Molarity Calculator

Updated Sep 2026 Used 5 times

Use the Molarity Calculator to calculate and interpret amount concentration.

Solve for

Choose a forward concentration calculation or a reverse preparation calculation.

Known solute amount

Choose whether the amount is known as mass or moles.

Amount of solute

Enter the amount of solute in moles or a supported submultiple.

Solute mass

Enter the mass of the exact solute form used.

Molar mass

Use the molar mass for the exact chemical form, including hydration where applicable.

Target molarity

Enter the target amount concentration for the preparation.

Final solution volume

Enter completed solution volume, not starting solvent volume.

Guest calculations stay on this device. Signed-in results sync privately.

Your result

Calculated molarity

Enter your values, then calculate to see a verified result.

Inputs usedReview the information used for this result.

Full calculation and sourcesReview the equation, normalized units, assumptions, and formula version.

Versioned calculationFormula v2.7.0

What is calculated

Molarity and, when mass is entered, mass concentration from the exact solute amount and final solution volume.

Supported inputs

Mass: g, mg or kg
Amount: mol, mmol or µmol
Volume: L, mL or µL

Important limitation

The denominator is final solution volume. The result does not determine safety, solubility, pH, activity, or reaction yield.

Normalize inputsConvert the entered units to mol, g, and L500.0 mL = 0.5000 L

Find molesUse entered moles or divide mass by molar massn = m / Mr

Divide by volumeUse completed solution volumec = n / V

Interpretation

The amount concentration is .

Moles are calculated from the entered amount before division by final volume.

Displayed decimals do not establish laboratory measurement accuracy.

Use this result

How to Calculate Molaritycheck the equation and unit sequence.How to Prepare a Molar Solutiontranslate a target concentration into required mass.M1V1 M2V2 Dilution Formulacontinue when working from an existing stock.

Molarity Calculator: purpose and method

Calculates amount concentration, amount of substance, and mass concentration from known solute amount, amount of solute, solute mass, and molar mass with visible method, validation, precision, and limitations.

Keep exploring

Method and test recordFormula v2.7.0

Recorded scope: formula, units, labels, validation, content package, and internal-route implementation
Publisher: CalculatorGeek
Reviewed by: CalculatorGeek Editorial Team
Recorded review date: 2026-09-20
Next source review: 2027-09-20
Definition fixtures: 8 configured scenarios
Published examples: 3 shown below

Recorded method

Formula identities, unit normalization, supplied acceptance cases, invalid boundaries, links, and rendered output are checked separately.

These records describe the published model and reference tests. A test-case count is not a certification of every possible input or an independent specialist review. Editorial policy

Known limitations

Final solution volume, not starting solvent volume, is the denominator.
Molar mass must match the exact chemical form used.
Purity, solubility, pH, activity, reaction yield, and chemical safety are outside this calculation.

Method sources

Latest model update

2026-10-10 - Completed missing semantic entities, relationships, answer targets, query themes, questions, and visible input/output meaning without changing the calculation model.

Reference inputs and expected results

These published examples are separate from the configured definition fixtures and any additional automated assertions. Expected values use the stated output units; invalid inputs are intended to be rejected.

Case	Inputs	Expected result
Main sodium chloride reference	{"basis":{"value":"mass"},"mass":{"value":5,"unit":"g"},"molar_mass":{"value":58.44,"unit":"g/mol"},"volume":{"value":500,"unit":"mL"}}	{"molarity":0.1711156742,"mass_concentration":10}
Mass and volume unit equivalence	{"basis":{"value":"mass"},"mass":{"value":500,"unit":"mg"},"molar_mass":{"value":58.44,"unit":"g/mol"},"volume":{"value":50,"unit":"mL"}}	{"molarity":0.1711156742,"mass_concentration":10}
Known moles reference	{"basis":{"value":"moles"},"moles_input":{"value":0.5,"unit":"mol"},"volume":{"value":2,"unit":"L"}}	{"molarity":0.25}

Report an issue with this tool. Include the page URL, units, expected answer, and steps to reproduce. Do not include sensitive personal information.

On this page

Molarity formula

Molarity, more formally called amount concentration, is the amount of a constituent divided by the volume of the mixture. In common laboratory units:

c = n / V

where:

c is molarity in moles per liter, mol/L;
n is amount of solute in moles, mol;
V is final solution volume in liters, L.

When solute mass and molar mass are known:

n = m / M_r

Therefore:

c = m / (M_r × V)

Here m is solute mass in grams and M_r is the entered molar mass in grams per mole. The interface may use “molecular weight,” but molar mass is the dimensioned quantity used in the calculation.

Continue with How to Calculate Molarity to check the equation and unit sequence. To convert the calculated amount between moles and a count of molecules, atoms, ions, or formula units, use the Avogadro's Number Calculator.

How to use the calculator

Enter the mass of the solute and select its unit.
Enter the molar mass for the exact chemical form used, including waters of hydration where applicable.
Enter the final volume of the completed solution and select its unit.
Calculate the result.
Check the normalized grams, liters, and formula substitution before using the displayed value.

Do not enter the volume of solvent added at the beginning unless it is also the measured final solution volume. Dissolving a solute can change the total volume.

