Short Answer 
Milligrams (mg) measure mass, while milliliters (mL) measure volume; converting between them requires knowledge of the substance’s density. The formula for conversion is milliliters = milligrams / density, and an example shows that with a density of 1 mg/mL, 500 mg equals 500 mL.
Understanding the Units
A milligram (mg) is a small unit of mass typically used to indicate the amount of an active ingredient in medications, while a milliliter (mL) is a unit of volume for measuring liquids. It’s important to recognize the difference between these two units, as they serve different purposes in medication dosages.
Conversion Basics
To convert milligrams to milliliters, the density of the substance in question must be known. Density is defined as the mass per unit of volume, typically expressed as milligrams per milliliter (mg/mL). The general formula for conversion is:
- Identify the density of the substance.
- Use the formula: milliliters = milligrams / density.
Example of Conversion
For practical application, if a medication has a density of 1 mg/mL, then 1 milligram equals 1 milliliter. To convert 500 mg to milliliters with this density:
- Divide 500 mg by the density 1 mg/mL.
- The result is 500 mL.
This simple approach can be applied to any medication once you are aware of its density.