Gallon Calculator · Gallons, Liters, Quarts & Volume Converter

Gallon Calculator

Convert gallons to liters, quarts, pints, cups and more, plus a tank volume helper

Conversion units
Default conversion is US gallon → liter: 1 gal (US) = 3.785411784 L. Toggle to Imperial gallons from the From / To dropdowns.
Amount to convert
gal
L
A US gallon is 231 cubic inches. An Imperial gallon is 4.54609 L — about 20% larger than a US gallon.
Tank / container volume (optional)
ft
ft
gal
Enter the tank's inside dimensions. For a cylindrical tank, the "Length" field is the diameter and "Width" is ignored. Use Use this volume to push the result into the main converter.
Gallon Conversion Result
💧 Small volume
Converted value
—
—
From — To —
US gallons
—
Liters
—
Quarts (US)
—
Pints (US)
—
Cups (US)
—
Fluid ounces (US)
—
Milliliters
—
Imperial gallons
—
Full breakdown — the volume in every unit
UnitValueUnitValue
Common conversions from US gallons
US gallonsLitersQuarts (US)Fluid ounces (US)
Exact US conversions: 1 gal = 4 qt = 8 pt = 16 cups = 128 fl oz = 3.785411784 L. Imperial: 1 imp gal = 4.54609 L = 160 imp fl oz.
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Faiq Ur Rahman

Founder & CEO, Toolraxy

Faiq Ur Rahman is a web designer, digital product developer, and founder of Toolraxy, a growing platform of web-based calculators and utility tools. He specializes in building structured, user-friendly tools focused on health, finance, productivity, and everyday problem-solving.

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Gallons show up everywhere. A 5-gallon bucket. A 55-gallon drum. A 40-gallon water heater. But recipes, fuel stations, and aquariums often speak in liters, quarts, or milliliters. This gallon calculator bridges those units. It converts US gallons, Imperial gallons, liters, quarts, pints, cups, fluid ounces, milliliters, cubic feet, cubic inches, cubic yards, barrels, CCF, acre-feet, and more. Twenty-three units in total. The tank helper adds another layer. Enter inside dimensions for a rectangular or cylindrical tank and get volume in US gallons. Then push that number into the main converter with one click.

 

How to Use the Gallon Calculator

  1. Pick a from unit. Default is US gallon.

  2. Pick a to unit. Default is liter.

  3. Type the amount.

  4. Read the converted value.

  5. Use Swap units to reverse the conversion.

  6. Optional: enter tank dimensions to calculate volume in US gallons.

  7. Click Use this volume to transfer the tank result into the main converter.

  8. Check the breakdown table for the same volume in every supported unit.

 

How the Gallon Calculator Formula Works

Formula: Converted value = amount × (from unit factor ÷ to unit factor)
Formula: 1 US gallon = 3.785411784 liters = 4 quarts = 8 pints = 16 cups = 128 fluid ounces
Formula: 1 Imperial gallon = 4.54609 liters = 1.2009499255 US gallons
Formula: Tank volume (rectangular) = length × width × height
Formula: Tank volume (cylindrical) = π × (diameter ÷ 2)² × height
Formula: US gallons from cubic feet = cubic feet × 7.48051948052

Each unit stores a factor that tells the calculator how many US gallons it equals. The tool converts your input to US gallons first, then divides by the target unit’s factor. That keeps the math consistent across all 23 units. The tank helper uses the same gallon factor for its output. For a rectangular tank, volume in cubic feet times 7.48051948052 gives US gallons. For a cylinder, radius is half the diameter. The tool handles both shapes without extra steps.

 

Worked Example

A rectangular tank measures 4.7 feet long, 2.3 feet wide, and 1.9 feet tall. You want to know its volume in gallons, then convert that to liters.

Volume in cubic feet: 4.7 × 2.3 × 1.9 = 20.539 ft³
Volume in US gallons: 20.539 × 7.48051948052 = 153.65 gal
Volume in liters: 153.65 × 3.785411784 = 581.6 L

The badge reads “Medium volume” because 153.65 gallons falls in the 50–500 range. The breakdown table also shows 614.6 quarts, 1,229.2 pints, 2,458.4 cups, 19,667.2 fluid ounces, and 581,600 milliliters. If you needed Imperial gallons, the same tank holds 127.94 Imperial gallons. The tank helper gives you the US gallon figure directly, and one click moves it to the main converter for any other unit.

How Do You Convert Gallons to Liters?

Multiply gallons by 3.785411784. That’s the exact number of liters in one US gallon. For example, 7 gallons equals 26.498 liters. The calculator does this instantly when you pick gallon as the from unit and liter as the to unit. For Imperial gallons, the multiplier is 4.54609. Always check which gallon your recipe or fuel pump uses.

 

What Is the Difference Between US and Imperial Gallons?

A US gallon is 231 cubic inches, or 3.785411784 liters. An Imperial gallon is 4.54609 liters, about 20% larger. The two are not interchangeable. Fuel in the UK is sold by the Imperial gallon, but most other countries use liters. Recipes from the US use US gallons. The calculator lets you pick either from the dropdowns, so there’s no confusion.

 

How Many Quarts in a Gallon?

There are 4 quarts in a US gallon. That also means 8 pints, 16 cups, or 128 fluid ounces. The breakdown table shows all these at once. A quart is 0.25 gallons. If you have 3 quarts, that’s 0.75 gallons, or 2.839 liters. The tool converts in any direction.

 

How Do You Calculate Tank Volume in Gallons?

For a rectangular tank, multiply length by width by height in feet, then multiply by 7.48051948052. For a cylindrical tank, use π × (diameter ÷ 2)² × height in feet, then multiply by the same factor. The tank helper accepts dimensions in feet, inches, yards, meters, or centimeters. It converts to feet first, then to gallons. Enter inside dimensions for the most accurate result.

 

What Is a Gallon Used For?

Gallons measure liquids in the US, UK, and a few other countries. You’ll see them on milk jugs, paint cans, fuel pumps, aquariums, and water heaters. A standard bathtub holds 40 to 60 US gallons. A 5-gallon bucket is a common size for gardening and cleaning. The calculator helps when you need to switch between gallons and liters, quarts, or milliliters.

 

How Many Fluid Ounces in a Gallon?

One US gallon equals 128 US fluid ounces. That’s 16 cups, or 8 pints, or 4 quarts. An Imperial gallon equals 160 Imperial fluid ounces. The two fluid ounces are different sizes, so the count changes with the gallon type. The calculator shows both when you pick the right units.

 

How Do You Convert Gallons to Cubic Feet?

Divide gallons by 7.48051948052. One cubic foot holds 7.48051948052 US gallons. A 55-gallon drum is about 7.35 cubic feet. The breakdown table includes cubic feet, cubic inches, and cubic yards. That’s useful for shipping, storage, or construction.

 

What Is a 5-Gallon Bucket in Liters?

A 5-gallon bucket holds 18.927 liters. The exact figure is 5 × 3.785411784 = 18.92705892 liters. Many hardware stores sell buckets marked in both gallons and liters. The calculator gives you the precise number. It also shows quarts, pints, cups, and fluid ounces for the same volume.

 

How Do You Use the Tank Helper?

Pick the tank shape. For a rectangle, enter length, width, and height. For a cylinder, enter diameter and height (the width field is ignored). Choose the dimension unit. The helper shows volume in US gallons. Click Use this volume and the number moves into the main converter. Then pick any other unit to see the conversion.

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