How Many Ounces In a Gallon? “ All You Need To Know

How Many Ounces In a Gallon? “ All You Need To Know

Are you aware of how many ounces in a gallon of water?

Don?t you know the answer? Or still not sure?

Well, there are different measurement units in various things. So, we would need to know the density of the substance before we could answer the question.

Generally, one important thing to remember about convert ounces to gallons is that there are 128 ounces in each gallon.


  • A gallon is a unit of volume measurement in the US customary and imperial systems, abbreviated as ?gal?.
  • A fluid ounce is a unit of volume in the US customary and imperial systems of measurement abbreviated as ?fl. Oz?. A small quantity or portion.


1350?1400; Middle English unce < Middle French < Latin uncia twelfth part, inch, ounce, a derivative of, (Courtesy:

An important thing is to be noted that fluid ounces and weight ounces are not similar. Liquid ounce measurement indicates the volume of the liquid, while dry ounce measurement records the weight.

But the confusion is not over. There is a total of three players in this game

  • 1 Gallon (Fluid, US) = 128 Ounces (Fluid, US)
  • 1 Gallon (Dry, US) = 148.94684 Ounces (Fluid, US)
  • 1 Gallon (UK) = 160 Ounces (UK)

How many ounces in a gallon?

While using an intermediate unit for an easy conversion by using the equivalence method. We?ll use grams as it?s a smaller and prior unit to both the quantities.

Before we go ahead, lets first clear out the number of grams in terms of ounces and gallons.

Ounces in grams

An ounce is a very small quantity. Mainly for the number of sensitive things like liquid medicine or chemicals.

Like one should be used in drinks. And coming to grams, it is equivalent to an exact 28.3495 grams. Little long fractional unit but exact to the value.

Gallons in grams

One gallon is a large unit for grams, even more than 3 times as bigger as a kilogram. One gallon seems mostly equal to 3.785 kg or more accurately it is equal to 3785.41179 gms. Another big fractional number it is.

So how many ounces in a gallon?

Now we are very clear and already know the full numbers of grams in an ounce and a gallon.

You have finite numbers and we just have to convert it from one unit to the other using the unitary way. The easiest method. It is easy, isn?t it?

So, total grams in one oz is 28.3495. and in one gallon is 3785.41179. Hence the total amount of ounces in a gallon will be equal to 3785.41179 divided by 28.3495 gives us 133.52658. And it is the sure figure of the number of ounces in a single gallon.

So, how many ounces in a gallon? 133.52658 (up to 5 decimal places exact)

Now let?s see how many fluid ounces in one gallon

Still little tricky as here we have fluid ounces. Both two are not the same. As one oz is equal to 28.3495 gms. While fluid ounce is equivalent to 29.57353 gms.

The relation in between number and conversion units, with a fraction of 1/1000 or 0.001 becomes 1 when used with bigger conversions like 1000.

The amount of fluid ounces in a gallon is equal to 3785.41179 gms divided by 29.57353 gms gives us a total of 127.999998 oz. Means a simple 128 oz.

How to calculate differences in an easy way?

Let?s find out?

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One gallon contains 4 quarts, which is also equivalent to 8 pints or 16 cups of liquid. Now we know there is 128 oz in one-gallon means 16 cups is equal to one gallon. A cup is 8 oz. So, there are 128 ounces in a gallon of water.

Originally published at on September 1, 2019.


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