Gallons to Liters Converter

The gallons to liters converter is a fast, exact-volume conversion tool that moves any reading between gallons (gal) and liters (L) in both directions, using the exact NIST Handbook 44 reference for the US liquid gallon (1 US gal = 3.785411784 L exactly) or the Imperial Units Act 1824 / Weights and Measures Act 1985 reference for the UK imperial gallon (1 UK gal = 4.54609 L exactly). Type a number into either field and the other updates live, with no rounding ambiguity and no measurement uncertainty, because the relationship between each gallon and the liter is fixed by international definition rather than measured. It is built for the everyday situations where you are handed a volume figure in one system and need the other immediately: an American recipe that calls for a half gallon of milk but your measuring jug is in liters; a UK supermarket label that quotes 4.546 L per bottle but the comparison price is in US gallons; a North American fuel-economy chart that states 264.172 US gallons per cubic meter but a fuel-ordering form that asks for liters per tonne; an engineering printout that prints a tank capacity as 750 US gallons while the commissioning documentation quotes the same capacity as 2839.06 L (to the nearest 0.01); or a scientific paper that uses UK imperial gallons for an older experimental protocol while the modern supplementary data is in liters and milliliters. The page includes bonus read-outs for milliliters, cubic meters, US fluid ounces, and the other gallon alongside the primary gal ⇄ L result, and a toggle that switches between the US gallon (the modern, NIST-referenced definition used in roughly 75 % of the world's volume documentation) and the UK imperial gallon (the older British definition that survives on British supermarket labels, brewing recipes, and Commonwealth chemical-handling notes).

The converter assumes the US liquid gallon by default. That gallon, sometimes called the "wine gallon" because of its early association with the wine trade, has been exactly 231 cubic inches, and therefore exactly 3.785411784 liters, since the United States adopted the relationship in the nineteenth century and codified it in 1 CFR §51 BSP-Sec. 4.51 Appendix B (Weights and Measures Division of the National Bureau of Standards, codified into federal law). NIST Handbook 44 ("Specifications, Tolerances, and Other Technical Requirements for Weighing and Measuring Devices"), the official reference for retail trade in the United States, cites the same constant for trade-legal gallon capacity. The US gallon survives as the standard volume unit for retail gasoline, milk, paint, and bottled water in the United States, Liberia, and Myanmar, and is the working unit for fuel-economy ratings, aircraft fuel orders, and most US-bound international shipping manifests. For UK domestic volumes (milk in pints, beer in pints, petrol in litres, but bottled cider and wine in 75 cL or 70 cL bottles), the relevant gallon is the imperial UK gallon, which has been exactly 4.54609 liters since 1824. The toggle at the top of the page switches the conversion factor without losing what you have already typed.

How to use this converter

1. Type the numeric value you want to convert into the Gallons (US) or Gallons (UK) field, depending on which gallon your source data uses. Decimal values are accepted, including sub-gallon values such as 0.5 US gal (≈ 1.893 L) and sub-liter values such as 0.001 L (≈ 2.6417 × 10⁻⁴ US gal = 0.000264 US gal).
2. For the Gallons To Liters, The opposite field updates automatically as you type. For the Gallons To Liters, The update is recomputed on every keystroke, so the panel always reflects the latest value.
3. Read the Result in gallons (US/UK) row to see the same volume quoted in your chosen gallon definition, and the Result in liters row to see it in SI volume units.
4. Read the Also in milliliters, Also in cubic meters, Also in US fluid ounces, and Also in [other] gallons rows for the four most common cross-unit read-outs at the same time. These bonus rows are all computed against the variant you have selected, except the cross-gallon row, which always shows the other gallon.
5. Use the toggle at the top to switch between US (3.785411784 L) and UK (4.54609 L). The gallon reading re-derives from the current input under the new factor, so you can flip between definitions without retyping.
6. Use the ⇄ swap button when you want to flip the orientation: the value in the liters field moves to the gallons field and vice versa.
7. Click Copy gal or Copy L to put the value on the clipboard in your chosen unit.
8. To convert a recipe, fuel quantity, or other volume, enter the value in either field and read the result.

the Gallons To Liters runs entirely in the browser. For the Gallons To Liters, Inputs are not stored, not transmitted, and not associated with any account.

