Coverage states how much area one unit of paint is expected to cover under manufacturer conditions. PaintCalc accepts m²/L or ft²/US gal because those ratios connect coated area to volume. The field intentionally starts empty. A number borrowed from another brand, finish, line, substrate, or application method creates a precise-looking answer from the wrong input. Find the value on the exact container or current datasheet and keep its units and conditions beside the number.
Read the ratio in the correct direction
10 m²/L means one litre is stated to cover ten square metres. 350 ft²/US gal means one US gallon is stated to cover 350 square feet. Required volume equals coated area divided by coverage. Do not invert the ratio or mix litres with square feet. PaintCalc separates metric and imperial and means US gallons, not imperial gallons. Coverage is not a law: the sheet may describe a range, dry-film thickness, prepared surface, or method. Porosity, texture, colour change, spray, absorption, and technique can change real consumption.
Calculate volume before container rounding
PaintCalc does not choose inside a range, add secret waste, or adjust conditions. Select a value you can justify or seek advice, then record its source and date. Multiply net area by chosen whole coats and divide by exact coverage. Keep litres or US gallons visible before packaging. Container volume is separate: divide required volume by it and round upward. Leftover caused by package rounding is not changed coverage or an allowance. Verify coverage and container volume belong to the same exact variant, then consider supplier guidance, return rules, and on-site judgment.