Convert US fluid ounces to Imperial fluid ounces
1 US fluid ounce is 1.04 fl oz (UK). One US fluid ounce is exactly 1.04084273079 imperial fluid ounces.
One US fluid ounce is 1.0408427 imperial fluid ounces. To convert US fluid ounces to imperial fluid ounces, multiply by 1.0408427; to go the other way, divide by 1.0408427 or multiply by 0.96075994. The relation is exact but the figure is not: it is a rounding of a number that does not terminate, and it follows from NIST Handbook 130. Exactly one 128th of a US gallon, which makes it 29.5735295625 ml exactly.
Factor checked against the defining standard · How we check
- US fluid ounces × 1.0408427
1 * 1.04084271.041 fl oz (UK)
1 US fluid ounce in every volume unit
| Unit | Value | Exact factor |
|---|---|---|
| US teaspoons | 6 tsp | × 6 |
| US tablespoons | 2 tbsp | × 2 |
| US fluid ounces (as entered) | 1 fl oz | — |
| US cups | 0.125 cup | × 0.125 |
| US pints | 0.0625 pt | × 0.0625 |
| US quarts | 0.03125 qt | × 0.03125 |
| US gallons | 0.0078125 gal | × 0.0078125 |
| milliliters | 29.57352956 ml | × 29.5735295625 |
| liters | 0.02957352956 L | × 0.0295735295625 |
| imperial gallons | 0.006505267067 gal (UK) | × 0.00650526706741 |
| imperial quarts | 0.02602106827 qt (UK) | × 0.0260210682697 |
| imperial pints | 0.05204213654 pt (UK) | × 0.0520421365393 |
| imperial fluid ounces | 1.040842731 fl oz (UK) | × 1.04084273079 |
| imperial gills | 0.2081685462 gi (UK) | × 0.208168546157 |
| cubic millimetres | 29,573.52956 mm³ | × 29,573.5295625 |
| cubic centimetres | 29.57352956 cm³ | × 29.5735295625 |
| cubic inches | 1.8046875 in³ | × 1.8046875 |
| cubic feet | 0.00104437934 ft³ | × 0.00104437934028 |
| cubic yards | 0.00003868071631 yd³ | × 0.0000386807163066 |
| cubic metres | 0.00002957352956 m³ | × 0.0000295735295625 |
Factors are entered by hand from NIST Handbook 130 rather than derived from a units library, so the ones that terminate are exact rather than rounded.
How do you convert US fluid ounces to imperial fluid ounces? The converter and the working
- 1.Take the measurement in US fluid ounces.
- 2.Multiply by 1.0408427 — that is how many imperial fluid ounces fit in one US fluid ounce.
- 3.To go back the other way, divide by 1.0408427, or multiply by 0.96075994.
Worked example: 25 US fluid ounces to imperial fluid ounces
- Formula
- fl oz × 1.0408427 = fl oz (UK)
- Arithmetic
- 25 × 1.0408427 = 26.02 fl oz (UK)
- Answer
- 25 fl oz = 26.02 fl oz (UK)
The factor is rounded for display; the figure above is computed from the full value.
US fluid ounces to imperial fluid ounces conversion table
| US fluid ounces | Imperial fluid ounces |
|---|---|
| 1 fl oz | 1.04 fl oz (UK) |
| 2 fl oz | 2.08 fl oz (UK) |
| 3 fl oz | 3.12 fl oz (UK) |
| 4 fl oz | 4.16 fl oz (UK) |
| 5 fl oz | 5.2 fl oz (UK) |
| 6 fl oz | 6.25 fl oz (UK) |
| 7 fl oz | 7.29 fl oz (UK) |
| 8 fl oz | 8.33 fl oz (UK) |
| 9 fl oz | 9.37 fl oz (UK) |
| 10 fl oz | 10.41 fl oz (UK) |
| 12 fl oz | 12.49 fl oz (UK) |
| 15 fl oz | 15.61 fl oz (UK) |
| 20 fl oz | 20.82 fl oz (UK) |
| 25 fl oz | 26.02 fl oz (UK) |
| 50 fl oz | 52.04 fl oz (UK) |
| 100 fl oz | 104.08 fl oz (UK) |
| 200 fl oz | 208.17 fl oz (UK) |
| 300 fl oz | 312.25 fl oz (UK) |
| 500 fl oz | 520.42 fl oz (UK) |
| 1000 fl oz | 1,040.84 fl oz (UK) |
| 2000 fl oz | 2,081.69 fl oz (UK) |
| 5000 fl oz | 5,204.21 fl oz (UK) |
| 10000 fl oz | 10,408.43 fl oz (UK) |
The imperial fluid ounce is the smaller one, against the run of play
The imperial gallon is larger than the US gallon, but the imperial fluid ounce is smaller: 28.4130625 ml against 29.5735295625. The imperial gallon divides into 160 fluid ounces and the US gallon into 128, and dividing a fifth more liquid into a quarter more parts leaves each part about 4% smaller. So a UK recipe asking for 10 fl oz means 284 ml and a US one means 296 ml.
NIST Handbook 44, Appendix C — general tables of units of measurement
What is a US fluid ounce?
Exactly one 128th of a US gallon, which makes it 29.5735295625 ml exactly. The imperial fluid ounce is a different unit at exactly 28.4130625 ml, so a UK recipe calling for 10 fl oz means 284 ml and a US one means 296 ml. It is also a volume, not a weight: an ounce of flour is not a fluid ounce of flour.
What is an imperial fluid ounce?
One 160th of an imperial gallon, 28.4130625 ml exactly. The US fluid ounce is one 128th of a smaller gallon at 29.57 ml, so the two ounces differ by about 4% in the opposite direction to the gallons.
How many imperial fluid ounces are in a US fluid ounce?
One US fluid ounce is 1.0408427 imperial fluid ounces. Going the other way, one imperial fluid ounce is 0.96075994 US fluid ounces. Both figures come from the same defined relation rather than from a measurement, which is why they are the same today as they were in 1959.
Every volume unit here
The whole group — 20 units with their symbols and the size of each one in liters — is on the conversion index, along with every pair it makes. The table above already gives each of them relative to a US fluid ounce.
Cite this page
- APA
- Rule Calculator. (2026). Convert US fluid ounces to imperial fluid ounces. Rule Calculator. https://rulecalculators.com/convert/fluid-ounce-to-imperial-fluid-ounce
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- "Convert US fluid ounces to imperial fluid ounces." Rule Calculator, August 16, 2026, https://rulecalculators.com/convert/fluid-ounce-to-imperial-fluid-ounce.
- Chicago
- Rule Calculator. "Convert US fluid ounces to imperial fluid ounces." Rule Calculator. Last reviewed August 16, 2026. https://rulecalculators.com/convert/fluid-ounce-to-imperial-fluid-ounce.
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Questions people actually ask
- How many imperial fluid ounces are in a US fluid ounce?
- 1.0408427. One 160th of an imperial gallon, 28.4130625 ml exactly. The US fluid ounce is one 128th of a smaller gallon at 29.57 ml, so the two ounces differ by about 4% in the opposite direction to the gallons.
- How do I convert imperial fluid ounces back to US fluid ounces?
- Divide by 1.0408427, or multiply by 0.96075994 — they are the same operation.
Other volume conversions
Imperial fluid ounces to US fluid ounces — the same conversion the other way.