The Formulas

The conversion between each gallon and liters is defined rather than measured, so there are exact factors for each gallon definition:

US liquid gallon (NIST Handbook 44, 1 CFR §51 BSP-Sec. 4.51 Appendix B):

1 US gal = 3.785411784 L exactly

To convert US gal → L: multiply by 3.785411784.

L = US gal × 3.785411784

To convert L → US gal: divide by 3.785411784.

US gal = L / 3.785411784

UK (imperial) gallon (Imperial Units Act 1824; Weights and Measures Act 1985):

1 UK gal = 4.54609 L exactly

To convert UK gal → L: multiply by 4.54609.

L = UK gal × 4.54609

To convert L → UK gal: divide by 4.54609.

UK gal = L / 4.54609

Between the two gallon definitions:

1 US gal = 3.785411784 / 4.54609 = 0.83267384 UK gal (the US gallon is about 16.73% smaller than the UK gallon)

1 UK gal = 4.54609 / 3.785411784 = 1.2009499255... US gal (the UK gallon is about 20.09% larger than the US gallon)

Bonus read-outs (US gallon as the reference, unless UK variant is selected):

1 US gal = 3785.411784 mL (since 1 L = 1000 mL exactly) 1 US gal = 0.003785411784 m³ (since 1 m³ = 1000 L exactly) 1 US gal = 128 fl oz (US) (since 1 US gal = 4 quarts and 1 quart = 32 fl oz) 1 US gal = 0.83267384 UK gal (the cross-gallon read-out)

1 UK gal = 4546.09 mL (exact) 1 UK gal = 0.00454609 m³ (exact) 1 UK gal = 160 fl oz (UK) (exact) 1 UK gal = 1.2009499255... US gal (the cross-gallon read-out)

1 L = 1000 mL (exact) 1 L = 0.001 m³ (exact) 1 L = 33.8140227... fl oz (US) 1 L = 35.1950797... fl oz (UK)

Two gallons, two histories

The reason there are two "gallons" is the separate evolution of British and American customary units after the United States became independent in 1776. The British had been using a "wine gallon" of 231 cubic inches since the late seventeenth century and an "ale gallon" of 282 cubic inches at the same time. Both were ultimately displaced by the imperial gallon in 1824, when the Imperial Units Act redefined British liquid measure against the volume of 10 pounds of distilled water at standard temperature and pressure. That gave 1 imperial gallon = 4.54609 L exactly. The United States kept the older Queen Anne wine gallon of 231 cubic inches (≈ 3.785411784 L) as its base unit for liquid measure, which became the legal US gallon under the 1832 Treasury decision and was later codified into NIST Handbook 44. As a result, a UK gallon is about 20 % larger than a US gallon, and a UK pint (568.261 mL) is correspondingly about 20 % larger than a US liquid pint (473.176 mL). The two gallons never reconciled; modern international trade documents generally specify which gallon is meant, and adapters are explicit.

Where the conversion matters

The gallon-to-liter conversion touches far more domains than casual cooking and fuel-economy comparisons. Industrial chemistry formulates aqueous solutions in liters and cubic meters but quotation documents still quote per-gallon prices for some commodity chemicals (especially in the United States). Automotive fuel-economy standards vary by jurisdiction: the United States Environmental Protection Agency (EPA) reports miles per US gallon, the United Kingdom Department for Transport reports miles per UK gallon, and the European Union plus most of the rest of the world uses liters per 100 kilometers. Aviation fuel orders specify in US gallons for international cargo flights, but a UK-based operator converting a fuel-into-plane estimate must multiply by 4.54609 / 3.785411784 ≈ 1.2009499255 to reconcile the two. Homebrewing and craft beer recipes are written in either US gallons or UK gallons depending on the original source, and using the wrong gallon for a 5-gallon recipe is enough to ruin a batch, the conversion is the only safeguard. Pharmaceutical compounding uses milliliters, but older British pharmacopoeias (BP) gave some doses in UK fluid ounces (28.4131 mL), while older US pharmacopoeias gave the same doses in US fluid ounces (29.5735 mL); the small per-ounce difference compounds over multi-ounce doses. Public works and water-mains engineering talk about liters per second for new construction but gallons per minute for legacy pump curves; the conversion is the same in both cases. The bonus-row design of this page lets you read all of these, milliliters, cubic meters, US fluid ounces, and the other gallon, without leaving the page.

