calculator assumes a standard door is roughly 21 square feet (approx 1.95 sq m) and a standard window is 15 square feet (approx 1.4 sq m). If your features are significantly larger or smaller, you can adjust the count to compensate.

Do I need a primer?

Primer is necessary if you are painting over a dark color with a lighter one, painting new drywall, or transitioning from oil-based to water-based paint. Primer usually covers slightly less area than standard paint (around 200-300 sq ft per gallon).