About

Converting mass (milligrams) to volume (milliliters) is a frequent task in medical settings and laboratories. However, this is not a direct 1:1 conversion unless the substance is water. The density of the liquid dictates the final volume. Syrups used in pediatrics are often denser than water, meaning 100mg of syrup occupies less volume than 100mg of water.

This tool provides preset densities for common medical and household liquids to ensure accuracy. Using a generic conversion factor for non-water substances can lead to dosage errors exceeding 20%, which is critical in pediatric or geriatric care where therapeutic windows are narrow.

Formulas

The conversion requires the density (ρ) of the specific substance.

V_(mL) = m_(mg)ρ_(mg/mL)

Note: 1 g/mL = 1000 mg/mL.

Reference Data

Substance	Density (g/mL)	100 mg equals
Water	1.00	0.1 mL
Alcohol (Ethanol)	0.789	0.127 mL
Cooking Oil	0.92	0.109 mL
Milk	1.03	0.097 mL
Glycerin	1.26	0.079 mL
Honey	1.42	0.070 mL
Mercury	13.53	0.007 mL
Gasoline	0.74	0.135 mL
Blood (Whole)	1.06	0.094 mL
Sea Water	1.025	0.098 mL

Frequently Asked Questions

No. This is only true for water at standard temperature (density approx 1 g/mL). For other substances, density plays a major role. For example, 1 mg of mercury is a much smaller volume than 1 mg of water.

Mass and volume are linked by density. Without knowing the density of the liquid (e.g., oil vs. water), it is mathematically impossible to convert milligrams to milliliters accurately.

Check the bottle label or the package insert. It is often listed in g/mL. If not listed, pharmacists typically assume a density close to water (1.0) for thin liquids, or higher (1.2-1.3) for thick syrups, but you should always consult a professional for medical dosages.

Only if you know the "bulk density" of the powder. However, powders pack differently depending on how tight they are compressed, so this conversion is less accurate for solids than for liquids.