Worked examples

Example 1: Convert 5 US gallons to liters.

L = 5 × 3.785411784 = 18.92705892 L exactly.

In mL: 5 × 3785.411784 = 18 927.05892 mL. In cubic meters: 5 × 0.003785411784 = 0.01892705892 m³. In US fluid ounces: 5 × 128 = 640 fl oz. In UK gallons: 5 × 0.83267384 = 4.16336920 UK gal.

Example 2: Convert 4.54609 L (one UK gallon) to US gallons.

US gal = 4.54609 / 3.785411784 = 1.2009499255... US gal exactly (modulo display rounding).

In mL: 4 546.09 mL. In cubic meters: 0.00454609 m³. In US fluid ounces: 4.54609 × 33.8140227 = 153.7219... fl oz. In UK gallons: 4.54609 / 4.54609 = 1 UK gal exactly.

Example 3: A 55-US-gallon oil drum converted to liters.

L = 55 × 3.785411784 = 208.19764812 L exactly.

That is the familiar "55-gallon drum" of petroleum engineering, the same drum holds 45.7970612 UK gallons if you read it on a UK gauge.

Example 4: A car's 12-UK-gallon petrol tank in liters.

L = 12 × 4.54609 = 54.55308 L exactly.

In US gallons: 12 × 1.2009499255 = 14.411399106 US gal. So a car advertised in the UK as having a "12 gallon tank" holds 54.55 L, but the same tank, read on a US fuel-station rating, would read 14.41 US gallons.

Tips for accurate conversion

• Be explicit about which gallon. US and UK gallons differ by about 20 %. A UK "5-gallon" cask holds 22.73 L, not 18.93 L. Documents that quote gallons without qualification in an international context are an immediate red flag.
• Use the exact factor at every step. Round-trip errors pile up: rounding 18.93 L to 18.9 L and back loses 0.03 L over a single conversion. With the exact 3.785411784 factor, the round trip is identity.
• Beware the US dry gallon. A separate "dry gallon" of exactly 4.40488377086 L exists for measuring dry commodities such as grain and fruit. This converter covers the liquid gallon only; never use it for US dry measure unless the label explicitly states "dry gallon".
• Quote the conversion, not just the answer. Writing "5 US gal ≈ 18.93 L" lets the next reader see exactly which gallon is in play; "5 gal ≈ 18.93 L" silently assumes the reader knows which gallon.
• For cooking, prefer mass over volume for flour and sugar. A US gallon of sifted all-purpose flour weighs about 1.6 kg, but packing density changes that figure significantly. Volume conversions are most reliable for liquids.
• For fuel-economy work, do the math in SI. Compute the fuel consumption in liters per 100 kilometers and the fuel amount in liters; convert to the relevant gallon only for the final display. This avoids stacking two approximations.

Frequently Asked Questions

How many liters are in a US gallon exactly? There are exactly 3.785411784 liters in one US liquid gallon. This is not an approximation or a measurement, it is the legal definition, derived from the US gallon being exactly 231 cubic inches and the inch being exactly 2.54 centimetres. NIST Handbook 44 and the United States federal regulation 1 CFR §51 BSP-Sec. 4.51 Appendix B both cite the same figure, and the constant does not have measurement uncertainty attached to it.

How many liters are in a UK gallon exactly? There are exactly 4.54609 liters in one UK imperial gallon. This comes from the Imperial Units Act 1824 (and its successor, the Weights and Measures Act 1985), which defined the imperial gallon as the volume of ten pounds of distilled water at standard temperature and pressure. The conversion to liters is exact under the modern SI definition of the kilogram and the metre, so 1 UK gal = 4.54609 L is also an exact, definitionally pinned constant.

How much bigger is a UK gallon than a US gallon? A UK gallon is about 20.09 % larger than a US gallon. The exact ratio is 4.54609 / 3.785411784 = 1.2009499255..., meaning that one UK gallon equals 1.2009499255 US gallons. The reciprocal, 0.83267384, is the fraction of a UK gallon that one US gallon represents. The difference matters: a 5-US-gallon recipe is 18.927 L, but a 5-UK-gallon recipe is 22.730 L, an extra 3.8 litres, or almost four extra cans of soda's worth.

