The exact equivalent
A US fluid ounce is 29.5735 millilitres, so a millilitre is 0.0338140 fluid ounces. The imperial fluid ounce is 28.4131 ml, slightly smaller.
1 ml = 0.03381402 fl oz
1 fl oz = 29.57352956 ml
How to convert it by hand
Just multiply by the conversion factor. To go from millilitres to US fluid ounces, multiply by 0.033814; to come back, divide by that same number or multiply by 29.57353.
For example: 25 ml × 0.033814 = 0.8454 fl oz.
A tip that saves mistakes: check the result goes the way you expect. If US fluid ounces are a smaller unit than millilitres, the number has to come out bigger. If it comes out smaller, you divided when you should have multiplied.
Conversion table
| ml | fl oz |
|---|---|
| 1 | 0.0338 |
| 2 | 0.0676 |
| 5 | 0.1691 |
| 10 | 0.3381 |
| 20 | 0.6763 |
| 50 | 1.6907 |
| 100 | 3.3814 |
Reference points to picture it
| Reference | Equals |
|---|---|
| A can of drink | 330 ml = 11.2 fl oz |
| A cabin baggage liquid limit | 100 ml = 3.4 fl oz |
| A standard water bottle | 500 ml = 16.9 fl oz |
| A US cup | 237 ml = 8 fl oz |
The trick for doing it in your head
Divide by 30. For 500 ml: 500 ÷ 30 = 16.7 fluid ounces, against a true 16.9.
It is fine for getting by without a phone, but not for anything that depends on precision: in a recipe, on a building site or in a dose, use the exact conversion.