Cubic Feet to Gallons Converter
Convert volume between cubic feet, U.S. liquid gallons, and Imperial gallons with exact standard definitions and a downloadable Excel workbook.
Conversion inputs
Required. Enter a nonnegative decimal using a period as the decimal separator.
Changing the unit converts the current value so the represented volume stays the same.
Live results
Excel export is ready.
Conversion detail
| Measure | Value | Unit |
|---|---|---|
| Cubic feet | 12.500000 | ft³ |
| U.S. liquid gallons | 93.506494 | US gal |
| Imperial gallons | 77.860533 | Imp gal |
| Litres | 353.960400 | L |
| Cubic metres | 0.353960 | m³ |
The two gallon systems are different sizes. Use “U.S. liquid gallons” for the U.S. customary gallon and “Imperial gallons” for the U.K. imperial unit.
How to use the cubic feet to gallons calculator
What this calculator does. This converter expresses one volume in cubic feet, U.S. liquid gallons, Imperial gallons, litres, and cubic metres. It is useful when a tank, bin, pond, room, shipping container, or water-storage specification is stated in one system but your plan or equipment uses another. It performs an exact unit identity based on standard definitions; it does not estimate a container's usable capacity, account for wall thickness, freeboard, irregular geometry, temperature expansion, or how completely a vessel can be filled.
When to use it. Use the converter to translate a tank volume from cubic feet into gallons, compare U.S. and U.K. equipment ratings, check construction or landscaping quantities, or prepare consistent numbers for a worksheet, quote, or technical note. For regulated or contractual work, keep the original source unit and an appropriate number of significant figures.
How to calculate. The page opens with a ready-to-use demonstration of 12.5 cubic feet, and the Excel button is immediately available for that example.
- Enter the known amount in Volume. The field accepts ordinary nonnegative decimals such as 12.5 or 1000.25. Use a period for decimals; commas, scientific notation, unit text, negative numbers, and incomplete entries are rejected so they cannot be silently misread.
- Choose the matching Input unit: cubic feet, U.S. liquid gallons, or Imperial gallons. When you change this selector, the calculator converts the current entry so the physical volume remains unchanged rather than merely relabeling the number.
- Read U.S. liquid gallons as the primary result, then review Cubic feet, Imperial gallons, Litres, and Cubic metres. The formula line shows the active conversion path, while the detail table provides higher precision.
- Select Download Excel to create an OOXML workbook containing the current input, all converted results, conversion factors, units, and notes. Select Reset to clear the demonstration value. Reset may disable export until you enter another complete valid volume.
Input guide. Volume is required and must be a finite number from zero through 1e150. A realistic example is 12.5 ft³. Increasing it increases every result proportionally; zero converts exactly to zero. A common mistake is pasting “12,5” or “12 ft3,” which is ambiguous or contains unsupported unit text. Input unit is required and defines what the number means. Choose cubic feet for dimensions or capacity already expressed in ft³, U.S. liquid gallons for American liquid-volume specifications, and Imperial gallons for U.K. imperial specifications. The gallon choices are not interchangeable.
Output guide. U.S. liquid gallons is the equivalent volume using the U.S. gallon defined as 231 cubic inches. Cubic feet is the common base used internally. Imperial gallons uses the legally defined 4.54609-litre gallon. Litres and Cubic metres are metric equivalents. Every output is an exact conversion identity before display rounding, not a recommendation or capacity allowance. High or low values simply reflect the entered volume; negative output is never valid. The summary pills show the fixed one-cubic-foot factors, and the table columns list each measure, its canonical numeric value, and unit symbol.
Worked example. With the startup value of 12.5 ft³, multiply by 7.4805194805 to get 93.5065 U.S. gallons. The same 12.5 ft³ equals 77.8605 Imperial gallons, 353.9600 litres, and 0.3540 cubic metres. These first-open figures match the results panel, table, and workbook.
Learn more. NIST explains that sound unit conversion uses a defined factor and appropriate rounding. Its published conversion resources describe U.S. customary and SI relationships, while U.K. legislation defines the Imperial gallon as 4.54609 litres.
Conversion factors and practical interpretation
One international foot is exactly 0.3048 metre, so one cubic foot is exactly 0.028316846592 cubic metre, or 28.316846592 litres. One U.S. liquid gallon is exactly 3.785411784 litres. Dividing the cubic-foot volume by the U.S.-gallon volume gives 7.4805194805 U.S. gallons per cubic foot. The Imperial factor is different: 28.316846592 litres divided by 4.54609 litres per Imperial gallon equals about 6.228835459 Imperial gallons per cubic foot.
For water planning, remember that volume conversion alone does not determine weight, flow rate, pump sizing, or storage safety. The U.S. Geological Survey provides useful real-world context for visualizing large water volumes. A reservoir or tank may also require allowances for freeboard, sediment, fittings, and inaccessible space.
Rounding and common mistakes
Keep extra digits during the calculation and round once at the end. The results panel uses four decimals for practical readability, while the table and workbook retain more precision. Do not multiply a gallon value by the cubic-feet-to-gallons factor; reverse conversions require division by the applicable factor. Also verify whether a specification means U.S. liquid gallons or Imperial gallons. A quantity of 100 ft³ is about 748.052 U.S. gallons but only about 622.884 Imperial gallons, a difference large enough to matter in purchasing and capacity planning.