Gallons to Liters Calculator
Ever tried following a British recipe only to end up with way too much liquid? Or puzzled over why your American car manual's fuel tank capacity doesn't match what you see at European gas stations? The culprit is usually a gallon conversion gone wrong.
This calculator handles the conversion both ways—gallons to liters and liters to gallons—with one crucial feature most converters skip: you can choose between US gallons and Imperial gallons. That distinction matters. An Imperial gallon is nearly 20% larger than a US gallon, so using the wrong one can seriously throw off your results.
Enter your number, pick your gallon type, and get your answer instantly.
How to Use This Calculator
1. Pick your direction. Converting gallons to liters? Select that option. Going the other way? Choose "Liters to Gallons."
2. Type in your number. Decimals work fine—enter 2.5, 0.75, whatever you need.
3. Select US or Imperial gallon. Not sure which one? Keep reading—there's a whole section on this below.
4. Get your result. It updates the moment you enter your values. No buttons to click, no waiting.
How Many Liters in a Gallon?
Straight answer:
- 1 US gallon = 3.79 liters
- 1 Imperial gallon = 4.55 liters
If you're in the United States or using anything American—recipes, car specs, product labels—you need the US gallon number. That's 3.79 liters, or about four 1-liter bottles minus a small glass.
US Gallon vs Imperial Gallon: Why This Actually Matters
Here's where people get tripped up: there are two different gallons, and they're not even close to the same size.
The US gallon holds 3.785 liters. Every gas pump, milk jug, and paint can in America uses this measurement. It's been this way since the country was founded—the US simply kept the English wine gallon that colonists were already using.
The Imperial gallon holds 4.546 liters—about 20% more. Britain created this "new and improved" gallon in 1824, standardizing it as exactly 10 pounds of water. The thing is, the US had already been independent for nearly 50 years by then, so Americans never adopted the change.
This means a "gallon" in a 1960s British cookbook is genuinely a different amount than a "gallon" in an American one. Get this wrong and your recipe is off by a fifth.
Quick Guide: Which Gallon Do You Need?
Your source is... | Use this |
|---|---|
Anything American | US Gallon |
British (especially pre-1970) | Imperial Gallon |
Modern UK (fuel, beer) | Often still Imperial—check context |
Canadian | Tricky—officially metric now, but older refs are Imperial |
Australian/NZ older books | Imperial Gallon |
When in doubt: If it's American, it's US gallons. If it's British and more than a few decades old, it's probably Imperial. Modern international sources typically just use liters to avoid this whole mess.
The Conversion Formulas
For those who want to do the math themselves:
US Gallons
- To liters: Multiply gallons by 3.785
- To gallons: Divide liters by 3.785
Imperial Gallons
- To liters: Multiply gallons by 4.546
- To gallons: Divide liters by 4.546
Mental Math Shortcuts
No calculator handy? These get you close enough for everyday situations:
- US gallons → liters: Multiply by 4, then subtract a little (you'll be within 6%)
- Liters → US gallons: Divide by 4, then add a little back
- Imperial gallons → liters: Just multiply by 4.5
Good enough for eyeballing recipe adjustments or estimating fuel needs.
Quick Reference Tables
US Gallons to Liters
US Gallons | Liters |
|---|---|
½ | 1.89 |
1 | 3.79 |
2 | 7.57 |
3 | 11.36 |
5 | 18.93 |
10 | 37.85 |
15 | 56.78 |
20 | 75.71 |
50 | 189.27 |
100 | 378.54 |
Imperial Gallons to Liters
Imperial Gallons | Liters |
|---|---|
½ | 2.27 |
1 | 4.55 |
2 | 9.09 |
5 | 22.73 |
10 | 45.46 |
Real-World Examples
Cooking a Big Batch
Your aunt's famous punch recipe calls for 2 gallons of ginger ale. You're at a European grocery store staring at liter bottles.
The math: 2 US gallons = 7.57 liters. Grab four 2-liter bottles—that gives you 8 liters, slightly more than you need. Close enough, and you'll have a bit extra.
Renting a Car Abroad
You're picking up a rental in Germany. The specs say 50-liter fuel tank. How does that compare to your car back home?
The math: 50 liters ÷ 3.785 = 13.2 US gallons. That's a bit smaller than a typical American sedan (usually 14-16 gallons), so plan your fuel stops accordingly.
Painting the Deck
The stain you want covers 400 square feet per gallon. Your deck is 1,200 square feet, so you need 3 gallons. But the local hardware store only has metric sizes.
The math: 3 US gallons = 11.36 liters. A 10-liter can won't quite cover it. You'd need either 12 liters or three 4-liter cans to be safe.
Setting Up an Aquarium
You bought a 75-gallon tank in the US, but the plant fertilizer instructions are all in metric—"add 5ml per 40 liters."
The math: 75 US gallons = 283.9 liters. Round to 280 liters for easy math. That's 7 doses of 40 liters each, so you'd add 35ml of fertilizer.
Understanding Soda Bottle Sizes
How many 2-liter bottles of soda equal a gallon?
The math: 1 US gallon = 3.79 liters. So you'd need just under two 2-liter bottles (1.89 bottles, to be exact). Grab two bottles and you've got a bit more than a gallon.
Tips for Getting Conversions Right
Identify your gallon type first. This is the most common source of errors. American source? US gallon. British cookbook from your grandmother? Probably Imperial. Modern international specs? They usually just give you liters.
Match your precision to your task. Making soup? Rounding to 3.8 liters per gallon is fine. Mixing chemicals for a pool? Use the full precision (3.785) and double-check your math.
Trust but verify for anything important. If you're calculating medication doses for an aquarium or mixing anything where accuracy affects safety, run the conversion twice or check it against another source.
Remember the 20% rule. If something seems off by about a fifth, you might have used the wrong gallon type. That's often enough of a clue to catch the mistake.
About These Conversions
The values used in this calculator are the exact, internationally defined standards:
- 1 US gallon = 3.785411784 liters (defined by the US National Institute of Standards and Technology)
- 1 Imperial gallon = 4.54609 liters (defined by the UK Weights and Measures Act)
For everyday purposes, 3.79 and 4.55 work perfectly. The extra decimal places only matter in laboratory or industrial settings where tiny differences compound across large quantities.