Does 64 ounces equal 2 liters?

Whether 64 ounces is equal to 2 liters is a common question for those needing to convert between U.S. customary units and metric units. The short answer is yes, 64 fluid ounces is equal to exactly 2 liters. However, to fully understand the relationship between these two units of volume, it’s important to break things down further.

The Definition of Ounces and Liters

An ounce is a unit of volume in the U.S. customary system. One U.S. fluid ounce is defined as exactly 1/128 of a U.S. gallon. A liter is a unit of volume in the metric system. One liter is defined as exactly 1/1000 of a cubic meter.

To determine if 64 ounces equals 2 liters, we need to look at the formal definitions of a U.S. gallon and a cubic meter:

  • 1 U.S. gallon = 231 cubic inches exactly
  • 1 cubic meter = 1,000,000 cubic centimeters exactly

Converting 64 Ounces to Liters Step-by-Step

Using the above definitions, we can now show the conversion from 64 ounces to liters step-by-step:

  1. Start with 64 fluid ounces.
  2. Convert ounces to cubic inches by multiplying by 1.8046875 cubic inches per fluid ounce (because 1 gallon = 128 fluid ounces):
    • 64 oz x 1.8046875 in3/oz = 115.5 in3
  3. Convert cubic inches to cubic centimeters by multiplying by 16.387064 cm3/in3 (the conversion factor between in3 and cm3):
    • 115.5 in3 x 16.387064 cm3/in3 = 1,892.5 cm3
  4. Convert cubic centimeters to liters by dividing by 1,000 cm3/liter:
    • 1,892.5 cm3 / 1,000 cm3/liter = 1.8925 liters

Therefore, 64 fluid ounces is equivalent to 1.8925 liters. Since liters are typically measured to the nearest 0.001 liters, we can round this to 1.893 liters. For all practical purposes, 64 fluid ounces is equal to 2 liters. The conversion factor between fluid ounces and liters is:

  • 1 fluid ounce = 0.0295735 liters

More Examples and Table

To further illustrate that 64 fluid ounces is essentially equivalent to 2 liters, here are some more examples:

  • 128 oz = 3.79 liters (rounds to 3.79 liters)
  • 192 oz = 5.68 liters (rounds to 5.68 liters)
  • 256 oz = 7.57 liters (rounds to 7.57 liters)

This pattern continues where increments of 64 fluid ounces increase the liter measurement by approximately 2 liters. The exact conversion figures are summarized in this table:

Fluid Ounces Liters Rounded Liters
64 oz 1.8925 1.893
128 oz 3.7850 3.785
192 oz 5.6775 5.678
256 oz 7.5700 7.570

Why 64 Ounces Equals 2 Liters

Now that we’ve clearly shown through conversion factors and examples that 64 fluid ounces is practically equal to 2 liters, let’s discuss why this relationship exists in the first place.

It comes down to the definitions and origins of the U.S. customary system compared to the metric system. The U.S. customary system of measurement started in the British Empire in the 18th century. Many of its units were defined in relation to old English units of measurement. The U.S. later formalized its own customary units in the 19th century, basing them on the British definitions.

The metric system was established in the 1790s in France, engineered to create a universal, standard system of measurement. Metric units are based on consistent base ten prefixes, with conversions between units simplified by factors of 10s, 100s, 1000s, etc. The liter was designed to be 1 cubic decimeter, elegantly relating volumes to the meter unit of length.

When comparing U.S. fluid ounces to liters, we are relating two different systems with unrelated origins. The facts that a U.S. gallon happens to be close to 231 cubic inches and that conversion between cubic inches and centimeters yields a factor close to 16 are coincidences, not designed relationships. The neat power-of-10 relationship between liters and cubic meters is inherent to the metric system, while the ounce/gallon/inch relationship arose from customary units’ organic origins.

Converting Between Liters and Ounces

Now that we have confirmed that 64 fluid ounces is essentially equivalent to 2 liters, how can we use this relationship for converting any number of fluid ounces to liters, and vice versa?

The key is the conversion factor between the two units:

  • 1 fluid ounce = 0.0295735 liters

To convert fluid ounces to liters, multiply fluid ounces by 0.0295735. For example:

  • 128 fl oz x 0.0295735 L/fl oz = 3.7850 L
  • 56 fl oz x 0.0295735 L/fl oz = 1.6562 L

To convert liters to fluid ounces, divide liters by 0.0295735. For example:

  • 5 L / 0.0295735 fl oz/L = 169 fl oz
  • 2.5 L / 0.0295735 fl oz/L = 84.5 fl oz

So for any conversion between fluid ounces and liters, apply the appropriate math operation using the conversion factor 0.0295735. This allows conversions in either direction using the relationship between 64 fluid ounces and 2 liters.

Converting Between Common Ounce and Liter Volumes

Certain fluid ounce and liter values are commonly used and converted. Here is a quick reference guide for some of the most common conversions:

  • 1 liter = 33.81 fluid ounces
  • 2 liters = 67.63 fluid ounces
  • 4 liters = 135.26 fluid ounces
  • 8 liters = 270.52 fluid ounces
  • 16 liters = 541.03 fluid ounces
  • 16 fluid ounces = 0.47 liters
  • 32 fluid ounces (1 quart) = 0.95 liters
  • 64 fluid ounces (1/2 gallon) = 1.89 liters
  • 128 fluid ounces (1 gallon) = 3.79 liters

Memorizing some of these common conversions can make translating between fluid ounces and liters quicker and easier.

When to Use Liters vs. Ounces

Now that we’ve thoroughly covered the conversion between fluid ounces and liters, when should you use each unit? Here are some guidelines:

  • Liters – Use liters when doing calculations in the sciences, medicine, and industries that typically use the metric system. Liters are also common for bottled beverage volumes internationally. Use liters for formal scientific contexts.
  • Fluid ounces – Use fluid ounces for cooking measurements in the U.S., as recipes are typically written using cups, tablespoons, fluid ounces, etc. Also use fluid ounces for consumer products sold with fluid volume in the U.S.

For a frame of reference on everyday volumes:

  • 12 fl oz = soda can volume
  • 16 fl oz = water bottle volume
  • 24 fl oz = large soda bottle volume
  • 2 L = medium soda bottle volume internationally

Choose ounces or liters depending on your particular application and context.


In summary, 64 fluid ounces is essentially equivalent to 2 liters. The exact conversion factor between fluid ounces and liters is 1 fl oz = 0.0295735 L. But the 2:64 relationship provides a nice round number ratio to remember.

Converting between fluid ounces and liters is straightforward using the 0.0295735 conversion factor and doing the appropriate math operations. Memorize some of the common conversions like 1 liter to 33.81 fl oz, or 64 fl oz to 1.89 liters to quickly translate values.

Use fluid ounces for cooking, product volumes, etc. in the U.S. Use liters for science, medicine, and international products. Consider the context when choosing ounces or liters to represent a volume.

So the next time you need to know if 64 ounces equals 2 liters, you now understand why this convenient relationship exists and how to apply it to any conversion between the two units.

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