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Fluid Ounces to Milliliters

1 US Fluid Ounce (fl oz) = 29.5735 Milliliter (ml)

Result
29.5735 ml
1 fl oz = 29.5735 ml

How Many Milliliters in a Fluid Ounce?

One US fluid ounce equals 29.5735 milliliters, commonly rounded to 30 ml for everyday use. To convert fluid ounces to milliliters, multiply the number of fluid ounces by 29.5735. This conversion appears constantly in daily life — from reading medicine dosage instructions and mixing cocktails to understanding travel container size limits and comparing beverage sizes internationally. The fluid ounce is used primarily in the United States and a few other countries, while most of the world measures liquid volumes in milliliters and liters. Knowing this conversion is particularly important for medication dosing, where precision can be critical, and for air travel, where the TSA enforces a 3.4 fluid ounce (100 ml) limit on carry-on liquids.

How to Convert US Fluid Ounce to Milliliter

  1. Identify the volume in US fluid ounces that you need to convert.
  2. Multiply the fluid ounce value by 29.5735 to get the precise milliliter equivalent.
  3. For quick mental math, multiply by 30. This overestimates by about 1.4%, which is negligible for most practical purposes.
  4. If working with Imperial fluid ounces (used in the UK), multiply by 28.4131 instead — the Imperial fluid ounce is slightly smaller than the US fluid ounce.
  5. Verify your result: a typical shot glass holds 1.5 fl oz (about 44 ml), and a standard soda can is 12 fl oz (about 355 ml).

Real-World Examples

Medicine dosing — A label says to take 2 fl oz of cough syrup
2 × 29.5735 = 59.15 ml. This is about 60 ml, which is typically four tablespoons. Many medicine cups are graduated in both fluid ounces and milliliters for exactly this reason.
Cocktail recipe — A recipe calls for 1.5 fl oz of vodka
1.5 × 29.5735 = 44.36 ml. This is a standard "jigger" or single shot in the US. European bars often pour 25 ml or 50 ml measures, so a US shot falls between the two.
Perfume bottle — A 3.4 fl oz bottle
3.4 × 29.5735 = 100.55 ml. The 3.4 fl oz / 100 ml size is not a coincidence — this is the maximum container size allowed in carry-on luggage by the TSA and ICAO regulations.
Travel containers — Packing toiletries for a flight
The TSA limit is containers of 3.4 fl oz (100 ml) or less. A typical travel-size shampoo is 3 fl oz = 88.72 ml, well under the limit. A regular shampoo bottle of 12 fl oz = 354.88 ml would need to go in checked luggage.
Baby bottle — A feeding of 6 fl oz of formula
6 × 29.5735 = 177.44 ml. Baby bottles sold internationally are usually marked in both fluid ounces and milliliters. The 180 ml mark on a metric bottle is the closest graduation.
Comparing beverage sizes — A US "tall" coffee is 12 fl oz
12 × 29.5735 = 354.88 ml, or about 355 ml. This is nearly identical to a standard 330 ml European soft drink can plus a small espresso shot — useful context when ordering coffee abroad.

Quick Reference

US Fluid Ounce (fl oz) Milliliter (ml)
1 29.5735
2 59.1471
5 147.868
10 295.735
25 739.338
50 1478.68
100 2957.35
500 14786.8
1,000 29573.5

History of US Fluid Ounce and Milliliter

The fluid ounce has a complicated history tied to the divergence between US and British measurement systems. The US fluid ounce is defined as 1/128 of a US gallon, which works out to exactly 29.5735295625 ml. The Imperial fluid ounce, used in the United Kingdom, is defined as 1/160 of an Imperial gallon, giving it a volume of 28.4130625 ml — about 4% smaller than its US counterpart. This difference arose because the US and British gallons are different sizes (3.785 liters vs. 4.546 liters) and are divided into different numbers of fluid ounces (128 vs. 160). The result is a confusing situation where a "fluid ounce" means slightly different things on different sides of the Atlantic. The milliliter, by contrast, has a single, unambiguous definition worldwide: one-thousandth of a liter, or equivalently, one cubic centimeter. The adoption of metric measurements for medication dosing has been a significant public health improvement, reducing errors caused by confusion between teaspoons, tablespoons, and fluid ounces. The American Academy of Pediatrics has recommended that all pediatric medications be dosed exclusively in milliliters to prevent dosing errors — a recommendation that has been widely adopted by pharmaceutical manufacturers.

