What this calculator does
Turn US cups into fluid ounces, or fluid ounces into cups, for any recipe. Cups and fluid ounces are both US kitchen units, and they fit together neatly: one cup is exactly 8 US fluid ounces. So converting just means multiplying or dividing by 8. What still trips people up is the word "ounce", which can mean either an amount of space (volume) or a weight.
This page converts cups to fluid ounces, which is volume to volume. It's exact for water, milk, juice, oil or any other liquid. Dry ingredients are often sold by weight in ounces. For those, a cup-to-ounce conversion depends on the ingredient, so there's no single number.
Where it's used
Why this math matters outside the classroom:
- Recipes. A recipe that calls for 12 fl oz of broth needs 1½ cups, since a cup is 8 fl oz.
- Drink sizes. Someone pouring a 20 fl oz bottle of juice into a recipe is adding 2½ cups.
- Weight versus volume. A cup of flour weighs only about 4 to 5 oz, which is why weight ounces and fluid ounces differ.
- Tracking drinks. Someone tracking eight 8 fl oz glasses of water is counting 64 fl oz, which is 8 cups.
- Measuring cups. Students check that the 8 oz line on a liquid measuring cup is the same as the 1 cup line.
Grade level and standards: Grades 4–5; Common Core State Standards for Mathematics 4.MD.A.1, 5.MD.A.1. © Copyright 2010. National Governors Association Center for Best Practices and Council of Chief State School Officers. All rights reserved.
How to use it
- Enter a number of US cups or US fluid ounces.
- Choose cups to fluid ounces, or fluid ounces to cups.
- Read the result and steps. The table shows the common measuring-cup fractions.
What the inputs mean
- Value to convert
- US cups for cups → fl oz, or US fluid ounces for fl oz → cups.
- Direction
- The unit of the number you entered. The table matches it.
Formula and method
US fl oz = cups × 8 cups = US fl oz ÷ 8 1 cup = 236.5882365 mL; 1 US fl oz = 29.5735295625 mL
In the formulas, fl oz means fluid ounces and mL means milliliters. A US gallon holds 128 fluid ounces and 16 cups. So each cup is 128 ÷ 16 = 8 fluid ounces exactly, and both directions are exact.
Behind the scenes, the calculator goes through the metric size of each unit. It lands on the same whole-number ratio of 8.
Worked example
A smoothie recipe needs 2 cups of juice. How many fluid ounces is that?
- 1 cup is exactly 8 US fl oz, so multiply: 2 × 8.
- 2 × 8 = 16 US fl oz.
Result: 2 cups is 16 US fluid ounces, which is also one US pint.
Understanding the result
Handy fractions: ¼ cup = 2 fl oz, ⅓ cup ≈ 2.67 fl oz, ½ cup = 4 fl oz, ¾ cup = 6 fl oz. Going the other way, a 12 fl oz can is 1½ cups and a 20 fl oz bottle is 2½ cups.
Weight vs volume: a cup of water does weigh close to 8 ounces (about 8.3 oz), but most ingredients don't. A cup of flour weighs only about half that, while a cup of honey weighs much more. If a recipe or package lists ounces without "fl", it usually means weight.
Other cups: the metric cup of 250 mL equals about 8.45 US fl oz. The cup used on US nutrition labels (240 mL) is about 8.12 fl oz. Coffee makers often count a "cup" as less than 8 fl oz, so check the manual before comparing.
Assumptions and limitations
- Cups and fluid ounces are standard US kitchen units.
- The conversion is volume to volume.
- It doesn't convert cups to ounces of weight. That needs the ingredient's density (how heavy it is for its size), as in the grams-to-cups calculator.
- Imperial (British) fluid ounces, which are slightly smaller, aren't used.
Frequently asked questions
How many ounces are in a cup?
There are 8 US fluid ounces in a US cup. If you mean ounces of weight, it depends on what's in the cup.
How many cups is 16 ounces?
16 US fl oz is exactly 2 cups (one pint). For 16 ounces by weight, such as a pound of pasta or sugar, the number of cups depends on the ingredient.
Are dry and liquid cups different sizes?
Not in volume. US dry and liquid measuring cups hold the same 8 fl oz. They're shaped differently, so you can level off dry ingredients and read liquids at a marked line.
How this calculator is checked
Method: US customary: 1 gal = 128 fl oz = 16 cups, so 1 cup = 8 fl oz exactly. The calculation is covered by automated tests with known reference values and edge cases. Last updated 2026-10-18. Found a problem? Tell us.
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