Cubic Feet to Gallons
Change cubic feet to gallons, or find how many gallons a tank or box holds.
Type an amount
Your answer
1 cubic foot · 28.32 liters
That much water weighs
62.4 lb.
Water weighs about 8.34 lb a gallon. NIST says a US gallon of water at 62 °F weighs about 8⅓ lb.
Quick answers
- 1 cubic foot
- 7.48 US gallons, or about 28.3 liters.
- 1 US gallon
- 0.134 cubic feet. That is 231 cubic inches.
- A 5 gallon bucket
- About 0.668 cubic feet. Filled to the brim, about 0.695–0.727 cubic feet.
- What water weighs
- About 8.34 lb a gallon, or 62.4 lb a cubic foot.
- 100 cubic feet
- 748.1 US gallons.
How to work it out
- Have cubic feet? Multiply by 7.48 to get gallons.
- Have gallons? Divide by 7.48 to get cubic feet.
- For a box or tank, first multiply length × width × depth in feet. That gives cubic feet.
- Sizes in inches? Multiply them, then divide by 231 for gallons.
5 cubic feet × 7.48 = 37.4 gallons
37.4 gallons × 8.34 lb = 311.9 lb of water
Where 7.48 comes from
Need cubic yards, not gallons? Our cubic feet to yards page does that.
NIST, the US standards office, defines the US gallon as 231 cubic inches. It is in NIST's unit tables.
A cubic foot is 12 × 12 × 12 in, which is 1,728 cubic inches. So it holds 1,728 ÷ 231 = 7.48 gallons, rounded.
NIST also sets one gallon at 3.785 liters. That puts a cubic foot at about 28.3 liters.
Common amounts
| Cubic feet | Gallons | Liters | Water weighs |
|---|---|---|---|
| 0.5 | 3.74 | 14.2 | 31.2 lb |
| 1 | 7.48 | 28.3 | 62.4 lb |
| 2 | 14.96 | 56.6 | 125 lb |
| 5 | 37.4 | 141.6 | 312 lb |
| 10 | 74.81 | 283.2 | 624 lb |
| 27 (1 cubic yard) | 202 | 764.6 | 1,684 lb |
| 100 | 748.1 | 2,831.7 | 6,239 lb |
Gallons are rounded as in the calculator, liters to 1 decimal. Water at 8.34 lb a gallon.
| Gallons | Cubic feet |
|---|---|
| 1 | 0.134 |
| 5 | 0.668 |
| 10 | 1.34 |
| 50 | 6.68 |
| 100 | 13.37 |
| 500 | 66.84 |
| 1,000 | 133.7 |
Is a 5 gallon bucket really 5 gallons?
Up to its fill line, yes. The Cary Company sells its pail as 5 gallons, which is 0.668 cubic feet.
Filled to the brim, a bucket holds a bit more. Uline and Container Supply list 5.2–5.44 gallons for their pails. That is 0.695–0.727 cubic feet.
Some products sold as "5 gallon" hold less. A Black Jack driveway sealer pail holds 4.75 gallons, or 0.635 cubic feet.
Filled with water to the 5 gallon mark, the water weighs about 41.7 lb. A cubic foot takes about 1.5 buckets, and a cubic yard about 40.
What water weighs
A Minnesota state agency sheet says a gallon of water weighs 8.34 lb. It puts a cubic foot at 62.4 lb. The US Bureau of Reclamation also says 62.4 lb a cubic foot.
The state sheet gives no water temperature. NIST says a US gallon of water at 62 °F weighs about 8⅓ lb. That is very close to the state's 8.34 lb.
How the calculator works out a tank
Pick "A box" in the calculator for a square or long tank. It multiplies length × width × depth, then × 7.48.
For a box 4 × 3 × 2 ft, that is 24 cubic feet, or 179.5 gallons. Full of water, it weighs about 1,497 lb.
Pick "A round tank" for a round one. Type the width across and the depth. The calculator halves the width, then does half × half × 3.142 × depth.
A round tank 3 ft across and 2 ft deep holds 14.14 cubic feet, or 105.8 gallons.
Both answers are to the brim. Fill a little less to leave room.
A full tank is heavy. Before you set one on a deck or floor, check your local building rules or ask a builder or engineer.
Measuring a tank or box
- Measure inside the walls. The walls take up space that can't hold water.
- For a round tank, measure straight across the middle, at the widest point.
- For depth, measure how deep you will fill it, not just the full height.
- Use one unit for all three sizes: all feet or all inches.
- If your tape reads inches, pick "Inches" in the calculator. It changes them to feet for you.
Questions people ask
How many gallons are in a cubic foot?
7.48 US gallons. NIST sets a gallon at 231 cubic inches. A cubic foot holds 1,728 cubic inches, and 1,728 ÷ 231 = 7.48.
How many cubic feet is a 5 gallon bucket?
About 0.668 cubic feet, filled to the 5 gallon mark. Filled to the brim, it is about 0.695–0.727 cubic feet.
How many cubic feet is a gallon of water?
0.134 cubic feet. A gallon of water takes the same space as a gallon of anything else.
How many gallons is 100 cubic feet of water?
748.1 gallons. That much water weighs about 6,239 lb.
How many gallons is 5 cubic feet?
37.4 gallons. And 2 cubic feet is 14.96 gallons.
How do you calculate gallons from cubic feet?
Multiply the cubic feet by 7.48. If you have a tank's size in feet, multiply length × width × depth first.
How much does a cubic foot of water weigh?
About 62.4 lb, say the US Bureau of Reclamation and a Minnesota state agency.
How many liters are in a cubic foot?
About 28.3 liters. NIST sets one US gallon at 3.785 liters.
Where our numbers come from
- Unit sizes: NIST Handbook 44, Appendix C (1 ft = 0.3048 m; 1 US gallon = 231 cubic inches)
- Water weight: Minnesota Pollution Control Agency formula sheet (8.34 lb per gallon)
- Water weight: US Bureau of Reclamation (62.4 lb per cubic foot)
- Water weight with temperature: NIST Handbook 44, Appendix B
- 5 gallon bucket size: The Cary Company pail (5 gallons nominal)
- 5 gallon bucket to the brim: Uline pail (5.4 gallons)
- 5 gallon bucket to the brim: Container Supply Co. (5.44 gallons)
- Sealer coverage and drying: Black Jack Drive-Maxx 200 product sheet
Made by BuildersCount. Last checked 3 Oct 2026.
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