US fluid ounces and milliliters
The US fluid ounce is 1/128 of a US gallon: exactly 29.5735295625 milliliters. Drink cans and bottles, cosmetics and US recipes use fluid ounces. It measures volume, unlike the ounce of weight.
The milliliter is one thousandth of a liter, the same volume as one cubic centimeter. Medicine doses, cosmetics, small bottles and metric recipes are measured in milliliters.
Worked example
Convert 16 fl oz: 16 × 29.5735295625 = 473.176473, so 16 US fluid ounces is 473.176473 milliliters. Likewise 20 fl oz = 591.4705913 mL.
Estimating in your head
Multiply by 30 for a quick figure; it is off by about 1.4%. For 16 fl oz that gives 480 mL, against 473.176 exactly.
Going the other way
To convert milliliters to US fluid ounces, divide by 29.5735295625 (or multiply by 0.0338140227018). The swap button between the boxes opens that page.
How this works
mL = fl oz × 29.5735295625
1 fl oz = 0.0000295735295625 m³ and 1 mL = 0.000001 m³, both by definition, so the factor is their ratio: 29.5735295625 exactly. Results drop binary floating-point noise beyond 15 significant digits and display at the precision you choose (6 significant figures by default). Copy result copies the full value.
Frequently asked
How many milliliters are in a US fluid ounce?
1 US fluid ounce = 29.5735295625 milliliters, exactly. The value follows from the unit definitions, so it never changes.
How do I convert US fluid ounces to milliliters?
Multiply by 29.5735295625. For example, 20 fl oz × 29.5735295625 = 591.4705913 mL.
What is 100 fl oz in milliliters?
100 fl oz = 2,957.352956 mL. The table next to the converter lists more common values.
Is the result rounded?
Only on screen. The page computes with the exact definitions and removes floating-point noise past 15 significant digits; pick 3 to 12 significant figures, or use Copy result for the full value.
Sources
- NIST SP 811 Appendix B.8 — Factors for units listed alphabetically
- NIST Handbook 44 — Appendix C, General tables of units of measurement
- Wikipedia — United States customary units
Reviewed Oct 17, 2026 · test vectors fixtures/units/volume/oz-to-ml/