Construction Calculator - Construction Converters

Gallons per Square Foot Calculator

Convert liquid depth over an area into gallons.

Reviewed: August 26, 2026

Calculate Gallons per Square Foot

For the Gallons per Square Foot Calculator, enter area and liquid depth. It converts area and liquid depth into cubic feet, U.S. gallons, and liters for a uniform-depth layer.

Construction measuring tools arranged beside a residential building project

Formula used

U.S. gallons = surface area × (liquid depth ÷ 12) × 7.48052

Gallons per Square Foot Calculator measurement plan showing Area square feet, Liquid depth inches

Worked gallons per square foot example

Gallons per Square Foot Calculator example: 670 ft² × (1 in ÷ 12) = 55.83 ft³. Multiplying by 7.48052 gives approximately 417.66 U.S. gallons.

Interpret gallons and flow

Use the result for shallow flooding, rainfall capture, coating flood tests, or storage planning only when a uniform-depth model is reasonable.

System effects the formula omits

Surface slope, low spots, freeboard, absorption, displacement, and nonuniform application depth affect actual liquid volume.

Questions specific to this calculation

Does the liquid-depth estimate allow for an uneven surface?

Enter surface area and a uniform liquid depth. One inch over a square foot is converted through cubic feet to U.S. gallons.