Convert Fluid Ounces to Milliliters
Convert US fluid ounces into milliliters for cocktails, baby bottles, perfume sizes and travel rules abroad.
1 fl oz = 29.5735 ml
One US fluid ounce equals exactly 29.5735295625 millilitres. To convert US fluid ounces to millilitres, multiply by 29.5735 — so 8 fl oz = 236.59 ml and 12 fl oz = 354.88 ml. The UK imperial fluid ounce is a different unit at 28.4131 ml, and confusing the two introduces roughly a 4 percent error in either direction. For quick work, treating a fluid ounce as 30 ml is close enough for cooking and wrong for medicine, where dosing should use the exact figure. Familiar anchors: a US soda can is 12 fl oz or 355 ml, a standard wine pour is 5 fl oz or 148 ml, and a US cup is 8 fl oz or 237 ml. The distinction that causes real errors is weight versus volume — a fluid ounce measures space and an ounce measures mass, and they coincide only for water, so recipes must specify which is meant.
Quick reference: fluid ounces (us) to milliliters
| Fluid ounces (US) | Milliliters |
|---|---|
| 1 | 29.57 ml |
| 2 | 59.15 ml |
| 3.4 | 100.55 ml (TSA limit) |
| 4 | 118.29 ml |
| 8 | 236.59 ml (1 US cup) |
| 12 | 354.88 ml |
| 16 | 473.18 ml (1 US pint) |
| 16.9 | 499.79 ml |
| 32 | 946.35 ml (1 US quart) |
How do you convert fluid ounces (us) to milliliters?
Formula: millilitres = US fluid ounces × 29.5735 • An 8 fl oz cup of coffee → 8 × 29.5735 = 236.59 ml, which is where the 236.588 ml US cup comes from. • A 12 fl oz soda can → 12 × 29.5735 = 354.88 ml, against the 330 ml can standard in Europe. • A 3.4 fl oz travel bottle → 3.4 × 29.5735 = 100.55 ml, which is why the TSA limit is written as 3.4 oz / 100 ml. • A 16.9 fl oz water bottle → 499.79 ml, marketed as 500 ml outside the US.
When and why people use fluid ounces (us) to milliliters
Air travel is a surprisingly common trigger. Liquid restrictions are defined as 100 ml internationally and 3.4 fl oz in the US, and the two are the same limit expressed in different units — 3.4 fl oz is 100.55 ml, which is why containers marketed at exactly 3.4 oz sometimes fail a strict 100 ml reading. Cooking is the largest ongoing use. US recipes measure liquids in fluid ounces and cups while the rest of the world uses millilitres, and since the US cup is defined as 8 fl oz or 236.588 ml, converting a recipe means dealing with both units at once. Medicine dosing is the third and the one where accuracy matters most. Liquid medications are dosed in millilitres almost universally, but US household measures are in teaspoons and fluid ounces, and the mismatch is a documented source of paediatric dosing errors.
Common mistakes to watch for when converting fluid ounces (us) to milliliters
The US and imperial fluid ounce differ by about 4%: 29.5735 ml against 28.4131 ml. A UK recipe quoting fluid ounces converts differently from an American one, and a 20 fl oz imperial pint is 568 ml while a 16 fl oz US pint is 473 ml. Second, a fluid ounce measures volume and a weight ounce measures mass; they coincide only for water, so 8 fl oz of honey weighs considerably more than 8 oz. Third, the US legal cup used on nutrition labels is 240 ml rather than the 236.588 ml customary cup, a small difference that shows up when comparing a label against a recipe. Finally, avoid the 30 ml rounding for medication — at a 10 ml dose the error is small, but it compounds across repeated doses.
How to estimate fluid ounces (us) to milliliters in your head
Multiply by 30. For 8 fl oz: 8 × 30 = 240 ml against a true 236.6 — about 1.4% high, and conveniently the same as the 240 ml legal cup used on US nutrition labels. For a closer figure, multiply by 30 and subtract 1.5%. For 16 fl oz: 16 × 30 = 480, minus 7 gives 473 ml, matching the true 473.2. Anchors: 1 fl oz ≈ 30 ml, 3.4 fl oz ≈ 100 ml, 8 fl oz ≈ 237 ml, 12 fl oz ≈ 355 ml, 16 fl oz ≈ 473 ml. Note that a 12 fl oz US can is 355 ml while a European can is 330 ml — a 25 ml difference that is easy to miss and matters when scaling a drinks recipe from one market's packaging to the other's.
Fluid ounces (US) to Milliliters FAQ
How many ml is a US fluid ounce?
- Exactly 29.5735295625 ml, usually rounded to 29.57 ml.
Is the UK fluid ounce the same?
- No. The imperial fluid ounce is 28.4131 ml, about 4% smaller than the US one.
Why is the TSA limit 3.4 oz?
- Because 3.4 fl oz is 100.55 ml, which is how the international 100 ml limit is expressed in US units.
Is a fluid ounce the same as a weight ounce?
- No. One measures volume, the other mass. They only coincide for water — 8 fl oz of honey weighs far more than 8 oz.
How many ml in a US cup?
- 236.588 ml for the customary cup. Nutrition labels use a 240 ml legal cup instead.
Why is a UK pint bigger than a US pint?
- A UK pint is 20 imperial fluid ounces (568 ml); a US pint is 16 US fluid ounces (473 ml).
Can I round to 30 ml?
- For rough cooking, yes. For medication no — the error compounds across repeated doses.
Does the tool send my values anywhere?
- No. Everything is computed locally.
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Sources: NIST Handbook 44 on US customary liquid measure; UK Weights and Measures Act for the imperial fluid ounce; FDA labelling regulations defining the 240 ml legal cup; TSA liquids rule (3.4 oz / 100 ml).