Common Mistakes to Avoid

  • Confusing fluid ounces (a volume measure) with ounces (a weight measure). A fluid ounce of water weighs approximately 1.04 regular ounces (avoirdupois), but for other liquids the weight-to-volume relationship depends on density. Honey, for example, weighs significantly more per fluid ounce than water.
  • Using the Imperial fluid ounce conversion (28.41 ml) when working with US measurements (29.57 ml), or vice versa. The 4% difference can matter in precision contexts like medicine and chemistry.
  • Assuming the "ounce" on a food label always means fluid ounces. Solid foods are measured in weight ounces (avoirdupois), not fluid ounces. A 16 oz bag of chips weighs 16 ounces but does not occupy 16 fluid ounces of volume.
  • Forgetting the TSA liquid limit. The limit is 3.4 fl oz or 100 ml, whichever is printed on the container. A container labeled "4 fl oz" will be rejected even if it is only half full.
  • Rounding 29.57 ml to 25 ml. The correct quick approximation is 30 ml per fluid ounce, not 25. Using 25 ml underestimates by about 15%, which can cause significant errors in cooking and dosing.

Frequently Asked Questions

How many ml is 1 fluid ounce?
One US fluid ounce equals 29.5735 ml, commonly rounded to 30 ml. One Imperial fluid ounce (used in the UK) equals 28.4131 ml. For most practical purposes, the "roughly 30 ml" approximation works well.
How many fluid ounces is 100 ml?
100 ml equals 3.381 US fluid ounces, which is why the TSA travel limit is expressed as "3.4 fl oz or 100 ml." The two figures are equivalent within rounding.
What is the difference between US and Imperial fluid ounces?
A US fluid ounce is 29.5735 ml, while an Imperial fluid ounce is 28.4131 ml — the US fluid ounce is about 4% larger. This stems from the US and Imperial gallons being different sizes and divided into different numbers of fluid ounces (128 and 160, respectively).
How do I convert fluid ounces to tablespoons?
One US fluid ounce equals 2 US tablespoons. So 3 fl oz = 6 tablespoons, and 8 fl oz (1 cup) = 16 tablespoons. In milliliters: 1 US tablespoon = 14.79 ml, and 2 tablespoons = 29.57 ml = 1 fl oz.
Why is medicine measured in ml instead of fluid ounces?
Milliliters provide unambiguous, universal precision. Fluid ounces vary between US and Imperial systems, and household spoons (teaspoons, tablespoons) vary in actual volume. The American Academy of Pediatrics recommends ml-only dosing to reduce medication errors, especially for children. Most medicine cups and oral syringes are now marked exclusively in milliliters.
How many fl oz in a standard water bottle?
A standard single-serve water bottle is 16.9 fl oz (500 ml). Larger reusable water bottles commonly come in 24 fl oz (710 ml), 32 fl oz (946 ml, roughly 1 liter), and 40 fl oz (1,183 ml) sizes.
Quick Tip

For air travel, the key number to remember is 3.4 fl oz = 100 ml. When shopping for travel containers, look for bottles labeled "3 fl oz" or "100 ml" — both will be under the TSA limit. For cocktail making, a standard US jigger has a 1.5 fl oz (44 ml) side and a 0.75 fl oz (22 ml) side. And for quick kitchen conversions: 1 fl oz is about 2 tablespoons, 8 fl oz is 1 cup, and 16 fl oz is 1 pint.