Cubic Feet to Gallons Converter

The cubic feet to gallons converter transforms a volume expressed in cubic feet — the standard unit for tanks, pools, rooms, and containers in the US imperial system — into US gallons, imperial gallons, or liters for practical real-world applications.

A storage tank measuring 10 cubic feet holds exactly 74.805 US gallons, 62.288 imperial gallons, or 283.168 liters — four representations of the same volume that serve different applications from pool planning to fuel storage to aquarium sizing.

Use this free Cubic Feet to Gallons Converter to instantly convert any cubic feet measurement into US gallons, UK gallons, or liters. The reverse conversion — gallons to cubic feet — is also supported. No sign-up required.

What Is a Cubic Foot?

Cubic Foot Definition

A cubic foot is a unit of volume equal to the space occupied by a cube with sides measuring exactly one foot in every direction — one foot long, one foot wide, and one foot tall. It is the standard three-dimensional volume unit in the US customary and imperial measurement systems.

Cubic Foot — Definition

1 cubic foot (ft³) is the volume of a cube with edges of 1 foot (12 inches) in each dimension. It equals 1,728 cubic inches, 0.028317 cubic meters, 7.48052 US gallons, 6.22884 imperial gallons, or 28.3168 liters. Cubic feet measure three-dimensional space — tanks, pools, rooms, containers, and any enclosed volume.

Cubic feet are used whenever volume is derived from linear measurements in feet — pool dimensions, water heater tank capacity, refrigerator volume, aquarium size, furnace airflow, and concrete pour volumes. Converting cubic feet to gallons is necessary whenever volume must be expressed in liquid capacity terms for purchasing, filling, or chemical treatment calculations.

Cubic Feet to Gallons Conversion Formulas

Cubic Feet to US Gallons

The United States uses the US liquid gallon as its standard gallon. The exact conversion factor is:

Example: 5 ft³ × 7.48052 = 37.403 US gallons

The factor 7.48052 comes from the definition of the US liquid gallon as exactly 231 cubic inches, and 1 cubic foot containing exactly 1,728 cubic inches. Therefore: 1,728 ÷ 231 = 7.48052 gallons per cubic foot.

Cubic Feet to Imperial (UK) Gallons

The imperial gallon — used in the United Kingdom, Canada, and some other Commonwealth countries — is larger than the US gallon. The conversion factor is:

Example: 5 ft³ × 6.22884 = 31.144 imperial gallons

The imperial gallon is defined as exactly 4.54609 liters, compared to the US gallon which is exactly 3.78541 liters. This makes the imperial gallon approximately 20% larger than the US gallon — a critical distinction when ordering fuel, chemicals, or pool supplies across different countries.

Cubic Feet to Liters

For international applications and metric contexts, cubic feet convert to liters as follows:

Example: 5 ft³ × 28.3168 = 141.584 liters

Gallons to Cubic Feet — Reverse Conversion

To convert US gallons back to cubic feet, divide by the same conversion factor:

Example: 100 US gallons ÷ 7.48052 = 13.368 cubic feet

How to Calculate Cubic Feet from Tank Dimensions

When a tank or pool is described by its physical dimensions rather than a labeled capacity, calculate cubic feet first, then convert to gallons:

Example: A rectangular tank 4 ft × 2 ft × 1.5 ft = 12 cubic feet = 12 × 7.48052 = 89.766 US gallons

Cubic Feet to Gallons Quick Reference Conversion Table

How to Use the Cubic Feet to Gallons Converter

Step 1 — Determine Your Volume in Cubic Feet

If your tank, pool, or container displays its volume in cubic feet, use that figure directly. If you have the physical dimensions in feet, multiply length × width × height to get cubic feet first. If dimensions are in inches, divide each by 12 before multiplying, or use the cubic inches to cubic feet conversion: 1 ft³ = 1,728 in³.

Step 2 — Select Your Target Gallon Type

Choose US gallons for all US-based applications — swimming pools, water heaters, aquariums, fuel tanks, and water treatment. Choose imperial gallons when working with UK or Canadian standards, or when reading fuel economy specifications from Commonwealth-market vehicles. Choose liters for international shipping, chemical specifications, and metric-standard applications.

Step 3 — Enter the Value and Read the Result

Enter your cubic feet value in the converter field. The result appears instantly in all three output units simultaneously — US gallons, imperial gallons, and liters — so you can use whichever format your application requires without running multiple separate conversions.

Real-World Uses for Cubic Feet to Gallons Conversion

Swimming Pools and Hot Tubs

Pool volume in gallons determines the correct dosage of chlorine, pH adjusters, algaecide, and other water treatment chemicals. Pool dimensions are typically measured in feet — length, width, and average depth — which produces cubic feet. Converting to US gallons gives the volume needed for chemical treatment calculators.

• Rectangular pool: 20 ft × 10 ft × 4 ft average depth = 800 ft³ = 5,984 US gallons
• Round pool: Volume = π × radius² × depth. A 12 ft diameter pool at 4 ft deep = π × 6² × 4 = 452.4 ft³ = 3,384 US gallons
• Chemical dosing charts use gallons — without this conversion, you cannot correctly dose your pool
• Hot tub volumes are typically 200–500 US gallons, corresponding to 26.7–66.8 cubic feet

Water Heaters and Pressure Tanks

Residential water heater tanks are rated in gallons in the US, but plumbing plans and specifications may express storage volumes in cubic feet. A standard 50-gallon water heater occupies approximately 6.684 cubic feet of tank volume. When sizing a replacement unit or calculating a utility room’s spatial requirements, cubic feet to gallons conversion bridges the specification format used by plumbers versus the product labeling used by manufacturers.

