Ml to Fl Oz: US and UK Fluid Ounces Explained
Convert milliliters to fluid ounces using the exact US (29.5735 mL) and UK (28.4131 mL) definitions. Table, examples, and why the two ounces differ.
Milliliters to fluid ounces is one of the most error-prone conversions in daily life — not because the math is hard, but because there are *two* fluid ounces in circulation, and they don't match. Get the wrong one and a cocktail recipe, a perfume bottle spec, or a medicine dose can be off by 4%.
The formulas
US fluid ounces = milliliters ÷ 29.5735 UK (imperial) fluid ounces = milliliters ÷ 28.4131
- 1 US fl oz = 29.5735 mL exactly
- 1 UK fl oz = 28.4130625 mL exactly
The 4% gap is real. On a 500 mL bottle: 16.91 US fl oz vs 17.60 UK fl oz. Where the answer matters (labelling, medical, alcohol duty), *always* specify which fl oz you mean.
*Example:* a can of soda is 355 mL. 355 ÷ 29.5735 = 12.00 US fl oz — the reason "12 oz can" is the US standard.
Reference table (US)
| Milliliters | US fl oz | Common use |
|---|---|---|
| 5 mL | 0.169 fl oz | 1 teaspoon |
| 15 mL | 0.507 fl oz | 1 tablespoon |
| 30 mL | 1.014 fl oz | Small shot |
| 44 mL | 1.5 fl oz | US spirits pour |
| 240 mL | 8.115 fl oz | 1 US cup |
| 355 mL | 12.00 fl oz | Standard soda can |
| 500 mL | 16.91 fl oz | Half-litre bottle |
| 750 mL | 25.36 fl oz | Wine bottle |
| 1,000 mL | 33.81 fl oz | 1 litre |
For any custom value, the Ml to Fl Oz converter does it in full precision.
Why the US and UK fluid ounces differ
The two fluid ounces come from different pre-metric definitions of the *gallon*.
- The US gallon was inherited from the English wine gallon of 1707 — 231 cubic inches ≈ 3.785 L. Split into 128 fluid ounces, that gives 29.5735 mL each.
- The imperial gallon was defined by the UK Weights and Measures Act 1824 as the volume of 10 pounds of pure water at 62 °F — about 4.546 L. Split into 160 imperial fluid ounces, that gives 28.4131 mL each.
So the US kept the older, smaller gallon and split it into 128 oz; the UK adopted a bigger gallon and split it into 160 oz — with the surprising result that the imperial fluid ounce is slightly *smaller* than the US one, even though the imperial gallon is *bigger*. All modern definitions are metric-traceable and maintained by NIST and the UK's National Physical Laboratory.
Cooking, medicine, and cosmetics
- Cooking. US recipes use fluid ounces and cups; UK recipes are almost entirely metric today. A "cup" in a US recipe is 240 mL — meaningfully different from the 250 mL "metric cup" used in Australia.
- Medicine. In the US, over-the-counter liquid medicine still lists dose in tsp/tbsp/fl oz alongside mL. The FDA now recommends mL as the primary unit to reduce dosing errors.
- Cosmetics and perfume. Almost always dual-labelled: "50 mL / 1.7 fl oz". The 1.7 is US fl oz; you'd get 1.76 with the UK definition.
FAQ
Which fluid ounce should I use? Default to US fluid ounces unless the recipe, label, or spec explicitly says "imperial". Almost every consumer product in the US and much of the world's cocktail literature is US fl oz.
How many mL is 1 fl oz? US: 29.5735 mL. UK: 28.4131 mL. The Ml to Fl Oz converter supports both.
Is a "shot" the same everywhere? No. A US "standard shot" is 44 mL (1.5 fl oz); a UK "single" is typically 25 mL or 35 mL; European bar measures vary further. Cocktail recipes almost always assume the US 1.5 fl oz shot.
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*For a fast, precise conversion in either system, the free Ml to Fl Oz Converter has both US and imperial modes.*