How many fl oz is a cup of water?

A cup is a common unit of measurement used for liquids and powders in cooking. But how much liquid is actually in a standard cup measure? When looking at fluid ounces (fl oz), just how many fl oz are in a cup? Let’s take a closer look.

Quick Answer

A standard cup measure holds 8 fluid ounces of liquid. So if you’re measuring water, juice, milk, or any other liquid, a full cup measure will be 8 fl oz.

Measuring Cup Sizes

There are a few different sizes of measuring cups to be aware of:

  • Standard (US Customary) cup: 8 fl oz
  • Legal (US Customary) cup: 8.12 fl oz
  • Metric cup: 250 ml
  • Imperial (UK) cup: 10 fl oz

The most common type of measuring cup used in US home kitchens is the standard US cup at 8 fl oz. Measuring cups in the US are usually labeled with fluid ounces and cups.

Standard US Cup

The standard US customary cup, used for both liquid and dry ingredients, contains 8 fluid ounces. It’s the standard cup size used in most American recipes.

One US cup is equal to:

  • 8 fluid ounces (fl oz)
  • 236.6 milliliters (ml)
  • Half a US pint
  • One 16th of a US gallon

So if you fill an 8 fl oz measuring cup to the brim with water, you have the equivalent of 1 cup of water.

Legal US Cup

There is also a “legal” US cup used by the United States FDA for nutrition labeling. The legal cup is slightly larger at 8.12 fl oz. This is to account for the fact that when measuring by hand, people often don’t fill cups perfectly to the top.

The 8.12 fl oz legal US cup is equal to:

  • 8.12 fluid ounces (fl oz)
  • 240 milliliters (ml)
  • One 16th of a US gallon

Unless a recipe specifies the legal cup size, it’s safe to assume it means the standard 8 fl oz cup.

Metric Cup

In metric measurements, a cup is 250 milliliters. This is slightly larger than both the standard US and legal US cup sizes.

One metric cup is equal to:

  • 250 milliliters (ml)
  • 8.45 fluid ounces

Imperial Cup

In the Imperial (UK) system, one cup is equal to 10 Imperial fluid ounces. The Imperial cup is larger than the US cup.

One Imperial cup equals:

  • 10 Imperial fluid ounces (fl oz)
  • 284 milliliters (ml)
  • One 20th of an Imperial gallon

Make sure you know which cup measurement a recipe is using before substituting cup amounts.

Converting Between Cups and Fluid Ounces

Since cups and fluid ounces are common liquid measurements, it’s useful to know conversions between them:

Cups Fluid Ounces
1 cup 8 fl oz (US)
2 cups 16 fl oz
1/2 cup 4 fl oz
1/4 cup 2 fl oz

To convert fluid ounces to cups:

  • Divide fluid ounces by 8 to get US cups
  • Divide fluid ounces by 10 to get Imperial cups

So 14 fl oz would be equal to:

  • 14 fl oz / 8 fl oz per cup = 1 3/4 US cups
  • 14 fl oz / 10 fl oz per cup = 1 2/5 Imperial cups

Metric Conversions

Here are some handy conversions between milliliters, fluid ounces, and metric cups:

Milliliters Fluid Ounces Metric Cups
250 ml 8.45 fl oz 1 cup
125 ml 4.2 fl oz 1/2 cup
59 ml 2 fl oz 1/4 cup

Using Cups to Measure Liquids

Measuring cups are marked with fractional cup measurements. Common increments are:

  • 1/4 cup
  • 1/3 cup
  • 1/2 cup
  • 2/3 cup
  • 3/4 cup
  • 1 cup
  • 1 1/2 cups
  • 2 cups

Measuring cups for liquids have pouring spouts and handles to easily pour out liquids without spilling. To accurately measure liquids using a cup measure:

  1. Place the liquid measuring cup on a flat surface.
  2. View the measurement markings at eye level.
  3. Fill the cup to the desired measurement marking.
  4. Bend down to check the meniscus (curve of the liquid surface) is perfectly level with the marking.

For thick liquids like oil or syrup, you may need to view the meniscus from below to get an accurate reading.

Tips for Measuring Liquids

  • Use clear measuring cups so you can see the markings.
  • Add liquid gradually when nearing the desired amount.
  • Set the cup on the counter rather than holding it when filling for better accuracy.
  • Use a spatula or finger to remove extra liquid above the desired marking.
  • To measure sticky liquids like honey, oil the cup first so it pours out easily.

Using Cups to Measure Dry Ingredients

While dry measuring cups can be used to measure liquids, liquid measuring cups should not be used to measure dry ingredients. Dry measuring cups are better suited for measuring powders, grains, and granulated ingredients.

