TerraEvidence
Free rainfall-volume calculator

How many gallons does a rainfall depth represent?

Enter rain depth and the area it covered to calculate the geometric volume in U.S. gallons and litres. No location, account, or weather service is required.

Calculate rainfall volumeSee the exact method
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Only compatible length, width, and units are read after you choose import. Crop and location fields are not copied.

Transparent method

Rain depth multiplied by area

Metric geometry is direct: one millimetre over one square metre represents exactly one litre. U.S. calculations use the exact definitions of 231 cubic inches per U.S. gallon and 1,728 cubic inches per cubic foot.

U.S. formulaU.S. gallons = area ft² × rain inches × 48 ÷ 77Metric formulalitres = area m² × rain mm

Example: 1 inch over 100 ft² represents approximately 62.338 U.S. gallons geometrically. Runoff, interception, evaporation, uneven gauge exposure, and infiltration are not calculated.