acalculator

What is the concentration?

Type how much solute you dissolved, its molar mass, and the volume (or mass) of the solution. The concentration calculator shows the concentration in every common unit at once.

Your numbers

Units
I know the solution’s
Molarity
0.839273

25.2 g of solute in 500 mL of solution is 0.839273 mol/L (5.04% by mass).

Mass concentrationg/L
50.4
Mass/volume percent% w/v
5.04
Mass percent% w/w
5.04
Parts per millionppm
50,400
Parts per billionppb
50,400,000
Molalitymol/kg
0.883817
Moles of solutemol
0.419636
Mass of solution
500 g
Volume of solution
500 mL

Molarity: 0.839273. 25.2 g of solute in 500 mL of solution is 0.839273 mol/L (5.04% by mass).

How to calculate

Computes the concentration of a solution as molarity, grams per litre, % w/v, mass percent, ppm, ppb and molality from the solute mass, its molar mass and the solution volume or mass.

Example with the default inputs (Mass of solute 25.2 g, Molar mass of solute (g/mol) 60.052, I know the solution’s Volume, Volume of solution 0.5 L, Density of solution 1 g/mL): 25.2 g of solute in 500 mL of solution is 0.839273 mol/L (5.04% by mass).

Method: moles = mass ÷ molar mass; molarity = moles ÷ litres; g/L = grams ÷ litres; % w/v = grams ÷ mL × 100; mass percent = solute mass ÷ solution mass × 100; ppm = × 10⁶; ppb = × 10⁹; molality = moles ÷ (solution kg − solute kg).

  • The solution mass is volume × density (or the mass you type); its volume is mass ÷ density when you type the mass.
  • Dilute water solutions have a density close to 1 g/mL, the default.
  • Molality uses the solvent mass: the solution mass less the solute mass.

Machine-readable copies: Markdown, JSON.

Worked examples

Each example is checked against the calculator on every build.

  1. Mass of solute 25.2 g, Molar mass of solute (g/mol) 60.052, I know the solution’s Volume, Volume of solution 0.5 L, Density of solution 1 g/mL gives Molarity 0.839273, Mass concentration 50.4, Mass/volume percent 5.04, Molality 0.883817.Source: OpenStax Chemistry 2e, section 3.3, Molarity, Example 3.16: 25.2 g of acetic acid (60.052 g/mol) in 0.500 L is 0.839 M (https://openstax.org/books/chemistry-2e/pages/3-3-molarity, retrieved 2026-10-01)
  2. Mass of solute 0.00375 g, Molar mass of solute (g/mol) 180.156, I know the solution’s Mass, Mass of solution 5 g, Density of solution 1 g/mL gives Mass percent 0.075, Parts per million 750.Source: OpenStax Chemistry 2e, section 3.4, Other Units for Solution Concentrations, Example 3.22: 3.75 mg of glucose in 5.0 g is 0.075% by mass (https://openstax.org/books/chemistry-2e/pages/3-4-other-units-for-solution-concentrations, retrieved 2026-10-01)
  3. Mass of solute 0.0000045 g, Molar mass of solute (g/mol) 207.2, I know the solution’s Volume, Volume of solution 0.3 L, Density of solution 1 g/mL gives Parts per billion 15, Parts per million 0.015.Source: OpenStax Chemistry 2e, section 3.4, Example 3.25: 15 ppb of lead in 300 mL of water (density ~1.00 g/mL) is 4.5 µg (https://openstax.org/books/chemistry-2e/pages/3-4-other-units-for-solution-concentrations)

How it works

Type the mass of solute, its molar mass in g/mol, and either the volume or the mass of the whole solution, with the solution's density. The calculator converts everything to grams, litres and millilitres first. Then:

  • Solution mass = volume × density (when you type the volume); solution volume = mass ÷ density (when you type the mass).
  • Moles of solute = grams of solute ÷ molar mass.
  • Molarity (mol/L) = moles ÷ litres of solution.
  • Mass concentration (g/L) = grams of solute ÷ litres of solution. This is the same number as mg/mL.
  • Mass/volume percent (% w/v) = grams of solute ÷ millilitres of solution × 100.
  • Mass percent (% w/w) = solute mass ÷ solution mass × 100.
  • Parts per million (ppm) = solute mass ÷ solution mass × 1,000,000; parts per billion (ppb) × 1,000,000,000.
  • Molality (mol/kg) = moles ÷ kilograms of solvent, where the solvent mass = solution mass − solute mass.

