Cubic Feet to Gallons Converter

How to use the cubic feet to gallons converter

1. Enter a value in Cubic feet or US gallons. Leave the other field empty.
2. The converter calculates the equivalent volume immediately as you type.
3. Read the result below the fields, shown to eight decimal places for precision.

How the conversion works

The relationship between cubic feet and US gallons comes from their exact metric definitions. One US gallon is defined as exactly 231 cubic inches, and one cubic foot contains 1,728 cubic inches (12 multiplied by 12 multiplied by 12). Dividing gives the conversion factor:

1 ft³ = 1728 / 231 = 7.48051948... US gallons

To convert cubic feet to gallons, multiply by this factor. To go the other way, divide by it. For example, a 10 cubic foot container holds 10 x 7.48051948 = 74.80519481 US gallons. The math is straightforward but the repeating decimal means rounding errors accumulate quickly if you use a truncated factor like 7.48.

Common volume reference table

This table shows frequently used conversions between cubic feet and US gallons. Values are rounded to four decimal places for readability.

Keep in mind that these figures apply only to US liquid gallons. If your project specifies Imperial gallons, the numbers will be roughly 20 percent smaller for the same cubic footage.

Practical applications

Converting cubic feet to gallons is common when sizing water storage tanks, aquariums, swimming pools and HVAC equipment. Pool builders often calculate the volume of an excavation in cubic feet, then need the result in gallons to determine chemical dosing or pump capacity. A typical residential pool might hold 2,000 cubic feet, which translates to nearly 15,000 gallons.

In agriculture, irrigation planners measure reservoir capacity in acre-feet or cubic feet but purchase liquid fertilizers by the gallon. Having a reliable volume converter avoids rounding errors that compound over large quantities. Municipal water systems also rely on this conversion: flow meters may report in cubic feet per second while billing departments charge per thousand gallons.

If you also need to convert between smaller liquid measures, tools like quarts to gallons handle kitchen and laboratory scale volumes where cubic feet would be impractically large.

US gallons versus Imperial gallons

This tool uses US liquid gallons exclusively. The US gallon is defined as exactly 3.785411784 liters. The UK Imperial gallon, still used in some Commonwealth countries, is larger at exactly 4.54609 liters. Because the two differ by about 20 percent, mixing them up leads to significant errors in large-volume calculations.

One cubic foot equals approximately 6.2288 Imperial gallons, not 7.4805. Always confirm which gallon standard your project requires before converting. Equipment manuals from British manufacturers typically specify Imperial gallons, while American plumbing codes use US gallons. When in doubt, check the liter equivalent printed on the vessel or stated in the documentation.

Related length and area conversions

Volume conversions often start with linear or area measurements. If you measured a room or tank in centimeters, you may first need to convert to feet using a cm to feet tool before cubing the dimensions. Similarly, if you have a floor area in metric units, converting square meters to square feet lets you multiply by depth in feet to arrive at cubic feet, which you can then convert to gallons here.

For example, a rectangular tank measuring 3 meters by 2 meters with a depth of 1.5 meters has a volume of 9 cubic meters. Converting that area to square feet and multiplying by the depth in feet yields the cubic footage needed for this calculator. Chaining converters this way keeps each step transparent and easy to verify.

Worked examples

Each result below was produced by the same code the tool runs, so you can check your own numbers against them.