Gallons per Square Foot Calculator
Quickly determine the amount of liquid (in gallons) used per square foot of area.
How to use this calculator
Enter the total liquid volume in gallons and the covered area in square feet, then select Calculate. Use a positive area. The result is the amount of liquid used for each square foot, not the total amount required for a new job.
FORMULA AND WORKED EXAMPLE
Gallons per square foot = total gallons ÷ covered area. If 10 gallons cover 500 ft², the result is 0.02 gallons/ft². If 15 gallons cover the same area, the result rises to 0.03 gallons/ft². A larger number means more liquid was used per unit of surface.
COVERAGE VERSUS APPLICATION RATE
A product label may give square feet per gallon instead. This is the reciprocal of gallons per square foot: 0.02 gallons/ft² corresponds to 50 ft²/gallon. Dividing a new area by 50 ft²/gallon estimates the gallons required at that coverage. For example, 750 ft² would require 15 gallons before any separate allowance. Do not confuse these two measures when comparing products.
KEEP THE MEASUREMENT BASIS CONSISTENT
Use square feet for area, rather than a length measured in feet. If a rectangle is 20 ft by 25 ft, first multiply those dimensions to obtain 500 ft². US and Imperial gallons have different volumes. This tool calculates a ratio from the gallon quantity entered; use the same gallon definition throughout your comparison.
PLAN FOR REAL APPLICATION CONDITIONS
Porous surfaces, texture, overspray, spills, and the number of coats can change actual usage. State whether the measured gallons cover one coat or the whole job. A ratio from a previous project is a comparison point, not a guarantee of future coverage. Follow the product’s instructions for recommended application rates and calculate any waste allowance separately.