Gallons to Liters Calculator

A US gallon can describe gasoline at a pump, a five-gallon water jug, a home-brewing batch, a fish tank, or a cleaning concentrate. Liters are the metric volume unit used on international labels, scientific notes, many appliance manuals, and most non-US fuel records. Select the starting unit, enter a nonnegative volume, and the calculator converts in either direction using exactly 3.785411784 liters per US liquid gallon.

Use gallons-to-liters for a US container, receipt, or tank plate that needs a metric value. Switch to liters-to-gallons when the source is a metric label or record. For a broader unit menu, the volume converter and gallon calculator connect gallons with cups, pints, quarts, fluid ounces, cubic inches, cubic feet, milliliters, and other common volume units.

US gallons, liters, and litres

A US liquid gallon is the gallon used for liquid volume in the United States. It equals 231 cubic inches. The international inch is exactly 0.0254 m, so 231 × 0.0254³ × 1,000 gives exactly 3.785411784 L. A liter is a metric unit of volume equal to one cubic decimeter. The spelling litre means the same unit, so a Canadian product label that says litres and a US calculator result that says liters are using the same L symbol.

The phrase “gallon” is the main trap. A US liquid gallon is not the same as an imperial gallon. The imperial gallon is about 4.54609 L and is still seen in some UK and Commonwealth contexts. If a fuel, beer, or historical capacity table says imperial gallons, do not enter that number here unless you first convert it to US gallons or accept the difference.

Formula used by the calculator

For gallons to liters, the form applies:

$\text{liters} = \text{US gallons} \times 3.785411784$

For the inverse direction:

$\text{US gallons} = \frac{\text{liters}}{3.785411784}$

The displayed result is rounded to two decimal places. That means very small volumes can round noticeably, while household and fuel volumes remain easy to read.

Conversion example using the stated method

Suppose a water container is labeled 12 US gal. The calculator evaluates:

$\text{liters} = 12 \times 3.785411784 = 45.424941408$

The primary answer is displayed as 45.42 L. The copy text also keeps the source unit clear: 12 gal = 45.42 L. If the same 12 had been imperial gallons, the correct liter value would be about 54.55 L, which is why identifying the gallon standard matters before using the result.

Reference table

Where gallons-to-liters conversions matter

Fuel records often start in gallons in the United States and need liters for international comparisons. Convert the purchased gallons here, then combine the liter result with a distance metric in the fuel economy converter. Aquarium care is another gallons-first domain: tank marketing names are often in gallons, while conditioners, fertilizers, and medications may dose per liter. Convert the true water volume, not just the tank name, because gravel, decorations, sump levels, and freeboard reduce usable water.

Recipes and beverage batches can also start in gallons, especially for brines, punch, stock, homebrewing, and institutional kitchens. Metric scales and bottles usually read liters or milliliters, so converting before scaling prevents a half-gallon from being treated as two liters exactly. Emergency water storage plans frequently use gallons per person per day, while container labels may use liters. Converting the plan in the same direction keeps the planning assumption visible.

Pitfalls to avoid

• Do not use this for imperial gallons. Imperial gallons are larger, so the liter result would be too low.
• Do not round each intermediate value when adding several containers. Add gallons first, then convert once.
• Do not assume a nominal tank volume is the exact liquid volume. Measure usable fill where dosing accuracy matters.
• Do not convert volume to weight without density. A gallon of water and a gallon of oil have different masses; use the density calculator when weight matters.
• Do not confuse the US liquid ladder. In this system, 1 gal = 4 qt = 8 pt = 16 cups, and the same gallon also equals 231 cubic inches.

Sources

• NIST, HB 44 (2024), Appendix C, printed page C-6 (PDF page 6), “Units of Liquid Volume” — 1 US liquid gallon = 231 in³.
• NIST, SP 811 Appendix B.6, “U.S. survey foot and mile” — the international foot is exactly 0.3048 m, hence the inch is exactly 0.0254 m.
• NIST, SI Units — official context for SI units used with metric volume reporting.
• BIPM, SI base units — international SI reference for metric unit definitions.