How to Convert Ounces to Gallons

Instructor: Maria Airth

Maria has a Doctorate of Education and over 20 years of experience teaching psychology and math related courses at the university level.

This lesson offers step by step instructions for converting U.S. ounces into gallons. You'll also learn how to convert from the Imperial (U.K.) ounce to gallon measurements as well.

Ounces to Gallons

The most important thing to remember about changing ounces to gallons is that there are 128 ounces in every gallon.

ounces to gallons

Another way to think of it is 'for every 128 ounces you have 1 gallon'. This leads directly into the formula: xounces/128 = y gallons (notice this formula divides the number of ounces into groups of 128 to determine the number of gallons).

Let's try an example: A farmer measures his cows' milk production by the ounce but sells it by the gallon. If the farmer collected 19,200 ounces of milk in a week, how many gallons of milk will he be able to sell?

Step 1:

Remember the formula.

  • x ounces/128 = y gallons

Step 2:

Substitute known values into the formula. Here the number of ounces is 19200.

  • 19200/128 = y gallons

Step 3:

Calculate the answer.

  • 150 = y gallons

The equivalent number of gallons is 150. It is most appropriate to answer word problems with full sentences, so the answer to this problem is best written as 'The farmer will be able to sell 150 gallons of milk this week'. Remember that ounces can be abbreviated as oz and gallons can be abbreviated as gal in your answers.


19,200 ounces converts to 150 gallons.

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