Does 30 mL equal 1 oz?

There is often confusion around liquid measurements in cooking, especially when converting between metric units like milliliters (mL) and imperial units like ounces (oz). Understanding the relationship between mL and oz is important for accurately following recipes and getting the right results.

Quick Answer

No, 30 mL does not equal exactly 1 oz. However, 30 mL is very close to 1 oz in volume. Here is a quick overview of the mL to oz conversion:

  • 1 oz = 29.57 mL
  • 30 mL = 1.01 oz

So while 30 mL is close to 1 oz, it is slightly more. The exact conversion factor is 1 oz = 29.57 mL.

mL to oz Conversion

Let’s look at the mL to oz conversion in more detail.

Milliliters and Ounces Units

  • mL or milliliters – a unit of volume in the metric system
  • oz or ounces – a unit of volume in the imperial system

Conversion Factor

The exact conversion factor between these two units is:

  • 1 oz = 29.57 mL

This means:

  • There are 29.57 mL in 1 oz
  • To convert from oz to mL, multiply the number of oz by 29.57
  • To convert from mL to oz, divide the number of mL by 29.57

Let’s look at some examples:

Ounces Milliliters
1 oz 29.57 mL
2 oz 59.14 mL
0.5 oz 14.79 mL

So while 30 mL is very close to 1 oz in volume, it does not equate exactly. The exact conversion is:

  • 30 mL = 1.01 oz

Comparing 30 mL and 1 oz

Looking at a side-by-side comparison of 30 mL and 1 oz makes it easier to see the slight difference:

Volume Milliliters Ounces
30 mL 30 mL 1.01 oz
1 oz 29.57 mL 1 oz

So 30 mL equates to 1.01 oz, which is 0.43 oz more than 1 oz exactly. That 0.43 oz difference seems small, but can make a difference in recipes when precision is vital.

Why the Confusion?

Many people understandably assume 30 mL is the same as 1 oz. Here are some reasons why the close volumes create confusion:

  • Rounding – 30 mL rounds to 1 oz when rounding to the nearest whole number
  • Common Equivalents – In cooking, 30 mL and 1 oz are often used interchangeably
  • Simple Conversion – 30 is easy to remember and convert in your head

However, even though they are very close, the volumes are not exactly the same. Being aware of the precise conversion factor can make a big difference in accurately following recipes.

Does the Difference Matter?

Whether the slight difference between 30 mL and 1 oz matters depends on the context:

  • For estimated measurements when cooking, 30 mL and 1 oz can generally be used interchangeably without issue.
  • For precision recipes like baking, the slight difference could impact the end result. Accuracy is vital.
  • When converting measurements in recipes, the precise conversion factor should be used.

So in casual cooking, 30 mL and 1 oz are essentially equal. But for precise recipes or measurement conversions, be aware they are not exactly the same.

Tips for Converting mL and oz

Here are some tips when working with mL and oz conversions:

  • Use the exact conversion factor: 1 oz = 29.57 mL
  • Don’t rely on the 30 mL = 1 oz equivalence for conversions
  • For baking recipes, use a scale for the most accurate measurements
  • When converting, calculate using the precise mL and oz amounts
  • If a recipe calls for 30 mL, use 30 mL instead of 1 oz
  • Round to the nearest mL or oz after converting, instead of before

Following these tips will ensure you get the most accurate results when converting between milliliters and ounces.

How Are mL and oz Used?

Knowing the typical uses for mL and oz can also help avoid confusion:


  • Used in the metric system which is common internationally
  • Precise measurements in pharmacy and chemistry
  • Measuring liquids like water, juices, stocks, wines
  • Enumerating small amounts of ingredients


  • Used in the imperial system like in the US
  • Measuring heavier ingredients like meat, cheese, nuts
  • Measuring thick liquids like honey, batter, cream
  • Serving sizes – “1 oz” of a food item

Understanding the common uses provides context on when each unit is typically called for.


While 30 mL and 1 oz are very close in volume, they are not exactly equal. The conversion factor to keep in mind is:

  • 1 oz = 29.57 mL

This precise conversion is important for recipes that require accurate measurements. However, for casual everyday cooking, 30 mL and 1 oz can generally be used interchangeably without issue. Being aware of the slight difference can help prevent confusion and ensure your recipes turn out right.


Leave a Comment