Molarity Calculator

Solution chemistry · four calculation paths

Build the concentration you need

Start with mass or moles, choose the quantity you want to find, and keep every measurement in the unit that matches your lab work.

MassMolesVolumeConcentration

Calculation setup

Set up the calculation

Choose the result and unit, then enter the known values.

c = m ÷ (Mₘ × V)

Choose the unknownThe form reveals only the values this path needs.

Calculate

Result unit

More options · mass + molar mass

Solute provided as

Use direct moles only when the amount of solute is already known in mol, mmol, µmol, or nmol.

Known quantities

Enter your measurements

Enter each measured or specified quantity shown below.

Solute mass

Mass of solute only—not total solution mass.

Molar mass

Enter a known value; this tool does not parse chemical formulas.

Final solution volume

Use final total solution volume, not solvent volume added.

Chemistry preview. Formula paths and unit vectors are tested; independent chemistry review is still required before public release.

Solution composition

Build a concentration record that another scientist can reproduce

Molarity is more than a number followed by M. A defensible result identifies the chemical entity, converts mass to amount of substance when necessary, and uses the finished solution volume rather than the liquid poured in at the start.

Side-by-side guide · Solution composition

Three concentration languages that must not be blended

Defining relationship: c = n / V
Common laboratory unit: 1 M = 1 mol/L
Volume that belongs in V: Final mixture volume

Amount concentration
M, mM, µM, and nM express amount of substance per volume. Converting a weighed mass to these units requires molar mass; converting between metric prefixes does not.
Mass per volume
g/L, mg/L, and related units report solute mass per final mixture volume. They can be connected to molarity only when the correct molar mass is supplied.
Mass-fraction ppm or ppb
Mass fraction compares solute mass with total solution mass. This tool therefore asks for solution density when translating a mass fraction to a per-volume result; it does not silently equate ppm with mg/L.

Build a concentration record that another scientist can reproduce: The workbench supports several concentration families, but each describes a different quotient and needs different supporting data.

Name the species before doing the arithmetic

IUPAC defines amount concentration as the amount of a constituent divided by the volume of the mixture. The word constituent matters. One mole of NaCl formula units is not interchangeable with one mole of sodium ions, and a hydrate does not have the same molar mass as its anhydrous form. Record the exact formula, hydration state, purity basis, and lot information before entering a mass. This calculator deliberately does not infer a formula or look up a molar mass, because an apparently helpful guess could change the amount of substance.

When moles are already known, concentration is simply n divided by final volume. When a balance supplies mass, first calculate n = m / Mₘ, using a molar mass that describes the same entity as the weighed material. A label reported in milligrams can be normalized with the milligrams-to-micrograms converter, but that unit conversion does not establish identity, purity, or stoichiometry.

Three concentration languages that must not be blended

The workbench supports several concentration families, but each describes a different quotient and needs different supporting data.

Amount concentration

M, mM, µM, and nM express amount of substance per volume. Converting a weighed mass to these units requires molar mass; converting between metric prefixes does not.

Mass per volume

g/L, mg/L, and related units report solute mass per final mixture volume. They can be connected to molarity only when the correct molar mass is supplied.

Mass-fraction ppm or ppb

Mass fraction compares solute mass with total solution mass. This tool therefore asks for solution density when translating a mass fraction to a per-volume result; it does not silently equate ppm with mg/L.

From a bottle label to the calibration mark

Keep the unrounded values through the calculation and let the preparation method determine the reportable precision.

Normalize the measured quantities
Convert the entered mass, moles, molar mass, and volume to one coherent basis. If a protocol mixes millilitres and litres, the millilitres-to-litres calculator makes that decimal change explicit before the chemistry begins.
Dissolve, transfer, and bring to volume
Final volume is not the initial solvent charge. Dissolve the material, transfer quantitatively, rinse as the method requires, and then bring the solution to its final mark under the protocol's temperature conditions.
Document the prepared solution
Retain the unrounded calculation, measured mass, glassware class, preparation temperature, and final reported concentration. The calculator supplies arithmetic, not a certificate of calibration.

