How Many Ounces in a Gallon? (Plus: How Many Cups in a Quart)

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Understanding basic kitchen and liquid measurements is more useful than most people realize. Whether you’re following a recipe, tracking your daily water intake, or working on a DIY project, knowing how many ounces, cups, quarts, or gallons you’re dealing with can save time and prevent mistakes. Two of the most common questions people search for are “How many ounces are in a gallon?” and “How many cups are in a quart?” — and today we’ll answer both clearly.

How Many Ounces Are in a Gallon?

A gallon is a large unit used mainly for measuring liquids. In the United States, the standard US liquid gallon contains:

✔️ 128 fluid ounces

This is why so many hydration goals refer to “drinking 64 ounces a day” — that’s half a gallon.

Here’s a quick breakdown of the conversion:

Measurement Fluid Ounces

1 cup 8 fl oz

1 pint 16 fl oz

1 quart 32 fl oz

1 gallon 128 fl oz

So, if you ever need to convert gallons to ounces or vice-versa, just remember:

1 gallon = 128 ounces

1 ounce = 0.0078125 gallons

How Many Cups Are in a Quart?

Another popular measurement question is the relationship between cups and quarts, especially in cooking and baking.

✔️ 1 quart contains 4 cups

This is easy to remember because each quart is exactly four times the size of a cup.

Here’s a quick chart:

Measurement Cups

1 cup 1

1 pint 2

1 quart 4

1 gallon 16

Since 1 gallon equals 4 quarts, you can scale up quickly:

4 cups = 1 quart

16 cups = 1 gallon

US vs. UK (Imperial) Differences

While the US gallon is 128 ounces, the UK Imperial gallon is bigger and equals 160 ounces.

Similarly, Imperial quarts and cups differ slightly as well.

If you’re following an online recipe, always check whether it’s using US or Imperial measurements to avoid mistakes.

Quick Memory Trick

Here’s a classic visual trick that helps many people remember conversions:

G = Gallon

Inside it are 4 Qs = Quarts

Each Q contains 2 Ps = Pints

Each P contains 2 Cs = Cups

Since each cup is 8 ounces, this helps you scale everything up mentally.

Final Thoughts

Knowing how many ounces are in a gallon — and how many cups are in a quart — makes cooking, measuring liquids, and following instructions much easier. Now you know:

1 gallon = 128 ounces

1 quart = 4 cups

Simple, clear, and easy to use anytime you need a quick conversion.