Aquariums and Fish Tanks

Aquarium volume determines stocking density, filtration capacity, and water change schedules. Tank dimensions are measured in inches, which must first be converted to feet, then to cubic feet, then to gallons for fish-keeping applications. A standard 55-gallon aquarium measures 48 in × 13 in × 21 in — which equals 4.0 ft × 1.083 ft × 1.75 ft = 7.583 ft³ = 56.74 US gallons (slightly over the nominal 55-gallon rating due to glass thickness and fill level).

• Nano tanks: 10 gallons (1.337 ft³) — standard for shrimp and small fish
• Community tanks: 55–75 gallons (7.35–10.03 ft³) — standard residential aquarium
• Large display tanks: 120–200 gallons (16.04–26.74 ft³)

Fuel and Liquid Storage Tanks

Agricultural fuel tanks, industrial chemical storage, and emergency generator fuel tanks are often specified in cubic feet by engineers but must be procured in gallon capacity from suppliers. A 2 ft × 2 ft × 4 ft above-ground fuel tank has a volume of 16 cubic feet, equal to 119.69 US gallons — useful for determining how many full drums or deliveries are required to fill it.

HVAC and Air Volume

While HVAC calculations express airflow in cubic feet per minute (CFM) rather than gallons, engineers sometimes need to convert room volume from cubic feet to liters for refrigerant calculations or to gallons for humidifier sizing. A 12 ft × 15 ft × 9 ft bedroom contains 1,620 cubic feet = 12,118 US gallons of air — a figure used in whole-home humidifier capacity calculations.

US Gallon vs. Imperial Gallon — Critical Difference

How Much Bigger Is an Imperial Gallon than a US Gallon?

The imperial gallon is approximately 20% larger than the US gallon. This difference is not trivial — it affects every fuel economy comparison, chemical dosing calculation, and liquid capacity specification between US and UK sources.

Important:  Never mix US gallon and imperial gallon figures in the same calculation. A UK vehicle fuel economy rating of 40 mpg (imperial) equals only 33.3 mpg on the US gallon scale — a 20% difference. Similarly, a US pool chemical dosing chart based on US gallons will significantly underdose if you enter your pool volume in imperial gallons. Always confirm which gallon standard your source document uses before converting.

Final Thoughts

Converting cubic feet to gallons is one of the most practical volume calculations in everyday construction, plumbing, pool care, and appliance sizing. The conversion factor is fixed and exact: 1 cubic foot = 7.48052 US gallons = 6.22884 imperial gallons = 28.3168 liters. The only variable is which gallon standard applies to your application — always confirm US versus imperial before calculating chemical doses, fuel quantities, or equipment specifications.

See also: Cubic Feet Calculator, Cubic Yard Calculator, Gallons to Pounds Converter, Kg to Liter Converter

Frequently Asked Questions

How many gallons are in a cubic foot?

There are exactly 7.48052 US liquid gallons in one cubic foot. This figure comes from the definition of the US gallon as 231 cubic inches and one cubic foot containing 1,728 cubic inches: 1,728 ÷ 231 = 7.48052. For imperial (UK) gallons, 1 cubic foot contains 6.22884 gallons. For liters, 1 cubic foot equals 28.3168 liters.

How do I convert cubic feet to gallons?

Multiply cubic feet by 7.48052 to get US gallons. Multiply by 6.22884 for imperial gallons. Multiply by 28.3168 for liters. Example: 8 cubic feet × 7.48052 = 59.844 US gallons. For large volumes, use the calculator for precision — manual multiplication with the full conversion factor avoids rounding errors that accumulate in chemical dosing calculations.

How do I calculate the gallons in a rectangular tank?

Measure the tank’s internal length, width, and height in feet. Multiply them together to get cubic feet: Volume (ft³) = Length × Width × Height. Then multiply by 7.48052 to get US gallons. Example: A tank measuring 3 ft × 2 ft × 2 ft = 12 ft³ × 7.48052 = 89.766 US gallons. If dimensions are in inches, divide each by 12 before multiplying.

What is the difference between a US gallon and an imperial gallon?

The US gallon equals 231 cubic inches or 3.78541 liters. The imperial (UK) gallon equals 277.42 cubic inches or 4.54609 liters — approximately 20% larger. One cubic foot contains 7.481 US gallons but only 6.229 imperial gallons. Always confirm which gallon standard applies before using a conversion result for fuel, chemical, or liquid capacity calculations.

How many gallons does a 10 cubic foot tank hold?

A 10 cubic foot tank holds 74.805 US gallons, 62.288 imperial gallons, or 283.168 liters. This is a common size for intermediate bulk storage, large aquariums, and residential pressure tanks. At 74.8 US gallons, it sits between a standard 65-gallon and 80-gallon water heater in capacity.

How do I convert gallons to cubic feet?

Divide US gallons by 7.48052 to get cubic feet. Divide imperial gallons by 6.22884. Divide liters by 28.3168. Example: 100 US gallons ÷ 7.48052 = 13.368 cubic feet. This reverse conversion is useful when you know a tank’s gallon capacity and need to determine how much physical space it requires for installation planning.

Why do cubic feet and gallons use different measurement systems?

Cubic feet measure three-dimensional space using the foot as the base length unit — part of the US customary and imperial measurement systems. Gallons measure liquid volume capacity — also part of the imperial system, but defined independently from the cubic foot through historical British and American standards. The two systems overlap but were defined separately, which is why the conversion factor (7.48052) is not a round number.

About This Calculator

This cubic feet to gallons converter is part of Intelligent Calculator’s Conversion suite — built on NIST unit conversion standards and international measurement definitions. US gallon = 231 in³ exactly. Imperial gallon = 4.54609 L exactly. 1 foot = 0.3048 m exactly. Free. No sign-up required.