Online Water Calculator to Convert Gallons to Acre Feet or Cubic Feet 

An acre-foot is a common unit to measure volumes of water, typically for use in irrigation. One acre-foot is the volume of water sufficient to cover an acre of land to a depth of 1 foot (43,560 cubic feet, approximately 325,851 U.S. gallons, or approximately 1,233.48 cubic meters). On average, 1 acre-foot of water is enough to meet the demands of 4 people for a year.  This calculator is not for acre-feet per annum (AFA); go to the table of formulas/calculators for AFA calculations.

Gallons to AF (or cubic feet) Conversion Calculator

DISCLAIMER: Use at your own risk, and doublecheck the math with your own calculator. You should also check with your hydrologist or water lawyer to make sure that the formulas are correct for your state. The calculator will work with Internet Explorer, Firefox and Netscape 6.0 (and higher).

The exact number of gallons per acre-foot equals 325,851.385 gallons. Generally, most people calculate the conversion without the decimal. 325,851 is the base used in the calculator below.

 How to use the calculator. (1) Enter the number of gallons you wish to convert in the top of the form. DO NOT USE COMMAS. (2) Select acre-feet or cubic feet. (3) Click "Calculate. The converted expression will appear in the last box (conversion). If you selected acre-feet, the converted figure is an expression in acre-feet. To recalculate with a different expression (for example, cubic feet instead of acre-feet), be sure to select cubic feet in the drop down menu, and click the calculate button again so that the math will reset. If you don't understand this, experiment using 325851 gallons. The result will be 1 acre-foot, which will match the formula above. Or with cubic feet, type in 7.48 gallons and the result will be 1 cubic foot.  

Programming Notes: Thanks go to the JavaScript Source for basic code (Gordon Hudson; VAT calculations) which was rewritten for purposes of these calculations.