Mass
The amount of matter in a substance or object. Common units include kg, g, mg and mcg (µg).
Scientific foundations
Understanding Mass, Volume, Concentration & Dose
Whether you are reading a nutrition label, reviewing research, comparing GLP-1 studies or learning about peptides, understanding basic measurement terminology makes scientific information easier to interpret.
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The four basics
Weight
Technically, the force gravity exerts on an object. Everyday health language commonly uses weight to mean body mass.
Volume
The three-dimensional space occupied by a substance. Common units include litres (L) and millilitres (mL).
Concentration
How much of a specified substance is present relative to a stated amount of a mixture or solution.
Concentration vs. dose
Concentration tells you what is in a solution. Dose tells you how much is administered. For a solution containing 5 mg/mL, the concentration remains 5 mg/mL whether the selected volume is 0.25 mL, 0.5 mL or 1 mL.
MASS ≠ VOLUME ≠ CONCENTRATION ≠ DOSE ≠ POTENCY
10 mg = total amount
2 mL = volume
5 mg/mL = concentration
0.5 mL = selected volume
2.5 mg = amount in that volume
Potency cannot be determined from these numbers alone.
Amount = concentration × volume. These relationships explain maths only; they do not determine what dose of a medication or investigational compound should be used.
Common ways concentration is expressed
- mg/mL
- Milligrams of a substance per millilitre of solution.
- mg/L
- Milligrams per litre, often used for more dilute solutions.
- mol/L
- Amount-of-substance concentration in moles per litre; commonly called molar concentration or molarity.
- % w/v
- Grams of substance per 100 mL of solution. 5% w/v means 5 g per 100 mL.
- % w/w
- Grams of substance per 100 g of total mixture.
- % v/v
- Millilitres of a liquid component per 100 mL of total mixture.
Strength can describe a total amount or a concentration depending on the product. Potency describes the amount or concentration needed for a biological effect and is not the same as either.
Interactive educational tool
Measurement & Concentration Lab
Explore mathematical relationships using hypothetical values. This lab does not check a product, prescribe a dose, establish sterility or replace a pharmacist.
Mass concentration
Concentration
5 mg/mL
Also
5,000 mcg/mL
Amount in selected volume
2.5 mg
This calculates a mathematical amount only. It does not recommend or verify a medication dose.
Unit conversions
0.001 g · 1 mg · 1,000 mcg
0.001 L · 1 mL
Dilution visualizer
10 mg in 1 mL
10 mg in 4 mL
Total amount stays
10 mg
Final volume
4 mL
New concentration
2.5 mg/mL
Mass, volume & density
Density = mass ÷ volume. Change either value to see why equal volumes do not always mean equal masses.
Density
5 g/mL
Standards and sources
Need another term? Open The Modern Health Dictionary.