Concentration Mathematics Guide

Concentration tells you how much of a substance is in each millilitre of a solution. This guide covers the arithmetic only and is not medical advice.

What the calculation means

Concentration is a ratio: amount divided by volume. Two solutions can contain the same amount but have different concentrations if their volumes differ.

The formulas

Concentration = amount ÷ volume.
Amount = concentration × volume.
Volume = amount ÷ concentration.
mg/mL × 1000 = mcg/mL.

Worked example (mathematical example only)

10 mg in 4 mL: 10 ÷ 4 = 2.5 mg/mL, which is 2500 mcg/mL. At that concentration 1 mL holds 2.5 mg, and 0.1 mL holds 0.25 mg (250 mcg).

More liquid, lower concentration

The same 10 mg in 8 mL gives 1.25 mg/mL, half the concentration. The amount did not change; only the volume did.

Common mistakes

Reading mg/mL as mcg/mL, a factor of 1000.
Using the vial amount in mcg with a volume formula built for mg.
Forgetting that the result depends on the exact volume entered.

Concentration calculator · Solution concentration calculator · Reconstitution guide

Mathematical calculation only. Not medical advice.