Example 1
- 1
8 fl oz
1 × 8 = 8
Cups to Ounces Calculator
Enter a US cup count. The calculator multiplies it by 8. One cup is 8 fl oz, two cups are 16 fl oz, half a cup is 4 fl oz. This is not a mass ounce and not a 250 ml glass.
Result
Enter a US cup count. The result will appear here.
If you start from fluid ounces, open ounces to cups. For a 250 ml glass, use cup to mass.
How results are calculated
cups2
fl oz16
The cups to ounces calculator converts US cups to fluid ounces. The formula is fl oz = cups × 8. One US cup is exactly 8 fl oz, two cups are 16 fl oz, and half a cup is 4 fl oz.
The other way, fluid ounces are divided by 8. Eight fl oz is 1 US cup. That is the US-cup definition, not an approximation.
Enter a volume and keep cups to ounces if you start from cups. A comma works like a period. Zero stays zero. A negative number is rejected.
This is not a mass ounce and not a 250 ml glass. Mass ounces are on the grams and ounces page. A 250 ml glass is on cup to mass.
The neighbouring ounces to cups page uses the same constant 8, but defaults to starting from fl oz.
Enter 1 with the cups-to-ounces direction and compare the result with 8 fl oz. At 2 cups the result is 16 fl oz. At 0.5 cup the result is 4 fl oz.
How to use this calculator
- Keep the direction US cups to fluid ounces.
- Enter 1. The result is 8 fl oz.
- Enter 2. The result is 16 fl oz.
- Enter 0.5. The result is 4 fl oz.
- To start from ounces, open ounces to cups.
Formula
fl oz = cups × 8 · cups = fl oz / 8
A US cup is 8 fl oz by definition. Volume must be zero or greater.
US cup and fl oz
1 US cup = 8 fl oz. 2 cups = 16 fl oz.
- US cup
- 8 fl oz by definition. This is not a 250 ml glass.
- fl oz
- US fluid ounce, not a mass ounce.
- 8
- US-cup definition constant.
Examples
Example 2
- 2
16 fl oz
2 × 8 = 16
Example 3
- 0.5
4 fl oz
0.5 × 8 = 4
Related calculators
Frequently asked questions
How are US cups converted to fluid ounces?
The calculator multiplies the US cup count by 8. One cup is 8 fl oz. Two cups are 16 fl oz. The other way, fluid ounces are divided by 8.
Is this a mass ounce?
No. Only the fluid ounce is converted here. Mass ounces are on the grams and ounces page.
Is a US cup a 250 ml glass?
No. A US cup is 8 fl oz. A 250 ml glass is on the cup to mass page.
Are zero or negative volumes allowed?
Zero is allowed and stays zero. A negative volume is rejected.
Does a comma in 0.5 work?
Yes. A comma and a period are the same fraction. Half a cup is 4 fl oz.
Where do I start from ounces instead of cups?
On ounces to cups. There the default direction starts from fl oz.
Where do I convert millilitres without a cup?
On fluid ounces to ml or ml to fl oz. Those pages have no US-cup field.
What do the fields in the result panel show?
The primary result is the converted volume. Beside it you see the other side, the direction, and the × 8 or ÷ 8 constant.
Is 1.5 cups 12 fl oz?
Yes. One and a half times 8 is 12 fl oz.
How is this different from a 15 ml tablespoon?
Here you count a US cup and fl oz. A 15 ml tablespoon and a 5 ml teaspoon are on the spoon page.
Knowledge sources
A US cup is defined as 8 fluid ounces.
Page updated October 12, 2026.