Continue with How to Prepare a Molar Solution to translate a target concentration into required mass.

Worked example using sodium chloride

Suppose 5.00 g of sodium chloride is brought to a final solution volume of 500.0 mL. PubChem lists a molecular weight of 58.44 g/mol for sodium chloride.

Convert the final volume:

500.0 mL = 0.5000 L

Calculate moles:

n = 5.00 g / 58.44 g/mol = 0.08556 mol

Calculate molarity:

c = 0.08556 mol / 0.5000 L = 0.1711 mol/L

With the significant figures supported by these inputs, report the result as approximately 0.171 M.

The corresponding mass concentration is:

5.00 g / 0.5000 L = 10.0 g/L

Molarity and mass concentration are different outputs. Molarity uses amount of substance per volume; mass concentration uses mass per volume.

How the calculator processes inputs

The calculator normalizes each input before calculation:

mass to grams;
molar mass to grams per mole;
final solution volume to liters.

It retains internal precision, calculates moles and molarity, and rounds only the displayed result. M, mM, micromolar, and nanomolar outputs are converted from the unrounded base result.

Mass concentration is a separate output equal to solute mass divided by final solution volume. It is not density and should not be interpreted as density.

Molarity units

Unit	Equivalent in mol/L	Symbol
molar	1	M
millimolar	10^-3	mM
micromolar	10^-6	µM
nanomolar	10^-9	nM
picomolar	10^-12	pM

For example, 0.00250 M = 2.50 mM = 2,500 µM.

Assumptions and limitations

The denominator is final solution volume, not solvent volume.
The molar mass must match the material used. An anhydrous compound and a hydrate have different molar masses.
Purity or assay is not applied unless the calculator has a separate, verified purity input.
The result is an analytical amount concentration for the entered chemical entity. It does not automatically calculate the concentrations of ions after dissociation.
Molarity is volume-based and can change when temperature changes solution volume.
Displayed decimals do not prove measurement accuracy. The balance, glassware, reagent, and inputs determine practical uncertainty.
The calculator does not determine solubility, reaction yield, pH, chemical activity, compatibility, or safe handling.

Common mistakes

Entering milliliters as liters without converting.
Using starting water volume instead of final solution volume.
Using the molar mass of the wrong hydrate, salt, or reagent form.
Confusing molarity with molality, mass percent, normality, or mass concentration.
Rounding moles before the final division.
Treating 0.1 M and 0.1 mM as equivalent; they differ by a factor of 1,000.

Inputs, outputs and result meaning

Inputs

Solve for: Choose a forward concentration calculation or a reverse preparation calculation. Available choices are Molarity from amount and volume and Required solute mass from target molarity.
Known solute amount: Choose whether the amount is known as mass or moles. Available choices are Mass and molar mass and Moles.
Amount of solute: Enter the amount of solute in moles or a supported submultiple. Supported units are moles (mol), millimoles (mmol), and micromoles (µmol).
Solute mass: Enter the mass of the exact solute form used. Supported units are grams (g), milligrams (mg), and kilograms (kg).
Molar mass: Use the molar mass for the exact chemical form, including hydration where applicable. Supported units are grams per mole (g/mol).
Target molarity: Enter the target amount concentration for the preparation. Supported units are moles per liter (mol/L), millimoles per liter (mmol/L), and micromoles per liter (umol/L).
Final solution volume: Enter completed solution volume, not starting solvent volume. Supported units are liters (L), milliliters (mL), and microliters (µL).

Outputs

Amount concentration: This is the primary result. It is displayed in mol/L. The display rule uses up to 4 decimal places. This result appears only in the applicable mode.
Required solute mass: This is the primary result. It is displayed in g. The display rule uses up to 6 decimal places. This result appears only in the applicable mode.
Amount of substance: It is displayed in mol. The display rule uses up to 5 decimal places.
Millimolar equivalent: It is displayed in mmol/L. The display rule uses up to 6 decimal places.
Micromolar equivalent: It is displayed in umol/L. The display rule uses up to 6 decimal places.
Mass concentration: It is displayed in g/L. The display rule uses up to 3 decimal places. This result appears only in the applicable mode.

c = m / (Mr × V). Keep the result label, unit, selected mode, and stated limitations together when sharing the answer.

Frequently asked questions

How do I calculate molarity from grams?

Divide solute mass in grams by molar mass in grams per mole to obtain moles. Divide those moles by final solution volume in liters. In one expression, c = m / (M_r × V).

Is molarity based on solution volume or solvent volume?

Molarity is based on the final volume of the solution. Adding solute to a measured volume of solvent does not necessarily leave the total volume unchanged.

What is the difference between M and mM?

1 M = 1,000 mM. A value of 0.025 M is therefore 25 mM.

Can molarity be negative?

A physical amount concentration is not negative. The interface should reject negative mass, molar mass, or volume values.

Does temperature affect molarity?

Molarity can change with temperature because it is defined using solution volume. Molality uses solvent mass and is not affected by thermal expansion in the same way.

Can this calculator prepare a safe laboratory solution?

It performs concentration arithmetic only. It does not evaluate hazards, incompatibilities, exothermic mixing, solubility, purity, equipment, or laboratory procedure. Follow the reagent's safety data and an approved protocol.