US liquid gallon to Cubic inch

gal

1 gal

in³

231 in³

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Quick Reference Table (US liquid gallon to Cubic inch)

US liquid gallon (gal)Cubic inch (in³)
0.5115.5
1231
2462
51,155
102,310
5011,550

About US liquid gallon (gal)

The US liquid gallon is a unit of volume equal to 4 quarts, 8 pints, or 128 US fluid ounces, approximately 3.785 liters. It is the primary large liquid volume unit in the United States, used for fuel pricing at the pump, milk and juice packaging, and paint. US fuel economy is measured in miles per gallon (MPG). The US gallon is about 17% smaller than the UK imperial gallon (4.546 L), causing significant differences in fuel economy comparisons.

A gallon jug of milk is 3.785 L. Petrol (gasoline) is priced per US gallon at every US fuel station.

About Cubic inch (in³)

A cubic inch (in³) is the volume of a cube with 1-inch sides, equal to approximately 16.387 milliliters. In the US, it is used for engine displacement (the classic Chevrolet 350 = 350 in³ ≈ 5.7 L), small container volumes, and pharmaceutical packaging. Car engine displacement was historically described in cubic inches before the automotive industry switched to liters in the 1980s–1990s. The unit also appears in 3D printing and medical device specifications.

A classic Chevy 350 V8 engine displaces 350 in³ (≈ 5.7 L). A standard tennis ball has a volume of about 15 in³.


US liquid gallon – Frequently Asked Questions

US fuel infrastructure — pumps, tax law, pipeline contracts, and consumer expectations — is built around the gallon. Federal and state fuel taxes are levied per gallon; EPA fuel economy standards use miles per gallon; and consumers benchmark prices against a gallon reference ("$3 a gallon"). Switching to liters would require reprogramming every pump, rewriting tax code, and re-educating 330 million people who compare prices by the gallon. Canada made the switch in the 1970s during a broader metrication push, but the US never had the political will for a comprehensive changeover.

The US gallon (3.785 L) is based on the Queen Anne wine gallon of 1707 (231 cubic inches). The UK imperial gallon (4.546 L) was defined in 1824 as the volume of 10 pounds of water. The two systems diverged after US independence.

To convert: L/100km = 235.2 ÷ MPG (US). A car achieving 30 MPG uses about 7.8 L/100km. UK MPG values are always higher than US MPG for the same car because the imperial gallon is larger.

Recommended daily water intake is about 2–3 liters (roughly 0.5–0.8 US gallons). The commonly cited "8 glasses a day" ≈ 64 fl oz ≈ 0.5 gallons ≈ 1.9 liters.

Most US passenger cars have fuel tanks of 10–20 gallons (38–76 liters). Compact cars are typically 10–13 gallons; mid-size cars 14–17 gallons; SUVs and trucks 18–36 gallons.

Cubic inch – Frequently Asked Questions

One cubic inch equals approximately 16.387 mL. This follows from 1 inch = 2.54 cm, so 1 in³ = 2.54³ cm³ = 16.387 cm³ = 16.387 mL.

American car engines were historically described in cubic inches of displacement. The 350, 427, and 454 in³ engines are iconic V8 ratings. Most manufacturers switched to liters in the 1980s–1990s, but cubic inches remain part of classic car culture.

One liter equals approximately 61.024 cubic inches. A 350 in³ engine is approximately 5.74 liters.

Cubic inches are still used in the US for motorcycle and small engine displacement, small packaging volumes, and some industrial contexts. 3D printer filament usage is sometimes estimated in cubic inches.

One US fluid ounce equals approximately 1.805 cubic inches. One cubic inch equals about 0.554 US fluid ounces. These conversions are used in packaging design and liquid container manufacturing.

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