Dry measuring cups come in nested sets so they don’t take up much space. They are typically made of sturdy metal or plastic.

To measure dry ingredients:

  1. Use a spoon or scoop to add the ingredient to the measuring cup.
  2. Heap it above the rim and level it off using a straight edge like the back of a knife.
  3. Don’t tap or pack down the ingredient into the cup unless a recipe specifies.

Tips for Measuring Dry Ingredients

  • Brown sugar needs to be packed down into the cup measure.
  • Never measure over your mixing bowl, always over a separate plate or sheet of wax paper.
  • To measure sticky ingredients like brown sugar, coat the cup with nonstick spray first.
  • When measuring multiple dry ingredients, measure them one at a time to avoid mixing.

How Many Cups in a Gallon?

Since gallons are a common size for purchasing liquids like milk, juice, and water, it can be useful to know how many cups are in a gallon. The number of cups in a gallon depends on the cup size:

  • US gallon: There are 16 standard 8 oz cups in a US gallon, for a total of 128 fl oz.
  • Imperial gallon: There are 20 Imperial 10 oz cups in an Imperial gallon, also totaling 128 fl oz.
  • Metric: There are about 3.8 liters in a gallon. Since a metric cup is 250 ml, there are 15.2 metric cups in a gallon.

Cups to Gallons Conversion

To convert cups to gallons:

  • Multiply US cups by 0.0625 (1/16) to get US gallons
  • Multiply Imperial cups by 0.05 (1/20) to get Imperial gallons
  • Multiply metric cups by 0.0656 to get US gallons

So for example:

  • 4 US cups x 0.0625 = 0.25 gallons
  • 5 Imperial cups x 0.05 = 0.25 Imperial gallons
  • 6 metric cups x 0.0656 = 0.39 gallons

Common Liquid Measurements

Here’s a quick overview of some of the most common liquid measurements to be familiar with when cooking and baking:

Fluid Ounces

  • Abbreviated as fl oz
  • Main imperial and US customary unit for volumes of liquid
  • 1 US fluid ounce = 29.57 ml
  • 16 fl oz = 1 US pint


  • The most common metric unit for liquid volume
  • 1 liter = 1000 ml
  • 1 ml = about 0.03 fl oz


  • Used for measuring liquid and dry ingredient volumes
  • 1 US cup = 8 fl oz = 16 tablespoons = 48 teaspoons
  • 1 Imperial cup = 10 fl oz
  • Common in cooking recipes and kitchen measuring


  • 2 US cups = 1 US pint = 16 fl oz
  • 2 Imperial cups = 1 Imperial pint = 20 fl oz
  • A common size for milk, juice, cream, and other liquids


  • 4 US cups = 2 US pints = 32 fl oz = 1 US quart
  • 40 Imperial fl oz = 1 Imperial quart
  • Often used for buying juices, stocks, buttermilk, and other ingredients


  • 16 US cups = 8 US pints = 4 US quarts = 1 US gallon
  • 20 Imperial cups = 4 Imperial quarts = 1 Imperial gallon
  • Used for purchasing milk, water, cider, and other liquids

Knowing these conversions allows you to substitute one liquid measurement for another in recipes.

Measuring Cup FAQs

Here are answers to some frequently asked questions about measuring cups and liquid volumes:

How many tablespoons are in a cup?

There are 16 tablespoons (tbsp) in 1 US cup. Since 1 tbsp = 3 teaspoons (tsp), there are also 48 tsp in a cup.

Can I use any cup for measuring liquids?

No, to accurately measure liquids you should use a clear liquid measuring cup with pour spout and handle markings. Normal drinking glasses and mugs are not reliable for measuring precise volumes.

What can I use instead of a measuring cup?

For a small amount, you can substitute a spoon or tablespoon. 1 tablespoon = 1/2 fluid ounce. If you don’t have measuring cups, a kitchen scale can help measure liquids by weight.

How do I measure oil without a liquid cup?

If you don’t have a liquid measuring cup, pour the oil into a dry measuring cup or spoon to the needed level. A scale can also help measure oil amounts.

Should I use the same cup for dry and wet ingredients?

No, use a liquid cup for wet ingredients and dry cup for dry. Dry cups give a more accurate measure for dry goods. Be sure to label cups to avoid mixing up wet and dry ingredients.


Knowing how many fluid ounces are in a cup, and being familiar with converting between cups, fl oz, liters, and gallons allows you to easily substitute liquid amounts in any recipe. Keep in mind the differences between the standard US cup (8 fl oz), legal US cup (8.12 fl oz), metric cup (250 ml), and Imperial cup (10 fl oz) to get accurate measurements every time.

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