Know where the model stops

Activity and ionic strength are not calculated. At higher concentrations, chemical activity may be the quantity a thermodynamic model needs even when molarity is known.
Temperature-dependent expansion, solute purity, water of hydration, reaction yield, and dissociation are not corrected automatically.
Changing litres to another supported unit does not calibrate the vessel. Use the general unit converter only to translate a recorded capacity, not as a substitute for calibrated volumetric glassware.
A result based on a rounded label cannot acquire more significant information merely because the screen displays additional digits.

When the next task is making a working solution

Once the stock concentration is established, switch to the dilution calculator to determine how much stock belongs in a specified final volume. That tool conserves the selected concentration basis across C₁V₁ = C₂V₂; it does not recalculate molar mass or decide whether the proposed solvent is chemically compatible.

If the final container's capacity is still unknown, settle that geometry before choosing a target concentration. Separate the questions—what volume is available, what amount of solute is present, and what concentration basis the method requires—so that every number in the preparation record has one unambiguous meaning.

Important limitations

Volume means the final total solution volume, not solvent added. The calculator does not infer a compound, formula mass, purity, activity, density, temperature correction, reaction yield, or volume contraction; ppm and ppb are not silently treated as mg/L or µg/L.

Review the stated scope, calculation method, assumptions, supported inputs, and effective dates, and obtain qualified advice before using a high-stakes result.

This formula passed its registered engineering tests and is published under an explicit site-owner policy authorization. No independent expert, QA, editorial, legal, or third-party review is claimed. Verify consequential results with a qualified professional.

Solution composition

Build a concentration record that another scientist can reproduce

Side-by-side guide · Solution composition

Three concentration languages that must not be blended

Defining relationship: c = n / V
Common laboratory unit: 1 M = 1 mol/L
Volume that belongs in V: Final mixture volume

Amount concentration
M, mM, µM, and nM express amount of substance per volume. Converting a weighed mass to these units requires molar mass; converting between metric prefixes does not.
Mass per volume
g/L, mg/L, and related units report solute mass per final mixture volume. They can be connected to molarity only when the correct molar mass is supplied.
Mass-fraction ppm or ppb
Mass fraction compares solute mass with total solution mass. This tool therefore asks for solution density when translating a mass fraction to a per-volume result; it does not silently equate ppm with mg/L.

Name the species before doing the arithmetic

Three concentration languages that must not be blended

The workbench supports several concentration families, but each describes a different quotient and needs different supporting data.

Amount concentration

M, mM, µM, and nM express amount of substance per volume. Converting a weighed mass to these units requires molar mass; converting between metric prefixes does not.

Mass per volume

g/L, mg/L, and related units report solute mass per final mixture volume. They can be connected to molarity only when the correct molar mass is supplied.

Mass-fraction ppm or ppb

From a bottle label to the calibration mark

Keep the unrounded values through the calculation and let the preparation method determine the reportable precision.

Normalize the measured quantities
Convert the entered mass, moles, molar mass, and volume to one coherent basis. If a protocol mixes millilitres and litres, the millilitres-to-litres calculator makes that decimal change explicit before the chemistry begins.
Dissolve, transfer, and bring to volume
Final volume is not the initial solvent charge. Dissolve the material, transfer quantitatively, rinse as the method requires, and then bring the solution to its final mark under the protocol's temperature conditions.
Document the prepared solution
Retain the unrounded calculation, measured mass, glassware class, preparation temperature, and final reported concentration. The calculator supplies arithmetic, not a certificate of calibration.

Know where the model stops

Activity and ionic strength are not calculated. At higher concentrations, chemical activity may be the quantity a thermodynamic model needs even when molarity is known.
Temperature-dependent expansion, solute purity, water of hydration, reaction yield, and dissociation are not corrected automatically.
Changing litres to another supported unit does not calibrate the vessel. Use the general unit converter only to translate a recorded capacity, not as a substitute for calibrated volumetric glassware.
A result based on a rounded label cannot acquire more significant information merely because the screen displays additional digits.