When looking at liquid measurements, it can be confusing to determine if one unit in one system of measurement is the same as a unit in another system of measurement. Specifically, people often wonder if 100ml is the same amount as 3.4 oz. The short answer is yes, 100ml is essentially the same as 3.4 oz when measuring liquids. However, let’s take a deeper look at comparing metric and US customary units of volume to fully understand the conversion.
Metric System Overview
The metric system is used for measurement throughout most of the world. It is based on a decimal system with standard units for length, volume, and mass. For any given measurement, the prefixes milli-, centi-, deci- etc. represent fractions while prefixes like deca-, hecto-, and kilo- represent multiples.
For volume, the standard base unit in the metric system is the liter (L). Common fractions of a liter include:
- Milliliter (mL) = 1/1000 of a liter
- Centiliter (cL) = 1/100 of a liter
- Deciliter (dL) = 1/10 of a liter
So 100mL represents 100 milliliters or one hundredth (1/100) of a liter. The milliliter is a commonly used unit for measuring the volume of small amounts of liquids like medications, liquors, and flavored extracts.
US Customary System Overview
The US customary system of measurement is used predominately in the United States. It is similar to the imperial system used broadly in the British Commonwealth countries. Units of volume in the US customary system include:
- Gallon (gal)
- Quart (qt) = 1/4 gallon
- Pint (pt) = 1/2 quart = 1/8 gallon
- Fluid ounce (fl oz) = 1/16 pint = 1/128 gallon
- Teaspoon (tsp) = 1/6 fl oz
- Tablespoon (tbsp) = 3 tsp = 1/2 fl oz
As you can see, a fluid ounce is 1/128 of a gallon. So 3.4 fl oz represents 3 and 4/16 fluid ounces.
Converting Between Milliliters and Ounces
Now that we’ve reviewed the metric and US customary systems of volume measurement, how exactly do we convert between milliliters (mL) and fluid ounces (fl oz)? Here are some key facts that allow us to convert between the two units:
- 1 liter = 1000 mL
- 1 liter = 33.814 fl oz
- 1 fl oz = 29.5735 mL
Using these conversion factors, we can calculate:
100 mL x (1 fl oz / 29.5735 mL) = 3.3814 fl oz
And conversely:
3.4 fl oz x (29.5735 mL / 1 fl oz) = 100.5 mL
So while not exact, 100 mL is essentially equivalent to 3.4 fl oz when measuring liquids. The slight variation between the converted numbers is due to rounding during the conversions. But for all practical purposes in cooking, baking, mixing drinks, and other everyday situations, 100 mL and 3.4 fl oz can be used interchangeably.
Examples Comparing 100 mL to 3.4 fl oz
To illustrate that 100mL and 3.4 fl oz represent the same volume, here are some examples:
- The recommended single serving of cough syrup is often 30 mL or 1 fl oz.
- Many shot glasses hold approximately 45 mL or 1.5 fl oz.
- There are about 200 sprays in a 100 mL bottle of spray perfume. A 3.4 oz bottle would contain a similar amount.
- A standard wine bottle is 750 mL which is approximately 25.4 oz.
So whether referring to milliliters or fluid ounces, the practical volume is essentially the same. Just keep in mind:
- 100 mL = 3.4 fl oz
- 3.4 fl oz = 100 mL
when approximating liquid volumes between the metric and US customary systems.
Converting Other Volumes Between mL and fl oz
We’ve established that 100 mL is essentially equivalent to 3.4 fl oz. But what about converting other volumes between mL and fl oz? Here are some common liquid measurements converted:
Milliliters | Fluid Ounces |
---|---|
10 mL | 0.34 fl oz |
50 mL | 1.7 fl oz |
150 mL | 5.1 fl oz |
250 mL | 8.5 fl oz |
350 mL | 11.8 fl oz |
500 mL | 16.9 fl oz |
750 mL | 25.4 fl oz |
1000 mL | 33.8 fl oz |
To convert any milliliter amount to fluid ounces, simply multiply the number of mL by 0.034 to get an approximate value in fl oz. For even more precise conversions, use the factor 1 fl oz = 29.5735 mL.
