An imperial fluid ounce is 1/160 of an imperial gallon.
Imperial fluid ounces to Milliliters Converter — imp fl oz to mL
Convert Imperial fluid ounce (imp fl oz) to Milliliter (mL) using the exact conversion factor (1 imperial fluid ounce = 28.4130625 milliliter). See the formula, worked examples, conversion table, unit comparison, history, and common uses.
Imperial fluid ounces to Milliliters converter
Converter
Volume Converter
Convert metric, US customary, imperial, cooking, dry, and industrial volume units.
Context values
Some unit families need one extra value for a physically accurate result.
Milliliter is 0.001 liter units.
Result = input x 2.84130625e-5 / 1e-6.
Volume uses the cubic meter as the base unit.
Reserved above the conversion cards and below the converter.
About Converting Imperial fluid ounces to Milliliters
Imperial fluid ounce and Milliliter appear side by side at fuel pumps and on beverage labels, since the US measures liquids in gallons while most of the world uses liters. Imperial fluid ounce is typically associated with united Kingdom (historically; less common in current UK retail than metric units), while Milliliter is typically associated with standard small-volume unit worldwide.
Formula
milliliters = imperial fluid ounces × 28.4130625
This factor comes from each unit's defined relationship to the category's base unit: 1 imperial fluid ounce equals 0.0000284130625 base units, and 1 milliliter equals 0.000001 base units, so dividing one by the other gives the direct imperial fluid ounce-to-milliliter factor of 28.4130625.
Simple example
1 imp fl oz × 28.4130625 = 28.4130625 mL
1 imperial fluid ounce = 28.4130625 milliliters.
Real-world example
10 imp fl oz × 28.4130625 = 284.130625 mL
10 imperial fluid ounces = 284.130625 milliliters.
Conversion table
| Imperial fluid ounce (imp fl oz) | Milliliter (mL) |
|---|---|
| 1 imp fl oz | 28.4130625 mL |
| 5 imp fl oz | 142.0653125 mL |
| 10 imp fl oz | 284.130625 mL |
| 25 imp fl oz | 710.3265625 mL |
| 50 imp fl oz | 1,420.653125 mL |
| 100 imp fl oz | 2,841.30625 mL |
Reverse conversion: Milliliter to Imperial fluid ounce
28.4130625 mL × 0.03519507973 = 1 imp fl oz
28.4130625 milliliters = 1 imperial fluid ounces.
imperial fluid ounces = milliliters × 0.0351950797279
For a page dedicated to this direction, see Milliliter to Imperial fluid ounce.
Imperial fluid ounce vs. Milliliter
| Aspect | Imperial fluid ounce | Milliliter |
|---|---|---|
| Family | UK/imperial customary unit | SI derived (metric prefix) unit |
| Typical use | UK/Commonwealth beverage measurement in historical or specialized contexts | Medicine dosing (worldwide, including in the US) |
| Where it's used | United Kingdom (historically; less common in current UK retail than metric units) | Standard small-volume unit worldwide |
Understanding the Imperial fluid ounce
Imperial fluid ounce (imp fl oz) measures volume. The imperial fluid ounce is 1/160 of an imperial gallon: exactly 28.4130625 milliliters — slightly smaller than the US fluid ounce despite the larger imperial gallon, because it divides that gallon into more parts. It is classified as a UK/imperial customary unit.
Where it's used: United Kingdom (historically; less common in current UK retail than metric units)
Imperial fluid ounce vs. US fluid ounce. Confusingly, the imperial fluid ounce (28.41 mL) is slightly smaller than the US fluid ounce (29.57 mL), even though the imperial gallon is larger overall — because the imperial gallon is divided into 160 fluid ounces rather than the US gallon's 128.
Uses of the Imperial fluid ounce today
- UK/Commonwealth beverage measurement in historical or specialized contexts
History of the Imperial fluid ounce
The imperial fluid ounce follows from Britain's 1824 imperial gallon, divided into 160 parts rather than the 128 used in the US system, producing its counterintuitively smaller size relative to the US fluid ounce.
Historical origin. Imperial fluid ounce was not the invention of a single named person; it developed through the process described above.
Understanding the Milliliter
Milliliter (mL) measures volume. A milliliter is one-thousandth of a liter, equal to one cubic centimeter. It is classified as a SI derived (metric prefix) unit.
Where it's used: Standard small-volume unit worldwide
Uses of the Milliliter today
- Medicine dosing (worldwide, including in the US)
- Cooking and recipe measurement outside the US
- Beverage and small-container labeling
History of the Milliliter
The milliliter follows directly from the liter via the 'milli-' SI prefix. It is notable as one of the few metric units in routine US use, since medicine dosing (syringes, liquid medication) is specified in milliliters even in the US.
Historical origin. Milliliter was not the invention of a single named person; it developed through the process described above.
Imperial fluid ounce — sources
- UK Weights and Measures Act 1824 — Basis for the imperial fluid ounce via the imperial gallon.
Milliliter — sources
- BIPM SI Brochure — SI prefixes — Defines 'milli-' as the prefix for 10⁻³.
Reserved between the cards and the FAQ so the page stays balanced.
Frequently asked questions
How many milliliters are in 1 imperial fluid ounce?
1 imperial fluid ounce equals 28.4130625 milliliters, using the exact defined conversion factor rather than an estimate.
How do I convert imperial fluid ounce to milliliter?
Multiply the imperial fluid ounce value by 28.4130625. The converter above does this instantly to whatever precision you set.
How do I convert milliliter back to imperial fluid ounce?
Use the reverse factor: 1 milliliter equals 0.0351950797 imperial fluid ounces. You can also use the swap control in the converter above to flip the direction instantly.
What is a imperial fluid ounce?
Imperial fluid ounce (imp fl oz) measures volume. The imperial fluid ounce is 1/160 of an imperial gallon: exactly 28.4130625 milliliters — slightly smaller than the US fluid ounce despite the larger imperial gallon, because it divides that gallon into more parts. It is classified as a UK/imperial customary unit.
What is a milliliter?
Milliliter (mL) measures volume. A milliliter is one-thousandth of a liter, equal to one cubic centimeter. It is classified as a SI derived (metric prefix) unit.
Is the imperial fluid ounce to milliliter conversion exact?
Yes. The imperial fluid ounce is 1/160 of an imperial gallon: exactly 28.4130625 milliliters — slightly smaller than the US fluid ounce despite the larger imperial gallon, because it divides that gallon into more parts. That fixed definition is what the converter above uses, so any rounding you see is a display choice, not a limitation of the math.
What is the difference between imperial fluid ounce vs. us fluid ounce?
Confusingly, the imperial fluid ounce (28.41 mL) is slightly smaller than the US fluid ounce (29.57 mL), even though the imperial gallon is larger overall — because the imperial gallon is divided into 160 fluid ounces rather than the US gallon's 128.
Where is the imperial fluid ounce still used today?
United Kingdom (historically; less common in current UK retail than metric units)