Milliliters (mL) are a metric unit of volume. One milliliter is one-thousandth of a liter. It also is the equivalent of one cubic centimeter. To calculate the volume of an object in milliliters, you must first measure the object in centimeters and find the volume in cubic centimeters. If the object is defined by other units of measurement, you will have to convert the volume before you can find the milliliter volume.

Find the volume using the current units of measurement. For example, if the volume of a cylinder has a radius of 2 inches and a height of 6 inches, use the volume formula for cylinders: "pi * radius squared * height." Plug in the numbers to get or "3.14 * 2 inches * 2 inches * 6 inches," which give you a result of 74.4 cubic inches.

Convert the units of measurement of the volume to cubic centimeters if it is not already in cubic centimeters. You may need to consult a conversion table, which you can find online or in most dictionaries. To convert cubic inches to cubic centimeters, for example, you need to know that there are 16.387 cubic centimeters per cubic inch. In the above example where the cylinder contains 74.4 cubic inches, you would multiply 74.4 cubic inches by 16.387 cubic centimeters/cubic inch to get a result of 1,219 cubic centimeters.

The the units from cubic centimeters to milliliters, because one cubic centimeter equals one milliliter.