How to Calculate Paint Quantity
Paint quantity is calculated as: Surface Area × Coats ÷ Coverage Rate. Coverage rate (m²/L) shows how far one liter goes. Standard latex covers the most at 12 m²/L; epoxy requires the most paint at 5 m²/L due to its thick film build.
In practice, corners, roller overlaps, and touch-ups add roughly 10% to your theoretical requirement. The waste margin field lets you account for this. Entering your can size shows how many full cans to buy and how much will be left over.
US standard interior latex cans are commonly 1 qt (0.95L) or 1 gal (3.78L). Set the can size field to match the product you plan to buy.
Frequently Asked Questions
Yes. Exterior paint must resist UV, moisture, and temperature swings. Use elastomeric or exterior-grade acrylic outside; standard latex works well indoors.
Yes. Fresh drywall, concrete, or plaster has high porosity and can absorb 20–30% more on the first coat. Use a primer or increase your waste margin to 15–20%.