1 gal = 3.7854 L
Roughly a gallon of milk. Multiply 1 gal by 3.785411784. The result is 3.7854 L.
Fast answers, clean math
Gallons to liters converter
Enter US gallons and get liters instantly. This page also shows the formula so you can sanity-check the result.
Unit converter
Convert US gallons to liters
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Formula
How to convert US gallon to liter (gal → L)
One US gallon equals exactly 3.785411784 liters. This is an exact definition, not an approximation, so the factor never changes.
Formula: liters = US gallons × 3.785411784
To go the other way, multiply by 0.2641720524: US gallons = liters × 0.2641720524.
For example, 1 gal × 3.785411784 = 3.7854 L.
| Us gallon (gal) | Liter (L) |
|---|---|
| 1 gal | 3.7854 L |
| 2 gal | 7.5708 L |
| 3 gal | 11.3562 L |
| 5 gal | 18.9271 L |
| 10 gal | 37.8541 L |
| 15 gal | 56.7812 L |
| 20 gal | 75.7082 L |
| 30 gal | 113.5624 L |
| 50 gal | 189.2706 L |
| 100 gal | 378.5412 L |
Step by step
Worked US gallon to liter examples
5 gal = 18.9271 L
Roughly a water cooler jug. Multiply 5 gal by 3.785411784. The result is 18.9271 L.
15 gal = 56.7812 L
Roughly a car fuel fill. Multiply 15 gal by 3.785411784. The result is 56.7812 L.
Background
What is a US gallon?
A US gallon is a unit of volume defined as exactly 3.785411784 liters, made up of 4 quarts, 8 pints, or 128 US fluid ounces.
The US gallon is based on the old English wine gallon of 231 cubic inches. It is smaller than the imperial gallon used in the United Kingdom, which is about 4.546 liters.
Everyday scale: A US gallon of milk weighs about 8.6 pounds. A typical kitchen sink holds several gallons, and US fuel is sold by the gallon.
System: US customary.
Background
What is a liter?
A liter is a metric unit of volume equal to one cubic decimeter, or 1,000 cubic centimeters (milliliters).
The liter was introduced in France in 1795 and remains the everyday metric volume unit, although the cubic meter is the formal SI unit.
Everyday scale: A liter is a little more than a US quart. A standard large water bottle is often one liter, and a kilogram of water occupies almost exactly one liter.
System: metric (SI).
Where it helps
When you need to convert US gallon to liter
Cooking and recipes
Recipes move between milliliters, liters, cups, and gallons depending on where they were written. Converting keeps liquid ratios correct so sauces, doughs, and drinks turn out as intended.
Fuel and automotive
Fuel economy and tank sizes are quoted in liters or gallons by region. Converting helps you compare prices, estimate range, and budget for a fill-up while traveling.
Home and garden
Paint, cleaning products, aquariums, and watering schedules list capacity in different volume units. Converting helps you buy the right amount and follow dilution instructions safely.
Accuracy
Precision and common mistakes
The US gallon to liter factor is exact by definition, so any error comes from rounding too early. Keep full precision through your calculation and round only the final answer to the precision your task needs.
A common mistake is rounding the conversion factor to two or three digits before multiplying, which can shift the result noticeably on large values. Multiply first, then round. Always keep the unit label with the number so the meaning is never lost.
| Use case | Good rounding |
|---|---|
| Drinks and everyday cooking | Common fractions or 1 decimal place |
| Baking liquids | 2 decimal places |
| Fuel and large containers | 1 decimal place |
| Lab and medical dosing | Use the exact factor, then round at the end |
Plain answers
Us gallon to liter FAQ
How do you convert US gallon to liter?
Multiply the number of US gallons by 3.785411784. That single factor converts any US gallon value to liters.
How many liters are in one US gallon?
One US gallon equals 3.785411784 liters.
What is 5 gal in L?
5 US gallons equals about 18.9271 liters.
Is the US gallon to liter conversion exact?
Yes. The factor is fixed by international definition, so US gallon to liter is an exact conversion rather than an estimate.
How can I estimate US gallon to liter in my head?
Multiply gallons by 3.8, so 5 gallons is about 19 liters.