How Many Ounces Are in a Cup?
By ToolNimba Editorial Team June 20, 2026 3 min read
Quick answer
There are 8 fluid ounces in 1 US cup. So 2 cups is 16 fl oz, and half a cup is 4 fl oz.
That 8 ounce figure is for liquids measured by volume, which is exactly what a measuring cup does. It holds true for water, milk, juice, oil, broth and any other liquid, because you are measuring the space the liquid fills rather than its weight. A cup of honey and a cup of water both equal 8 fluid ounces of volume even though the honey is far heavier on a scale.
Where the 8 ounce number comes from
The US customary cup is defined as exactly 8 US fluid ounces, which works out to about 236.6 milliliters. The cup sits inside a tidy system of volume units: 1 cup is 8 fluid ounces, 2 cups make a pint, 2 pints make a quart, and 4 quarts make a gallon. Because each step doubles or scales cleanly, you can chain them together. One gallon is 128 fluid ounces, which is simply 16 cups stacked end to end.
A fluid ounce is a measure of volume, not weight, which is the single most important idea on this page. The word "ounce" doing double duty for both volume (fluid ounces) and weight (dry ounces on a scale) is the reason so many cooks get confused, so keep the two firmly separated in your head.
Cup to fluid ounce chart
| Cups | Fluid ounces | Tablespoons | Milliliters |
|---|---|---|---|
| 1/8 cup | 1 fl oz | 2 tbsp | 30 ml |
| 1/4 cup | 2 fl oz | 4 tbsp | 59 ml |
| 1/3 cup | 2.7 fl oz | 5.3 tbsp | 79 ml |
| 1/2 cup | 4 fl oz | 8 tbsp | 118 ml |
| 3/4 cup | 6 fl oz | 12 tbsp | 177 ml |
| 1 cup | 8 fl oz | 16 tbsp | 237 ml |
| 2 cups | 16 fl oz | 32 tbsp | 473 ml |
| 4 cups | 32 fl oz | 64 tbsp | 946 ml |
If you ever need to go the other direction, just divide the fluid ounces by 8. So 12 fl oz is 1.5 cups, and 20 fl oz is 2.5 cups. The same logic scales up to bigger jobs, which is handy when a recipe lists ounces in a gallon or a drink is sold by the quart.
Why dry ingredients are different
Dry ingredients are trickier. A dry ounce is a unit of weight, not volume, so the number of ounces in a cup depends entirely on what you are scooping. A cup of feathers and a cup of lead would never weigh the same, and the same principle applies to flour versus sugar. This is why a recipe can call for a cup of two different ingredients and produce two very different weights on the scale.
| Ingredient (1 cup) | Approx. weight (oz) | Approx. weight (g) |
|---|---|---|
| All-purpose flour | 4.25 oz | 120 g |
| Granulated sugar | 7 oz | 200 g |
| Brown sugar (packed) | 7.5 oz | 213 g |
| Butter | 8 oz | 227 g |
| Water | 8.3 oz | 236 g |
| Rolled oats | 3.2 oz | 90 g |
For dry baking, weighing in grams is the most accurate approach by a wide margin. A loosely scooped cup of flour can weigh 20 percent less than a packed one, and that gap is enough to turn a tender cake dense. If you want to learn the gram side of the story, see our guide on grams in a cup.
US vs UK and metric
This guide uses US customary cups. A UK or metric cup is 250 ml (about 8.45 fl oz), and an imperial fluid ounce is slightly smaller than a US one, so a US gallon and an imperial gallon are not the same size either. Always match your recipe to your measuring set.
Practical kitchen examples
Conversions feel abstract until you put them to work. Here are everyday situations where knowing 8 fl oz per cup saves the day:
- A soup recipe calls for 4 cups of broth but your carton lists 32 fl oz. They match exactly, so use the whole carton.
- You want to double a cocktail that uses 6 fl oz of juice. That is 3/4 cup, so doubled it becomes 1.5 cups or 12 fl oz.
- A coffee mug holds about 12 fl oz, which is 1.5 cups, so a recipe asking for 1 cup of coffee fills two thirds of your mug.
- A standard US water bottle is often 16.9 fl oz, just over 2 cups, handy for rough hydration math.
- Baby formula and medicine often list both cups and fluid ounces, and they line up at the same 8 to 1 ratio.
Common mistakes to avoid
Most measuring errors come from a handful of repeat offenders. Watch for these:
- Confusing fluid ounces with weight ounces. A cup of flour is 8 fluid ounces of volume but only about 4.25 ounces on a scale.
- Using a UK recipe with US cups. The 250 ml metric cup is roughly 5 percent larger than the US cup, which adds up in baking.
- Measuring liquids in a dry cup. Topping a dry cup to the brim with liquid almost always overshoots the line.
- Eyeballing 1/3 cup as half of a half cup. One third is 2.7 fl oz, not the 2 fl oz you would get from quartering.
- Packing flour by scooping straight from the bag, which compresses it and overloads the cup.
Convert any amount instantly
For other kitchen conversions like cups to grams, tablespoons to teaspoons, or fluid ounces to milliliters, the cooking converter below does the math for you in a single tap. It handles both volume and ingredient weight, so you never have to guess whether your ounce is a fluid ounce or a dry one.
🥄 Try the free tool Cooking Measurement Converter Free cooking measurement converter. Switch between cups, tablespoons, teaspoons, fluid ounces, pints, quarts, ml and litres instantly. US customary units.Frequently asked questions
How many ounces are in a cup?
There are 8 fluid ounces in 1 US cup. This applies to any liquid measured by volume, including water, milk, oil and juice, because you are measuring the space it fills. For dry ingredients measured by weight on a scale, the ounces per cup vary by ingredient.
How many ounces in half a cup?
There are 4 fluid ounces in half a US cup, and 2 fluid ounces in a quarter cup. The pattern is simple: each cup is 8 fluid ounces, so you halve or quarter that figure as needed. Three quarters of a cup works out to 6 fluid ounces.
Is a dry cup the same as a liquid cup?
They hold the same volume, 8 fluid ounces. The difference is the tool. Liquid measuring cups are clear with a spout and lines for pouring, while dry measuring cups are filled and leveled flat with a straight edge. For dry baking, weighing is far more accurate than measuring by volume.
Why does a cup of flour weigh less than 8 ounces?
Because flour is light and full of air. A cup of flour fills 8 fluid ounces of volume but weighs only about 4.25 ounces on a scale. Fluid ounces measure space, while weight ounces measure mass, so a light, fluffy ingredient weighs far less than the same volume of a dense one.
Is a UK cup the same as a US cup?
No. A US customary cup is 8 fluid ounces, about 237 ml, while a UK or metric cup is 250 ml, roughly 5 percent larger. The imperial fluid ounce is also slightly smaller than the US one. For reliable results, match your recipe to a measuring set from the same region.
How do I convert ounces back to cups?
Divide the number of fluid ounces by 8. So 16 fl oz is 2 cups, 12 fl oz is 1.5 cups, and 4 fl oz is half a cup. This only works for fluid ounces, which measure volume. If your figure is a weight in ounces, you need the ingredient density to convert it.