Concentration Calculator

Calculate concentration from mass, volume, molar mass, density, or dilution ratios.

Supports five calculation modes with metric and imperial units.

Updated September 2, 2026

CreatorFrank Zhao

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What is solution concentration?

Solution concentration describes how much dissolved substance (solute) is present in a given amount of solvent or total solution. It is one of the most fundamental measurements in chemistry, pharmacology, environmental science, and food production — because nearly every chemical process depends on how much of each ingredient is dissolved, not just what it is.

Different industries express concentration in different units. A pharmacist thinks in molarity (mol/L), a brewing chemist thinks in mass percent (w/w%), and a clinical lab may prefer mass-volume percent (w/v%). This calculator handles all five common formats in one place.

The five calculation modes available here cover every mainstream way to express and convert between concentration formats: mass-volume percent, mass percent, molarity, dilution calculations, and density-based conversion. The bidirectional engine means you can enter any two known values in a group and the calculator derives the third — no rearranging formulas by hand.

How to use this calculator

Each calculation mode presents a group of three related fields. Enter any two, and the third is solved automatically. You can switch units at any time using the dropdowns — the result updates instantly.

Choose a calculation mode

Use the radio buttons at the top to select the type of concentration you want to work with. The form fields update to match.

Enter the values you know

Fill in any two of the three fields in the selected group. Leave the unknown field blank — the calculator will solve for it.

Read the auto-calculated result

The solved field appears in blue and updates in real time as you edit any input. Switch units freely — no recalculation needed.

Worked example — mass-volume percent (w/v%)

You dissolve 5 g of sodium chloride in water and bring the total volume to 200 mL. What is the w/v% concentration?

\text{w/v\%} = \frac{m}{V \times 10}

=

\frac{5\ \mathrm{g}}{0.2\ \mathrm{L} \times 10}

=

2.5\%

The result means there are 2.5 grams of NaCl for every 100 mL of solution. In pharmacy and clinical chemistry, this is the standard way to express the strength of liquid preparations such as saline rinses or topical solutions.

Worked example — solution dilution

You have a stock solution at 2 M and need 1 L of a 1 M working solution. How much stock do you need?

C_1 V_1 = C_2 V_2

V_1 = \frac{C_2 V_2}{C_1}

=

\frac{1\ \mathrm{M} \times 1\ \mathrm{L}}{2\ \mathrm{M}}

=

0.5\ \mathrm{L}

Measure 0.5 L (500 mL) of the stock solution, then add solvent until the total volume reaches 1 L. The dilution mode also lets you work backwards — if you know the desired concentration and available stock volume, it tells you the final volume needed.

Formulas and variables

Mode 1 — Mass-volume percent (w/v%)

\text{w/v\%} = \frac{m_{\text{solute}}\ (\mathrm{g})}{V_{\text{solution}}\ (\mathrm{mL})} \times 100

Expresses grams of solute per 100 mL of solution. Common in pharmacy and clinical labs. Bidirectional — enter any two of mass, volume, or concentration to solve for the third.

Mode 2 — Mass percent (w/w%)

\text{w/w\%} = \frac{m_{\text{solute}}}{m_{\text{solution}}} \times 100

The ratio of solute mass to total solution mass, expressed as a percentage. Useful in industrial chemistry, food science, and environmental analysis where gravimetric measurements are more practical than volumetric ones.

Mode 3 — Molar concentration (molarity)

M = \frac{n}{V} = \frac{m}{M_w \times V}

Molarity ( $M$ ) is moles of solute per liter of solution. It ties mass, molar mass, and volume together. This mode links two relations: first converting mass to moles via molar mass, then dividing by volume. All three intermediate fields (mass, moles, molarity) are interconnected.

Where: $n$ = moles, $m$ = mass (g), $M_w$ = molar mass (g/mol), $V$ = volume (L)

Mode 4 — Solution dilution

C_1 V_1 = C_2 V_2

The dilution equation assumes the amount of solute stays constant when you add solvent. Enter any three of the four quantities — initial concentration, initial volume, desired concentration, or required final volume — and the calculator solves for the remaining one.

Mode 5 — Concentration from density

\text{wt/wt\%} = \frac{M \times M_w \times 100}{\rho}

When you know the solution density, molarity, and solute molar mass, this formula converts to mass-percent concentration. The density must be in g/L for this formula. A companion relation converts mass-percent to grams of solute per 100 g of water:

m_{\text{per 100g}} = \frac{P \times 100}{100 - P}

Tips and common mistakes

Watch your volume units in w/v%

The w/v% formula uses milliliters for volume. If you enter volume in liters, make sure the unit dropdown reflects that — the calculator handles the conversion automatically, but mixing units mentally is a common source of 1000× errors.

w/v% vs w/w% — they are not the same

Mass-volume percent measures mass per volume, while mass percent measures mass per mass. For dilute aqueous solutions the numbers are close, but for concentrated or dense solutions they can diverge significantly. Always check which unit your protocol requires.

Molarity depends on temperature

Because molarity is defined per volume of solution (not solvent), and solution volume changes with temperature, a 1.000 M solution at 20 °C will not be exactly 1.000 M at 37 °C. For temperature-sensitive work, consider molality (mol/kg solvent) instead.

Density-based conversion needs density in g/L

The density mode formula expects density in grams per liter. If you have g/mL (common for lab measurements), select the appropriate unit — the calculator converts internally, but entering a g/mL number into a g/L field will give a result that is off by a factor of 1000.

Mass percent cannot exceed 100%

If you enter solute mass greater than solution mass, the result exceeds 100% and is flagged as invalid. In practice, this means your input is physically impossible — check whether you swapped solute and solution masses.

Limitations

Ideal solution assumption: All formulas assume the solute dissolves completely and the solution behaves ideally — volume of solute plus solvent equals total solution volume. For non-ideal mixtures (e.g., ethanol in water), actual volumes may differ due to molecular interactions.
Temperature not modeled: Molarity and density-based conversions are temperature-dependent. The calculator uses the values you enter at face value without applying thermal expansion corrections.
Not for safety-critical dosing: While the math is accurate, this tool does not account for pharmacokinetics, bioavailability, patient weight, or drug interactions. For medical or pharmaceutical dosing, always consult a qualified professional.
Pure substances only: Molar mass inputs assume a single pure solute. For mixtures or solutions containing multiple solutes, use the mode that matches the dominant component or calculate each separately.

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