If you’ve ever come across a recipe, manual, or packaging that states “1 ounce” and wondered how much an ounce is in millilitres, this article is for you.
It’s a very common question and, although it may seem simple, the answer depends on the measurement system being used.
In this article, we’ll unravel how to make the conversion correctly, discover how many ml are in an ounce, and provide you with a handy table you can refer to whenever needed.
How many millilitres are in an ounce?
When we talk about an “ounce” in the context of liquids, we’re usually referring to the fluid ounce (abbreviated as fl oz) rather than the ounce used for weight.
However, even within fluid ounces, there are two variants: the US fluid ounce and the British fluid ounce.
Types of fluid ounce
• US fluid ounce (US fl oz)
• Imperial or British fluid ounce (Imperial fl oz)
Common equivalence
• In the US system, 1 US fl oz is approximately equal to 29.5735 ml.
• In the British system, 1 Imperial fl oz is around 28.413 ml.
• In everyday use, especially in Spain, it’s common to round to 30 ml per fluid ounce to simplify calculations.
Therefore, when you wonder how much an ounce is, the most useful answer is: approximately 30 millilitres.
Why round to 30 millilitres?
In most domestic or culinary contexts, the difference between 29.6 ml and 30 ml is negligible.
However, if precision is required (for example, in cosmetics or laboratory use), it’s advisable to use the exact value.
All aboFluid ounce to millilitre conversion tableut the ounce
So you don’t need to calculate it each time, here’s a table with the most common conversion values:
| Ounces (fl oz) | Approximate Millilitres |
| 1 fl oz | ≈ 29.6 ml (≈ 30 ml) |
| 2 fl oz | ≈ 59.1 ml |
| 4 fl oz | ≈ 118.3 ml |
| 8 fl oz | ≈ 236.6 ml |
| 16 fl oz | ≈ 473.2 ml |
| 20 fl oz | ≈ 591.5 ml |
These values refer to the US fluid ounce. In the British system, they would be slightly lower (1 fl oz ≈ 28.4 ml).
When do you need to convert fl oz to ml?
International recipes
Cooking, cocktail, or baking recipes from Anglo-Saxon countries often use fluid ounces.
To adapt them to the metric system and maintain the correct proportions, it’s important to know how many ml are in an ounce and to use the indicated amount, even if it’s an approximation.
Product labelling
Many imported products, such as drinks or cosmetics, state their volume in ounces.
Knowing the equivalent allows you to better understand the actual quantity you are using or consuming.
Domestic or professional use
Whether you’re cooking at home or working in a technical setting, having a clear conversion helps avoid measurement errors and ensures accurate results.
Buying cups and containers for product sales
At Monouso, many disposable cups and containers are labelled in ounces, and knowing their millilitre equivalent will help you choose the right format for your drinks or food.
• A cup of 8 oz equals around 236 ml, ideal for coffee or medium soft drinks.
• A cup of 12 oz equals 355 ml, perfect for cold drinks or smoothies.
• A cup of 16 oz equals 473 ml, a common option for slushies, milkshakes or large juices.
With this information, you’ll be able to select the container size that best suits your business and your customers’ needs, optimising your purchases and providing a clearer, more professional experience.
How to convert ounces to millilitres easily
The formula for converting ounces to equivalent millilitres is very straightforward:
Millilitres = number of ounces × 29.5735
For example: if a recipe states 3 oz, the calculation would be 3 × 29.5735 = 88.7 ml — you could even round this to 90 ml.
When you wonder how much an ounce is, remember that its most practical equivalent is 30 millilitres, although the exact value in the US system is 29.5735 ml and in the British system 28.4 ml.
It’s also important to know how many millilitres are in a cup and the capacity of different types of cups.
Measuring with a cup is also very common when preparing recipes at home, which is why it’s helpful to know how many millilitres are in a cup.
Understanding the conversion from ounces to millilitres will enable you to adapt recipes, interpret labels, and measure liquids more accurately.
Now that you know what an ounce is equivalent to, you can apply this knowledge with confidence both in the kitchen and in any other situation where measurements matter.
Frequently Asked Questions (FAQs)
Is 1 ounce exactly 30 ml?
Not exactly. In fact, 1 US fluid ounce is equal to 29.5735 ml. However, rounding to 30 ml is common and practical for home use.
Can I always use 30 ml when I see “1 oz”?
Yes, unless you need absolute precision or are working with British measurements. In most recipes and product packaging, the US fluid ounce is the standard reference.
What if the recipe just says “oz” without specifying “fl oz”?
We have two options: use a jigger or a In that case, it’s worth checking the context, as “oz” may refer to either weight or volume. If the recipe includes liquids, it almost always refers to the fluid ounce.cup.
