Cubic Feet to Gallons Calculator
To convert cubic feet to US liquid gallons, multiply the volume in cubic feet by 7.48051948. One cubic foot holds exactly 7.48051948 US liquid gallons of water at standard room temperature and pressure.
Standard Reference & Benchmark Chart
| Input Value | Converted Volume | Practical Application |
|---|---|---|
| 1 cu ft | 7.48 gallons | Standard reference benchmark |
| 5 cu ft | 37.40 gallons | Small rain barrel / compact tote |
| 10 cu ft | 74.81 gallons | Large aquarium or small water heater |
| 25 cu ft | 187.01 gallons | Medium agricultural stock tank |
| 50 cu ft | 374.03 gallons | Residential spa / hot tub capacity |
| 100 cu ft | 748.05 gallons | Commercial chemical tote (IBC container) |
| 500 cu ft | 3,740.26 gallons | Small backyard plunge pool |
| 1,000 cu ft | 7,480.52 gallons | Standard 15x30 ft residential swimming pool |
What is the Cubic Feet to Gallons Calculator?
The cubic foot (ft³) is an imperial and US customary unit of three-dimensional volume, defined as the volume of a cube with sides of one foot. The US liquid gallon (gal) is the standard commercial unit for fluid capacity, defined by NIST as exactly 231 cubic inches. Converting cubic feet to gallons is essential across residential plumbing, swimming pool construction, municipal water storage, and aquaculture. Because liquids conform to container walls, measuring external container dimensions in feet and transforming the resulting cubic footage into liquid capacity allows contractors and homeowners to precisely calculate water weights, chemical dosing, and pump flow rates.
Mathematical Formula & Unit Derivation
Gallons (US Liquid) = Cubic Feet (ft³) × 7.48051948 Step-by-Step Calculation Example
Suppose you have a rectangular residential water cistern measuring 8 feet long, 5 feet wide, and 4 feet deep. First, calculate total cubic feet: 8 ft × 5 ft × 4 ft = 160 ft³. Next, convert to US liquid gallons: 160 ft³ × 7.48051948 = 1,196.88 gallons. At approximately 8.34 lbs per gallon, this water weighs roughly 9,982 lbs.
Real-World Industry Applications
- Swimming Pools & Hot Tubs: Calculating total gallons to properly dose shock chlorine, stabilizer, and algaecide.
- Aquarium Volume: Sizing canister filtration systems and calculating live water weight for structural floor load limits.
- Rainwater Harvesting: Sizing rain barrels and retention tanks based on roof catchment area and average rainfall.
Common Measurement Mistakes to Avoid
- Confusing US Liquid Gallons with UK Imperial Gallons (1 cu ft = 6.2288 Imp gal).
- Confusing US Liquid Gallons with US Dry Gallons (1 cu ft = 6.4285 dry gal).
- Failing to subtract interior freeboard space (water level is typically 3-6 inches below the top edge).
💡 Expert Field Tips from Marcus Vance, PE
- For quick mental estimation on job sites, multiply cubic feet by 7.5 to get within 0.26% of the exact liquid gallon value.
- Remember that water expands when frozen; do not design outdoor storage tanks to 100% liquid capacity in freezing climates.
- Water exerts 62.4 pounds per cubic foot (approx. 8.34 lbs per gallon); ensure tank pads are engineered for dynamic fluid mass.
Related Field Guides & Case Studies
Frequently Asked Questions
How many gallons are in 1 cubic foot of water?
One cubic foot contains exactly 7.48051948 US liquid gallons. For everyday engineering estimations, 7.48 gallons is the accepted industry benchmark.
Is there a difference between US liquid gallons and UK gallons in cubic feet?
Yes, significant difference. 1 cubic foot equals 7.4805 US liquid gallons, but equals approximately 6.2288 UK Imperial gallons. UK gallons are roughly 20% larger in volume.
How do I calculate pool volume from cubic feet to gallons?
Multiply the pool's surface length by width by average depth in feet to get total cubic feet, then multiply that result by 7.4805. For circular pools, use (3.14159 × radius² × depth) × 7.4805.
How much does a cubic foot of water weigh in gallons?
A cubic foot contains 7.4805 gallons. Because one US gallon of fresh water weighs 8.34 lbs at room temperature, one cubic foot of water weighs approximately 62.4 pounds (28.3 kg).