Gallons to Forties Converter

Convert beer volume measurements from gallons to forties (40 oz bottles) quickly and accurately. Enter any gallon value and get the equivalent number of 40-ounce bottles, a popular large-format beer container.

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Common Gallons to Forties Conversions

Gallons Forties (40 oz)
0.5 gallon1.6 forties
1 gallon3.2 forties
2 gallons6.4 forties
5 gallons16 forties
7.75 gallons (quarter barrel)24.8 forties
10 gallons32 forties
15.5 gallons (half barrel)49.6 forties
20 gallons64 forties
31 gallons (full barrel)99.2 forties
50 gallons160 forties

How to Convert Gallons to Forties

Converting gallons to forties is useful when working with the iconic 40-ounce beer bottle format. The "forty" has become a cultural staple, particularly for malt liquors and certain beer brands, offering a generous single-serve portion.

The Conversion Formula

The formula to convert gallons to forties is:

forties = gallons x 128 / 40

This formula works because one US gallon contains 128 fluid ounces, and a forty holds 40 fluid ounces. Simplified, this gives us exactly 3.2 forties per gallon.

Example 1: Converting 5 Gallons to Forties

forties = 5 x 128 / 40 = 640 / 40 = 16 forties

A 5-gallon batch equals exactly 16 forty-ounce bottles.

Example 2: Converting 15.5 Gallons to Forties

forties = 15.5 x 128 / 40 = 1984 / 40 = 49.6 forties

A half-barrel keg is equivalent to about 50 forties.

What Is a Forty?

A "forty" is a beer bottle that holds 40 fluid ounces (approximately 1.18 liters). Key facts about forties:

What Is a Gallon?

The US gallon is a unit of volume equal to 128 US fluid ounces or about 3.785 liters. In the context of beer:

Comparison with Other Bottle Sizes

See how forties compare to other common beer containers:

The Cultural Significance of Forties

The 40-ounce bottle holds a unique place in American culture:

Applications of This Conversion

Retail Comparison: When comparing prices between different beer formats, converting to forties can help determine the best value for larger format purchases.

Event Planning: For casual gatherings where forties might be the format of choice, knowing how many you can get from a larger volume helps with bulk purchasing decisions.

Homebrewing: While not a common bottling format for homebrewers, understanding the forty conversion helps visualize batch sizes in familiar terms.

Inventory Management: Stores selling forties can use this conversion to understand how their inventory relates to keg or case quantities.