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US cups to US fluid ounces converter

Convert US cups to US fluid ounces (cups to oz) with the exact factor, a conversion chart and worked steps.

Drafted with AI writing toolsUpdated Checked examples: 3

cup
Try
US fluid ounces
fl oz
US fluid ounces: 16 fl oz
Significant figures: 12; Nearest, ties away from zero
Conversion
2 cup = 16 fl oz
1 fl oz in US cups
0.125cup

2 cup is about 16 fl oz. In the other direction, 1 fl oz ≈ 0.125 cup.

US cups to US fluid ounces

02040602468cupfl oz2 → 16
Cups to oz chart Rows: 10
US cupsUS fluid ounces
0.252
0.54
0.756
18
1.512
216
324
432
648
864
How it's calculated S

  1. Conversion factor

    1 cup=8 fl oz1\ \text{cup} = 8\ \text{fl oz}

    Exact by definition.

  2. Multiply

    2×8=16 fl oz2 \times 8 = 16\ \text{fl oz}

About the US cups to US fluid ounces converter

To convert US cups to US fluid ounces, multiply by 8; to convert back, multiply by 0.125. For example, 2 cup is about 16 fl oz. Displayed factors and results may be rounded.

A recipe written in US cups may need conversion for a graduated jug or a set of measuring spoons. Fractions such as a quarter or three quarters of a cup are valid inputs. This is a US customary cup; a metric cup uses a different capacity.

For the US customary cup, 1 US cup = 8 US fl oz = 236.5882365 mL. These values are exact.

Both units are defined exactly. Calculations use 50 significant digits and round only for display.

How to convert cups to ounces

Multiply US cups by 8: fl oz = cups × 8. One cup is 8 fluid ounces, 2 cups are 16 fl oz and 3/4 cup is 6 fl oz. That is exact for US cups and fluid ounces, which measure volume. Ounces on a scale measure weight: a cup of flour weighs about 4.23 oz.

Why a cup is exactly 8 fluid ounces

In US customary measure a pint is 16 fluid ounces and a cup is half a pint, so a cup is 8 fl oz with no rounding (NIST Handbook 44, Appendix C). In metric terms, a cup is 236.5882365 mL and a fluid ounce 29.5735295625 mL.

Cups to fluid ounces chart

US cupsUS fluid ounces
0.252
0.54
0.756
18
216
648

Thirds do not come out whole: 1/3 cup is 2 2/3 fl oz (2.67) and 2/3 cup is 5 1/3 fl oz (5.33). Four cups make a quart, 32 fl oz.

How much does a cup weigh in ounces?

A fluid ounce is volume and an ounce on a scale is weight, so a cup's weight depends on what fills it. By the King Arthur Baking and USDA figures in the cooking converter, one US cup weighs about:

  • Water: 8.35 oz
  • Whole milk: 8.61 oz
  • Butter: 7.97 oz, two US sticks
  • Granulated sugar: 6.98 oz
  • All-purpose flour: 4.23 oz
  • Honey: 11.85 oz

Even water is not 8 oz: a US fluid ounce of water weighs about 1.04 oz.

Which cup is your recipe using?

  • US customary cup: 236.5882365 mL, exactly 8 US fl oz. American recipes use this one.
  • US nutrition-label cup: 240 mL. The same rule, 21 CFR 101.9(b)(5)(viii), sets a fluid ounce at 30 mL, so on a label 1 cup and 8 fl oz are both 240 mL. In true US fluid ounces, 240 mL is 8.11536544844.
  • Metric cup: 250 mL, used in Australia, New Zealand and Canada. It holds 8.45350567546 US fl oz.
  • Imperial fluid ounces: older British recipes measure liquids this way. 8 imperial fl oz is 227.3045 mL, or 7.69 US fl oz.

Common mistakes

  • Weighing 8 oz of flour for one cup. That is nearly 1.9 cups, since a cup of all-purpose flour weighs about 4.23 oz.
  • Using a 250 mL metric cup for a US recipe. Each cup holds 13.41 mL, or 5.7%, more than the recipe means.
  • Thinking dry and liquid measuring cups differ in size. Both hold 8 fl oz. Level a dry cup with a straight edge, and read a liquid cup at eye level.

For the reverse, use ounces to cups. For metric volumes, use cups to mL, and for spoons, cups to tablespoons.

Worked examples

2 cup to fl oz

US cups (cup)
2 cup
US fluid ounces
16 fl oz

Checked against: Exact-fraction computation from the legal unit definitions

1 cup to fl oz

US cups (cup)
1 cup
US fluid ounces
8 fl oz

Checked against: Exact-fraction computation from the legal unit definitions

6 cup to fl oz

US cups (cup)
6 cup
US fluid ounces
48 fl oz

Checked against: Exact-fraction computation from the legal unit definitions

Questions

How many US fluid ounces are in one US cup?

1 cup is about 8 fl oz. For the US customary cup, 1 US cup = 8 US fl oz = 236.5882365 mL. These values are exact.

How do I convert US cups to US fluid ounces?

Multiply by 8: 2 cup × 8 ≈ 16 fl oz. To convert back, divide by the same factor. The factor shown may be rounded.

Is a cup 240 mL or 236.6 mL?

Both are in use. The US customary cup in recipes is approximately 236.588 mL. US nutrition labels use a rounded "legal cup" of 240 mL (21 CFR 101.9), and the metric cup used in Australia, New Zealand and Canada is 250 mL.

About this calculator

fl oz=cup×8\text{fl oz} = \text{cup} \times 8

Sources

  1. 21 CFR 101.9(b)(5)(viii), Nutrition labeling of food
  2. Safe Food for Canadians Regulations, section 241
  3. New Zealand Ministry of Education, Cooking: Measuring
  4. NSW Health, Healthy Food for Babies and Toddlers: metric cup and spoon measures
  5. NIST SP 811 (2008), Guide for the Use of the International System of Units, Appendix B
  6. NIST Handbook 44, Appendix C: General tables of units of measurement
  7. BIPM, The International System of Units (SI Brochure), 9th edition

Checked against references

This calculator includes 3 worked examples with independently sourced answers. They run in the test suite, and you can run them here too.

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