Paint Calculator
Room dimensions
Enter the size of your room to find out how much paint to buy.
For 2 coats of paint
Area breakdown
- Wall area (Gross)
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- Ceiling area
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- Doors & Windows (Subtracted)
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- Total Paintable Area
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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, multiplies the net surface 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 each one individually.
- Coverage Customization: Adjust the coverage rate if you are using specialized thick primer, textured finishes, 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, brick, or stucco may absorb more paint and require 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, roller absorption, or future color matching. Our calculator's "Recommended buy" automatically rounds up to the nearest whole container.
What size are the default doors and windows in the calculator?
To keep calculations quick, 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 room has larger glass doors or picture windows, you can increase the item count to compensate.
Do I need a primer?
Primer is necessary if you are painting over a dark color with a lighter shade, painting freshly taped drywall, patching stains, or transitioning from oil-based to water-based paint. Primer usually covers slightly less area than finish paint (around 200–300 sq ft per gallon).
Helpful Next Steps & Related Calculations
Explore tools that naturally complement your home improvement and everyday planning.
- Hanging artwork or mirrors on your freshly painted walls? Use our Picture Hanging Calculator for perfectly spaced and leveled wall decor.
- Planning your renovation budget or hiring professional painters? Try our Tip & Bill Split Calculator to calculate service gratuities and labor totals.
- Working on late-night painting projects? Optimize your sleep cycle with our Sleep Calculator to wake up energized between coats.