How many US fluid ounces are in a US gallon? There are exactly 128 US fluid ounces in one US liquid gallon. This breaks down as 1 gallon = 4 quarts = 8 pints = 16 cups = 32 gills = 128 fluid ounces. The US fluid ounce itself is exactly 29.5735295625 mL, so the chain of definitions is consistent: 128 × 29.5735295625 = 3785.411784 mL, which is exactly 3.785411784 L. (Note: the UK fluid ounce is a different unit at exactly 28.4130625 mL, and a UK gallon contains 160 of those, not 128.)

How do I convert liters to US gallons? Divide by 3.785411784. So 1 L = 0.2641720523... US gal, 4 L = 1.0566882094 US gal, 10 L = 2.6417205234 US gal, and 100 L = 26.4172052344 US gal. The calculator on this page works in either direction and shows nine decimal places by default so that round-trip conversions (US gal → L → US gal) return the original number bit-for-bit, modulo the precision of the input.

Which gallon is used at the gas station in the United States? US gas stations dispense in US liquid gallons. The fuel-economy sticker on a US-market car is in miles per US gallon (mpg), and the EPA fuel-economy tests measure against the same unit. If you cross into Canada or Mexico, the same gallon (3.785411784 L) applies in Canada, while Mexico switched to liters at the pump in the 1990s, a US gallon of fuel in Mexico is labeled 3.785 L (rounded to three decimals).

Which gallon is used in the United Kingdom at the supermarket? UK supermarket labels are in liters and milliliters since metrication in the 1970s and 1980s. Beer and cider served in pubs are still dispensed in UK pints (568.261 mL = 1/8 of a UK gallon) under a 1988 European exemption. Petrol (gasoline) at UK filling stations is sold in liters. The UK gallon therefore survives mainly on some brewing sheets, in aviation fuel orders, and on occasional vintage recipes and chemical-handling notes, so when a UK source says "gallon" without qualification, the imperial gallon is the correct interpretation.

What is a dry gallon and does this converter apply? The US dry gallon is a separate unit of volume equal to exactly 4.40488377086 L, used historically for measuring dry commodities such as grain, fruit, and other agricultural produce. It is rarely encountered in modern commerce, bulk grain is usually weighed, not measured in dry gallons, and this converter covers the liquid gallon only. If your problem involves the dry gallon (also written "dry gal" or sometimes "gallon (dry)"), use a dry-volume converter instead.

How accurate is the conversion at high precision? The conversion factors are exact, not approximate. 1 US gal = 3.785411784 L and 1 UK gal = 4.54609 L are both exact identities under the international definitions of the inch, the pound, and the litre. Round-trip conversions (e.g. 5 US gal → L → US gal) are identity at full precision. Rounding to a smaller number of decimals is the only source of error, which is why this calculator shows nine decimal places by default. Use full precision whenever the conversion matters for invoicing, compliance, or scientific reporting.

Why do some recipes use cups and tablespoons instead of gallons? Cups and tablespoons are finer-grained units that allow a single recipe to scale across serving sizes without switching unit systems. They are also unaffected by the US-vs-UK gallon distinction, since a US cup (236.588 mL) and a UK cup (250 mL) differ by only 5.66 %, far less than the 20 % gap between US and UK gallons. For a recipe that needs precision, the working units are milliliters (universal) or cups (US-only); gallons are reserved for large batches, catering quantities, and bulk beverage orders.

Can I convert between cubic meters and gallons using this calculator? Yes, indirectly. Read off the Result in liters row, divide by 1000 to get cubic meters, and you have a clean conversion. The dedicated Also in cubic meters (m³) bonus row does that multiplication for you automatically: 1 US gal = 0.003785411784 m³ exactly, and 1 UK gal = 0.00454609 m³ exactly. For larger volumes, swimming pools, reservoir capacity, residential water meters, express the value in cubic meters and use the round m³ number directly.

Also try these free tools:

• Volume Converter
• Liters to Cubic Meters Converter
• Cups to Milliliters Converter
• Fluid Ounces to Milliliters Converter