To convert fluid ounces to milliliters (fl oz to mL), multiply by 29.57353. 1 fluid ounce equals 29.57353 mL, about 5.9 times as much as a teaspoon.
| fluid ounces | milliliters |
|---|---|
| 1 fluid ounce | 29.57353 mL |
| 2 fluid ounces | 59.147059 mL |
| 5 fluid ounces | 147.86765 mL |
| 10 fluid ounces | 295.7353 mL |
| 25 fluid ounces | 739.33824 mL |
| 50 fluid ounces | 1,478.6765 mL |
| 100 fluid ounces | 2,957.353 mL |
| 250 fluid ounces | 7,393.3824 mL |
| 500 fluid ounces | 14,786.765 mL |
| 1000 fluid ounces | 29,573.53 mL |
The factor is 29.5735, which is derived rather than defined, so any decimal you see has been rounded somewhere.
For a quick estimate, multiply by 30. That is off by about 1.4%, which is fine for a rough figure and not fine for anything you are paying for or building to. Use the exact factor of 29.5735 when it matters.
The reverse factor is 0.034, so one milliliter is that many fluid ounces. Two decimal places is plenty for most purposes, and three is more than a tape measure can justify.
To anchor the scale: 1 fluid ounce is about 29.6 mL.