What this calculator does
Change milliliters (mL) into US fluid ounces (fl oz), or fluid ounces into milliliters. A milliliter is one thousandth of a liter. It's the metric unit printed on nearly every drink, cosmetic and cleaning product sold around the world. The US fluid ounce is the unit Americans see on the same products, from a can of soda to a bottle of shampoo. Many labels show both numbers. When only one is printed, this conversion fills in the other.
A US fluid ounce is officially 1/128 of a US gallon, and the gallon is exactly 231 cubic inches. Since the inch has an exact metric length, that works out to 1 US fl oz = 29.5735295625 mL. The decimal stops there, so the value is exact. This page uses it both ways. It also labels which ounce it means, because the British imperial fluid ounce is a different size.
Where it's used
Why this math matters outside the classroom:
- Travel liquids. The 100 mL carry-on liquid limit is about 3.4 fl oz.
- Soda cans. Shoppers comparing drinks see that a 355 mL can is the same as a 12 fl oz can.
- Wine bottles. A standard 750 mL wine bottle holds about 25.4 fl oz.
- Baby bottles. A 240 mL baby bottle holds about 8.1 fl oz.
- Cosmetics. A 50 mL bottle of lotion is about 1.7 fl oz.
Grade level and standards: Grades 5–6; Common Core State Standards for Mathematics 6.RP.A.3.d. © Copyright 2010. National Governors Association Center for Best Practices and Council of Chief State School Officers. All rights reserved.
How to use it
- Type the amount, either in milliliters or in US fluid ounces.
- Pick the direction: milliliters to fluid ounces, or fluid ounces to milliliters.
- Read the result and the steps. Then use the table to look up common container sizes.
What the inputs mean
- Value to convert
- An amount of liquid. For mL → fl oz, enter milliliters. For fl oz → mL, enter US fluid ounces.
- Direction
- Tells the calculator which unit you typed in. The table below flips to match.
Formula and method
mL = US fl oz × 29.5735295625 US fl oz = mL ÷ 29.5735295625 ≈ mL × 0.0338140227
In the formulas, mL is milliliters and US fl oz is US fluid ounces. The official definition gives the exact number of milliliters in one ounce. So changing ounces to milliliters is a plain multiplication, with no rounding at all.
Going from milliliters to ounces divides by the same number. Its flip side, 1 ÷ 29.5735295625 (about 0.033814), has digits that never end. So the calculator divides, instead of multiplying by a rounded number.
Worked example
A water bottle is labeled 500 mL. How many US fluid ounces is that?
- 1 US fl oz is exactly 29.5735295625 mL, so divide by that: 500 ÷ 29.5735295625.
- 500 ÷ 29.5735295625 = 16.9070113509…
Result: 500 mL is about 16.9 US fl oz. That's why half-liter bottles in the US are often labeled 16.9 fl oz.
Understanding the result
Quick estimate: treat one fluid ounce as 30 mL. Multiplying ounces by 30 gives about 1.4% too many milliliters. So 8 fl oz becomes 240 mL instead of 236.6 mL. To go the other way, divide milliliters by 30 and add a little.
Familiar sizes: a 12 fl oz can is 354.9 mL, usually printed as 355 mL. A 750 mL wine bottle holds about 25.4 fl oz. A liter is about 33.8 fl oz. And the 100 mL limit for carry-on liquids at many airports is roughly 3.4 fl oz.
Watch out: an ounce on a jar of peanut butter or a bag of chips is a weight, not a volume. Only ounces marked "fl oz" can be changed to milliliters this way. Weight ounces need the weight converter, or the density of the food (how heavy it is for its size).
Assumptions and limitations
- Ounces are US fluid ounces, each 1/128 of a 231-cubic-inch gallon.
- Milliliters are exactly 1 cubic centimeter each.
- The UK imperial fluid ounce (28.4130625 mL) is about 4% smaller and isn't used here. You can pick it in the general volume converter.
- It doesn't turn weight ounces into milliliters. That would need the density of the substance.
Frequently asked questions
How many mL are in one fluid ounce?
Exactly 29.5735295625 mL for the US fluid ounce. Rounded, that's 29.57 mL, or roughly 30 mL for kitchen use.
Is a UK fluid ounce the same?
No. The imperial fluid ounce is 28.4130625 mL, about 96% of the US one. Older British recipes and some UK labels use it. So 10 imperial fl oz is about 284 mL, while 10 US fl oz is about 296 mL.
How many fluid ounces is 1 liter?
About 33.814 US fl oz. A liter is a little more than a US quart, which is 32 fl oz.
Can I use 30 mL as an ounce for medicine?
Please don't use kitchen conversions for medicine at all. Measure doses with the dosing cup or syringe that comes with the product. It's marked in the units the label uses.
How this calculator is checked
Method: US customary definition: 1 US gal = 231 in³ = 3.785411784 L; 1 US fl oz = 1/128 gal = 29.5735295625 mL exactly. The calculation is covered by automated tests with known reference values and edge cases. Last updated 2026-10-18. Found a problem? Tell us.
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