Cubic Inches to Gallons Converter
Unit ConversionConvert cubic inches to gallons. 1 cubic inch is about 0.004329 gallons, with a conversion table, worked examples and the reverse conversion.
Gallons
Equivalent volume in gallons
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SponsoredThis converter turns cubic inches into gallons (in3 to gallons). Enter a value and the result updates as you type. The section "How Many Cubic Inches in a Gallon" below gives the factor and where it comes from.
Fuel tanks, aquariums and small containers measured in inches give a volume in cubic inches, and one division turns it into US gallons. A box 12 by 12 by 16 inches, for example, holds 2,304 cubic inches. The US dry gallon (268.8025 cubic inches) and the UK imperial gallon are different units and give different answers.
The result is rounded to 6 decimal places, but the factor behind it never is, so long chains of conversions stay accurate. Type a whole number or a decimal; the conversion table below lists common values.
How Many Cubic Inches in a Gallon
A US gallon is exactly 231 cubic inches. This is the legal definition of the US liquid gallon, given in NIST Handbook 44, and it goes back to the English wine gallon that the American colonists adopted. The quart (57.75 cubic inches) and the pint (28.875 cubic inches) follow from it.
Imperial and Dry Gallons
The British imperial gallon, set in 1824 as the volume of 10 pounds of water, is about 277.42 cubic inches, and the US dry gallon is 268.8025 cubic inches. Some converters answer with one of these by mistake, which is why their numbers differ from 231.
How to Convert Cubic Inches to Gallons
To convert cubic inches to gallons, divide by 231. For example, 350 cubic inches is about 1.515152 gallons.
To go from gallons back to cubic inches, multiply by 231. For example, 5 gallons equals exactly 1,155 cubic inches.
Cubic Inches to Gallons Conversion Table
Common values in cubic inches converted to gallons, rounded to 6 decimal places.
| Cubic Inches | Gallons |
|---|---|
| 1 in³ | 0.004329 gal |
| 10 in³ | 0.04329 gal |
| 57.75 in³ | 0.25 gal |
| 100 in³ | 0.4329 gal |
| 115.5 in³ | 0.5 gal |
| 231 in³ | 1 gal |
| 500 in³ | 2.164502 gal |
| 1,000 in³ | 4.329004 gal |
| 1,155 in³ | 5 gal |
| 2,310 in³ | 10 gal |
| 5,000 in³ | 21.645022 gal |
| 10,000 in³ | 43.290043 gal |
From Tank Size to Gallons
Measure the inside of a rectangular tank in inches, multiply length by width by height, and divide by 231. A tank 20 by 10 by 12 inches holds 2,400 cubic inches, which is about 10.39 gallons. The Aquarium Water Volume Calculator does this for rectangular and cylinder tanks and allows for the gap below the rim, and the Tank Volume Calculator handles cylinders.
Frequently Asked Questions
How many gallons is 50 cubic inches?
About 0.21645 gallons.
How many gallons is 150 cubic inches?
About 0.649351 gallons.
How many gallons is 200 cubic inches?
About 0.865801 gallons.
How many gallons is 300 cubic inches?
About 1.2987 gallons.
How many gallons is a 350 cubic inch engine?
350 cubic inches is about 1.5152 gallons, the same space as about 5.74 liters. Engine size is a swept volume, not a fuel capacity, so it is usually quoted in liters or cubic inches rather than gallons.
What happens if I enter a negative number?
The result shows a dash. A volume is an amount of space, so it is never below zero; a minus sign in front of a value is usually a typing slip.
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