Every concentration shows to 6 significant figures; the solution mass shows in grams (kilograms or pounds follow the unit system) and the volume in millilitres. The maths runs in floating point and each value is rounded half up for display only.

Rules

  • The solute mass and the solution mass are from 1 ng to 1,000 kg; the volume is from 1 nL to 1,000 m³ (1,000,000 L).
  • The molar mass is from 1 to 10,000,000 g/mol.
  • The density is from 0.1 to 25 g/mL (100 to 25,000 kg/m³). The default is 1 g/mL.
  • When the solute mass is the whole solution mass or more, there is no answer: "The solute weighs as much as the whole solution or more; check the masses, volume and density."
  • Unit conversions are exact: 1 mL = 0.000001 m³, 1 g/mL = 1,000 kg/m³, 1 oz = 28.349523125 g, 1 lb = 453.59237 g, 1 US fl oz = 29.5735295625 mL, 1 US gal = 3.785411784 L.

Worked examples by hand

Vinegar. 25.2 g of acetic acid (60.052 g/mol) in 0.500 L, density 1 g/mL. Moles = 25.2 ÷ 60.052 = 0.419636. Molarity = 0.419636 ÷ 0.500 = 0.839273 mol/L. Mass concentration = 25.2 ÷ 0.5 = 50.4 g/L; % w/v = 25.2 ÷ 500 × 100 = 5.04%. Solution mass 500 g, solvent 474.8 g, so molality = 0.419636 ÷ 0.4748 = 0.883817 mol/kg.

Glucose in spinal fluid. 3.75 mg (0.00375 g) in a 5.0 g sample. Mass percent = 0.00375 ÷ 5.0 × 100 = 0.075%; ppm = 0.00375 ÷ 5.0 × 1,000,000 = 750.

Lead in tap water. 4.5 µg in 300 mL at 1 g/mL, so the solution mass is 300 g. ppb = 0.0000045 ÷ 300 × 1,000,000,000 = 15 ppb = 0.015 ppm.

Other questions people ask

How do I calculate the concentration of a solution?

It depends on the unit. Molarity is moles of solute per litre of solution: 25.2 g of acetic acid (60.052 g/mol) is 0.41964 mol, and in 0.500 L that is 0.839 mol/L. Mass percent is the solute mass divided by the solution mass, times 100.

What is the difference between molarity and molality?

Molarity divides the moles of solute by the litres of solution. Molality divides them by the kilograms of solvent, which is the solution mass less the solute mass. Molality does not change with temperature, because it uses masses only.

How do I calculate mass percent?

Divide the mass of solute by the mass of the whole solution and multiply by 100. 3.75 mg of glucose in a 5.0 g sample is 0.00375 ÷ 5.0 × 100 = 0.075%.

What does ppm mean?

Parts per million by mass: the solute mass divided by the solution mass, times 1,000,000. For water at about 1 g/mL, 1 ppm is about 1 mg per litre. 4.5 µg of lead in 300 mL of water is 15 ppb, or 0.015 ppm.

What is % w/v?

Mass/volume percent: grams of solute per 100 mL of solution. Saline at 0.9% w/v has 0.9 g of sodium chloride in every 100 mL.

Why does the calculator ask for density?

Mass percent, ppm, ppb and molality need the mass of the solution, and molarity needs its volume. The density converts one to the other. Dilute water solutions are close to 1 g/mL, the default.