One US cup contains exactly 8 US fluid ounces. This is the standard defined by the US customary measurement system and is the figure you will see on virtually every American measuring cup. According to the US National Institute of Standards and Technology (NIST), 1 US cup is legally defined as 8 US fluid ounces, which equals 236.588 milliliters (https://www.nist.gov/pml/weights-and-measures). That single fact covers the vast majority of everyday cooking and baking needs. When a recipe written for a US audience calls for 1 cup of milk, water, broth, or juice, you can pour exactly 8 fl oz and be perfectly accurate. The relationship scales linearly: 2 cups equal 16 fl oz, 3 cups equal 24 fl oz, and so on.
The table below covers the most frequently used cup fractions and their fluid-ounce equivalents, all based on the 1 cup = 8 fl oz standard.
Cup Measurement | Fluid Ounces (fl oz) | Milliliters (mL)
1/8 cup | 1 fl oz | 29.57 mL
1/4 cup | 2 fl oz | 59.15 mL
1/3 cup | 2.67 fl oz | 78.86 mL
1/2 cup | 4 fl oz | 118.29 mL
2/3 cup | 5.33 fl oz | 157.73 mL
3/4 cup | 6 fl oz | 177.44 mL
1 cup | 8 fl oz | 236.59 mL
1.5 cups | 12 fl oz | 354.88 mL
2 cups | 16 fl oz | 473.18 mL
4 cups (1 quart) | 32 fl oz | 946.35 mL
Keep this table bookmarked any time you are scaling a recipe up or down. The 1/3 cup and 2/3 cup values are rounded to two decimal places because the underlying fractions are repeating decimals.
A common source of confusion is the difference between a fluid ounce and a dry ounce. A fluid ounce is a unit of volume — it tells you how much space a liquid occupies. A dry ounce is a unit of weight. They share a name and similar numbers for water at room temperature, but they are fundamentally different measurements.
For water, 8 fluid ounces happens to weigh almost exactly 8.345 dry ounces (about 236.6 grams), which is close enough that many people treat them as equal. However, 1 cup of all-purpose flour weighs roughly 4.25 oz (about 120 grams) by weight, not 8 oz, because flour is much less dense than water. One cup of honey, conversely, weighs around 12 oz because honey is denser than water.
The practical takeaway: use fluid ounces when measuring liquids by volume with a measuring cup, and use a kitchen scale when a recipe specifies dry ounces or grams for ingredients like flour, sugar, or nuts. Professional bakers and pastry chefs almost universally use weight measurements for dry ingredients because volume measurements are sensitive to how tightly an ingredient is packed.
Not every cup is the same size, and this matters when following recipes from cookbooks published outside the United States.
1. US customary cup: 8 US fluid ounces = 236.59 mL
2. US legal cup (used in nutrition labeling): 8.12 US fluid ounces = 240 mL
3. UK imperial cup (now largely obsolete): 10 imperial fluid ounces = 284.13 mL
4. Metric cup (used in Australia, Canada, and New Zealand): 8.45 US fluid ounces = 250 mL
5. Japanese cup: 6.76 US fluid ounces = 200 mL
The difference between a US cup and a metric cup is about 13.4 mL, which is small enough to ignore for most casual recipes but can compound in baked goods when several cups of an ingredient are used. If you are converting an Australian recipe, for example, substituting 250 mL per cup rather than 236.59 mL will produce more accurate results. When in doubt, check the recipe's country of origin and adjust accordingly.
Knowing the conversion is only half the job — measurement technique affects accuracy just as much.
1. Use the right tool: Liquid measuring cups are designed with a spout and a fill line you read at eye level. Dry measuring cups are meant to be overfilled and leveled off with a straight edge.
2. Level dry ingredients: Scoop flour or sugar into a dry measuring cup, then sweep a flat spatula or knife across the top. Do not pack unless the recipe specifically says to (brown sugar is a common exception).
3. Read liquid at eye level: Set the measuring cup on a flat surface and crouch to read the meniscus at eye level rather than reading from above, which introduces parallax error.
4. Use a kitchen scale for precision: According to the King Arthur Baking Company's measurement guides, weighing ingredients rather than measuring by volume can improve baking consistency significantly, especially for flour. (https://www.kingarthurbaking.com/learn/guides/baking-with-the-right-flour)
5. Temperature matters for liquids: Some recipes, particularly candy making, specify volume at a set temperature because liquid density changes with heat.
6. Double-check unit labels on recipe apps and websites: Some platforms default to metric measurements depending on the user's region settings, which can silently change what "1 cup" means in context.
Scaling a recipe is straightforward once you know that 1 cup equals 8 fl oz. Multiply or divide both the cup measurement and the fluid-ounce equivalent by the same factor.
If a recipe calls for 3.5 cups of chicken broth and you want to halve the recipe, you need 1.75 cups, which equals 14 fl oz. If you only have a liquid measuring cup marked in ounces, pour to the 14 fl oz line.
For larger batch cooking, it helps to think in quarts and gallons: 4 cups equal 1 quart (32 fl oz), and 16 cups equal 1 gallon (128 fl oz). These anchor points prevent arithmetic errors when scaling by large factors.
When scaling baked goods, be aware that leavening agents like baking powder and baking soda do not always scale linearly. Standard culinary guidance suggests reducing the leavening by about 25 percent when more than doubling a recipe, to avoid an overly risen or bitter result. Volume and fluid-ounce conversions scale perfectly, but overall recipe chemistry may require minor adjustments beyond simple multiplication.
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In the US customary system, 1 cup equals 8 fluid ounces by volume. However, the US legal cup used in nutrition labeling is 240 mL, which is approximately 8.12 fl oz. Outside the US, metric cups (250 mL) and UK cups (284 mL) differ from the US standard, so the answer depends on which measurement system the recipe or label uses.
Because fluid ounces measure volume, not weight. Eight fluid ounces is a volume equal to 236.59 mL. Flour is much less dense than water, so 1 cup of flour occupies 8 fl oz of space but weighs only about 4.25 oz (roughly 120 grams). Ingredients denser than water, like honey or molasses, will weigh more than 8 oz per cup.
One half cup equals 4 US fluid ounces, or approximately 118.29 milliliters. This is one of the most commonly used fractions in cooking and baking, and most standard liquid measuring cups include a 4 fl oz or 1/2 cup line.
Multiply the number of cups by 8 to get fluid ounces. For fractions, remember the anchors: 1/4 cup = 2 fl oz, 1/2 cup = 4 fl oz, and 3/4 cup = 6 fl oz. For amounts like 1/3 cup, the equivalent is approximately 2.67 fl oz, which you can approximate as just under 3 fl oz for most non-baking purposes.
No, not for volume measurements. One cup of water, one cup of milk, and one cup of vinegar all occupy the same volume: 8 fluid ounces. However, they will have different weights in dry ounces or grams because their densities differ. Volume-based cup-to-fluid-ounce conversions are constant regardless of what liquid is being measured.