Converting Common Cooking Measurements
In cooking recipes, the abbreviations mL and fl oz are often used interchangeably, especially for volumes under 1 cup. Here are some examples of approximate conversions for common cooking measurements:
Milliliters | Fluid Ounces | Common Cooking Equivalent |
---|---|---|
15 mL | 0.5 fl oz | 1 tablespoon |
30 mL | 1 fl oz | 2 tablespoons |
60 mL | 2 fl oz | 1/4 cup |
80 mL | 2.7 fl oz | 1/3 cup |
125 mL | 4.2 fl oz | 1/2 cup |
240 mL | 8 fl oz | 1 cup |
So when a recipe calls for 1/4 cup of milk which is equivalent to about 60 mL, you can also measure out 2 fl oz with reasonable accuracy.
Tips for Accurately Measuring Liquids
When measuring liquids for cooking, baking, mixing drinks, and other purposes:
- Use clear measuring cups with volume markings – this allows you to see the liquid level accurately.
- View at eye level – looking at the liquid amount from above or below can distort the reading.
- Use the right size vessel – measure small amounts in cups marked with tablespoons or ounces to improve precision.
- Read at the bottom of the meniscus – the curved upper surface of the liquid. This compensates for the liquid clinging to the cup.
- Avoid over or under pouring – this can happen when hastily filling a large volume all at once. Pour slowly and watch the markings.
- Repeat measurements if unsure – double check amounts if a recipe seems off. Small measuring errors can have big impacts on baking chemistry.
Adopting good measuring techniques helps ensure accuracy whether you are using metric or US customary liquid volumes.
Why Different Volume Measurement Systems Exist
With metric being the dominant global standard, why does the US still largely rely on US customary units like cups, tablespoons, and fluid ounces for liquid volumes? Here is some background on the history of measurement systems that sheds light on this question.
Back in the 10th century, the first reference to Ancient English units of measurement was made in the laws of King Edgar the Peaceful. Over the following centuries, English units evolved and were later brought to America by colonists in the 17th and 18th centuries. The English system was formally adopted by the United States in 1832.
In contrast, the foundations of the modern metric system originated in France after the French Revolution in 1799. It was designed to be rational and universal, with interrelated units based on decimals. The use of metric was mandated in France and it eventually spread globally to become the most widely used system of measurement.
So the continued use of US customary units stems from centuries of tradition and familiarity. However, the US has officially been metric for many purposes since it adopted the Metric Conversion Act in 1975 in response to global standardization. Despite this, full adoption of metric in day to day life has been slow.
Cooking in America is one area that still leans heavily on US customary volumes like cups and spoons. The recipes passed down through generations as well as modern US cookbooks use these units. Food packaging aimed at US consumers also continues to use both US and metric volumes to maximize accessibility and ease of use.
So while metric dominates science, medicine, and industry in the US, the use of US customary units persists in the kitchen due to cultural tradition and familiarity. But both systems live side by side, especially for small volume liquid measurements under a liter or quart.
Why Converting Between mL and fl oz is Helpful
Understanding that 100 mL is essentially the same as 3.4 fl oz is useful any time you need to convert liquid volumes between metric and US customary units. Here are some examples of when converting mL and fl oz can be helpful:
- Following cooking recipes – Understanding that 30 mL is close to 1 fl oz helps when substituting different liquid measurements in recipes.
- Taking medication dosages – Knowing that 5 mL is approximately 0.17 fl oz allows you to take the correct amount of liquid medication whether the dosage instructions are in mL or fl oz.
- Mixing drinks – If a drink recipe calls for 1.5 oz of an ingredient but you only have a metric measuring spoon, you can use 45 mL instead.
- Shopping online – When an international online retailer describes product volumes in mL, converting to fl oz helps you understand the true amounts.
The ability to move between volume measurement systems grants flexibility which is increasingly useful in our globally connected world. Knowing that 100 mL is essentially the same amount as 3.4 fl oz is an easy conversion to memorize for everyday convenience.
Conclusion
In summary, while the metric system is the dominant global standard, the persistence of US customary units means that capacities may be described in various volume units. Specifically, liquid volumes under 1 liter/quart are often represented in both milliliters and fluid ounces. But with 100 mL being essentially equivalent to 3.4 fl oz, you can move seamlessly between these common liquid volume measurements. So the next time you wonder if that 100 mL of liquid is the same as 3.4 oz, remember the handy conversion and that the answer is yes!