Milligram per Cubic Centimeter (mg/cm³) – Definition, Formula, and Conversion Guide
Some density measurements involve very small samples — a bone fragment, a drug tablet, a thin polymer film — where kilograms and cubic meters feel far too large to be practical. The milligram per cubic centimeter solves this by scaling both mass and volume down together, keeping the numbers intuitive without changing the underlying physics. This guide explains what the unit means, how it relates to the SI base unit of density, and how to convert between them accurately.
What Is a Milligram per Cubic Centimeter?
A milligram per cubic centimeter measures how much mass, in milligrams, fits inside a volume of one cubic centimeter. It belongs to the family of density units, formed by combining a submultiple of the gram (the milligram) with a submultiple of the cubic meter (the cubic centimeter).
Why This Conversion Works
Density equals mass divided by volume. The SI base unit for density is kg/m³. One milligram equals 10⁻⁶ kilograms, and one cubic centimeter equals 10⁻⁶ cubic meters. When you divide mass by volume, these two factors of 10⁻⁶ cancel each other out exactly, which is why mg/cm³ and kg/m³ always share the same numeric value.
Density (mg/cm³) = Density (kg/m³) × 1
Conversion Formula
- kg/m³ to mg/cm³: no change — values are identical
- mg/cm³ to g/cm³: divide by 1,000
- mg/cm³ to kg/L: no change — values are identical
Milligram per Cubic Centimeter Conversion Table
| kg/m³ | mg/cm³ |
|---|---|
| 1 | 1 |
| 100 | 100 |
| 1,000 (water) | 1,000 |
| 1,850 (trabecular bone, approx.) | 1,850 |
| 2,700 (aluminum) | 2,700 |
Worked Examples
Example 1: A polymer sample has a density of 950 kg/m³. Express this in mg/cm³.
950 × 1 = 950 mg/cm³
Example 2: A bone sample measures 1.92 mg/cm³ in a lab report. Convert to g/cm³.
1.92 ÷ 1,000 = 0.00192 g/cm³
Common Use Cases
- Bone mineral density measurements in medical imaging
- Pharmaceutical formulation and tablet density testing
- Materials science for polymers, coatings, and thin films
- Laboratory-scale density measurements of small samples
Frequently Asked Questions
Is mg/cm³ the same as kg/m³?
Yes. Both units are numerically identical because their mass and volume scale factors cancel exactly.
Why use mg/cm³ instead of kg/m³?
Although the numeric value is the same, mg/cm³ is more intuitive in fields working with small physical samples, since the unit names match the scale of the material being measured.
How is density officially defined?
Density is defined by the International System of Units (SI) as mass per unit volume, with kg/m³ as the coherent SI unit. See the BIPM SI Brochure for the official reference.