Fluid Ounces: US vs Imperial
Mesmo Name, Diferente Volumes
Learn o DifferenceO fluid ounce might seem like a simples medição, but it comes in two confusingly diferente sizes. A US fluid ounce é slightly larger than an imperial fluid ounce—yet a US cup (8 fl oz) é smaller than an imperial cup (10 fl oz). Este guia untangles o fluid ounce confusion.
Side-by-Side Comparison
| Attribute | US Fluid Ounce | Imperial Fluid Ounce |
|---|---|---|
| Volume | 29.57 mL | 28.41 mL |
| Relationship to pint | 16 fl oz = 1 pint | 20 fl oz = 1 pint |
| Relationship to gallon | 128 fl oz = 1 gallon | 160 fl oz = 1 gallon |
| Símbolo | fl oz (US) | fl oz (imp) |
| Usado in | United States | UK, Canada, Ireland |
Por que Are They Diferente?
O split traces back to 1824 quando Britain reformed its medição sistema. Before esse, ambos countries usado similar fluid ounces. Aqui's o que happened:
O US Fluid Ounce
Derived from o wine gallon esse o American colonies usado. O US gallon (128 fluid ounces) foi definido as 231 cubic inches, making cada US fluid ounce sobre 1.8 cubic inches.
O Imperial Fluid Ounce
Quando Britain created o imperial sistema in 1824, they definido o gallon as o volume of 10 pounds of water. Este larger gallon (160 fluid ounces) tem a slightly smaller individual fluid ounce.
Tabela de Conversão
| US Fluid Ounces | Imperial Fluid Ounces | Milliliters |
|---|---|---|
| 1 US fl oz | 1.041 imp fl oz | 29.57 mL |
| 8 US fl oz (1 cup) | 8.33 imp fl oz | 236.6 mL |
| 16 US fl oz (1 pint) | 16.65 imp fl oz | 473.2 mL |
| 32 US fl oz (1 quart) | 33.31 imp fl oz | 946.4 mL |
| 128 US fl oz (1 gallon) | 133.2 imp fl oz | 3,785 mL |
Conversão Formulas
US to Imperial
Imperial fl oz = US fl oz × 1.0408
Exemplo: 12 US fl oz × 1.0408 = 12.49 imperial fl oz
Imperial to US
US fl oz = Imperial fl oz × 0.9608
Exemplo: 12 imperial fl oz × 0.9608 = 11.53 US fl oz
Either to Métrico
- US fl oz to mL: Multiply by 29.57
- Imperial fl oz to mL: Multiply by 28.41
- mL to US fl oz: Divide by 29.57
- mL to Imperial fl oz: Divide by 28.41
Prático Implications
Culinária e Recipes
A maioria recipes don't specify qual fluid ounce they mean. Rules of thumb:
- American recipes use US fluid ounces
- British recipes may use imperial fluid ounces (but increasingly use métrico)
- For small amounts, o 4% difference é negligible
- For large batches, use métrico (mL) for clarity
Beverage Bottles
Bottle sizes often differ entre countries:
| Product | US Market | UK Market |
|---|---|---|
| "12 oz" soda | 355 mL (12 US fl oz) | 330 mL (typical) |
| Beer pint | 473 mL (16 US fl oz) | 568 mL (20 imp fl oz) |
| Wine bottle | 750 mL (padrão) | 750 mL (padrão) |
Fluid Ounces vs Peso Ounces
Don't confuse fluid ounces (volume) com regular ounces (weight). They measure diferente things:
- Fluid ounce: Measures volume (como much space something takes up)
- Ounce (oz): Measures weight/mass (como heavy something é)
For water, 1 US fluid ounce weighs almost exatamente 1 avoirdupois ounce—but este é a coincidence esse doesn't hold for outro liquids. Honey, oil, e alcohol têm diferente densities, so their weight per fluid ounce varies.
Onde Cada Is Usado Hoje
US Fluid Ounces
- United States (beverages, culinária, medicine)
- US food exports
- Alguns Latin American countries
Imperial Fluid Ounces
- United Kingdom (decreasing use)
- Canada (mainly for beer)
- Ireland
- Alguns Caribbean nations
Métrico (A maioria of o Mundo)
A maioria countries use milliliters exclusively. Mesmo o UK e Canada têm largely transitioned to métrico for cotidiano use, keeping fluid ounces mainly for beer e traditional recipes.
Conclusão
O US e imperial fluid ounces são close enough esse small medições são interchangeable, but o 4% difference adds up in larger quantities. Quando precision matters—ou quando trabalhando com international recipes—converter to milliliters for clarity.
Remember: o US fluid ounce é larger (29.57 mL vs 28.41 mL), but lá são fewer of them in a gallon (128 vs 160).