Use this Molarity Calculator to calculate moles, mass concentration, and molarity from solute mass, molar mass, and solution volume. Enter the mass of solute, its molar mass, and the final solution volume to find the number of moles and the molar concentration in mol/L.

Important Note: This Molarity Calculator provides educational chemistry calculations from solute mass, molar mass, and final solution volume. It calculates moles, mass concentration, and molarity using standard concentration formulas.

Molarity is based on the final volume of the solution, not simply the amount of solvent added. For accurate lab preparation, the volume should represent the final solution volume after the solute is dissolved and the solution is made up to the target volume.

This calculator does not identify unknown chemicals, calculate molar mass from a formula, account for temperature, density, nonideal solution behavior, activity coefficients, purity, hydrates, or lab measurement uncertainty. Follow your lab protocol, chemical safety guidance, and instructor or professional instructions when preparing real solutions.

Reviewed by: AjaxCalculators Editorial Team
Last updated: April 29, 2026
Method source: Standard chemistry concentration formulas using n = m / M_r, c = m / V, and M = n / V
Editorial standards: AjaxCalculators Editorial Policy

What This Molarity Calculator Calculates

This calculator finds the molarity of a solution from solute mass, molar mass, and solution volume. It also calculates the number of moles and the mass concentration of the solute.

The calculator can calculate:

• Moles of solute
• Mass concentration
• Molarity
• Molar concentration in mol/L
• Step-by-step derivation

The live tool uses three main inputs: mass, molar mass, and volume. It then reports moles, mass concentration, and molarity.

What Molarity Means

Molarity, written as M, is the number of moles of solute per liter of solution.

Molarity = moles of solute ÷ liters of solution

Using symbols:

M = n / V

In this formula:

• M is molarity in mol/L
• n is moles of solute
• V is solution volume in liters

For example, a solution containing 1 mole of solute in 1 liter of final solution has a molarity of 1 M.

Important: Use Final Solution Volume

Molarity uses liters of solution, not just liters of solvent. This means the volume should represent the final prepared solution volume whenever accuracy matters.

For example, if a lab procedure says to dissolve a solute and dilute to a final volume of 1.000 L, the volume used in the molarity formula is 1.000 L. It is not necessarily the amount of water added before the solute dissolved.

How the Molarity Calculator Works

1) Convert Mass to Moles

The calculator first converts solute mass into moles using molar mass.

Moles = mass ÷ molar mass

Using symbols:

n = m / M_r

In this formula:

• n is moles of solute
• m is solute mass in grams
• M_r is molar mass in g/mol

2) Calculate Mass Concentration

The calculator also finds mass concentration by dividing mass by volume.

Mass concentration = mass ÷ volume

Using symbols:

c = m / V

If mass is entered in grams and volume is entered in liters, the mass concentration is in g/L.

3) Calculate Molarity

After moles are known, molarity is calculated by dividing moles by solution volume.

Molarity = moles ÷ volume

Using symbols:

M = n / V

Because n = m / M_r, the combined formula is:

M = m / (M_r × V)

Molarity Formula Summary

What You Want to Find	Formula	Meaning
Moles from mass	n = m / Mr	Solute mass divided by molar mass
Mass concentration	c = m / V	Solute mass divided by solution volume
Molarity from moles	M = n / V	Moles of solute divided by liters of solution
Molarity from mass, molar mass, and volume	M = m / (Mr × V)	Direct formula when mass, molar mass, and volume are known
Mass from target molarity	m = M × Mr × V	Useful when preparing a target molar solution
Volume from mass and molarity	V = m / (M × Mr)	Useful when solving for required solution volume

Worked Example: Calculate Molarity from Mass

Suppose you dissolve 58.44 g of sodium chloride in enough water to make 1 L of solution. The molar mass of sodium chloride is 58.44 g/mol.

Step 1: Calculate moles
n = m / M_r
n = 58.44 / 58.44
n = 1 mol

Step 2: Calculate molarity
M = n / V
M = 1 / 1
M = 1 M

So, 58.44 g of NaCl in 1 L of final solution gives a molarity of 1 M.

Worked Example: Calculate Moles and Molarity

Suppose a solution is prepared using:

• Mass: 10 g
• Molar mass: 50 g/mol
• Volume: 2 L

Step 1: Calculate moles
n = mass ÷ molar mass
n = 10 ÷ 50
n = 0.2 mol

Step 2: Calculate molarity
M = moles ÷ volume
M = 0.2 ÷ 2
M = 0.1 M

Step 3: Calculate mass concentration
c = mass ÷ volume
c = 10 ÷ 2
c = 5 g/L

So, the solution contains 0.2 mol of solute, has a mass concentration of 5 g/L, and has a molarity of 0.1 M.

Worked Example: Calculate Molarity of Glucose Solution

Suppose you dissolve 18.0 g of glucose in enough water to make 0.500 L of solution. The molar mass of glucose is about 180.16 g/mol.

Step 1: Convert mass to moles
n = 18.0 ÷ 180.16
n ≈ 0.0999 mol

Step 2: Divide by solution volume
M = 0.0999 ÷ 0.500
M ≈ 0.200 M

So, 18.0 g of glucose in 0.500 L of solution is approximately 0.200 M.

Worked Example: Calculate Mass Concentration

Suppose a solution contains 25 g of solute in 0.500 L of solution.

Step 1: Use the mass concentration formula
c = m / V

Step 2: Substitute the values
c = 25 / 0.500

Step 3: Calculate
c = 50 g/L

So, the mass concentration is 50 g/L.

Worked Example: Find Mass Needed for a Target Molarity

The live calculator focuses on finding molarity from mass, molar mass, and volume, but the same formula can be rearranged. Suppose you want to prepare 0.250 L of a 0.100 M solution using a solute with molar mass 58.44 g/mol.

Step 1: Use the rearranged formula
m = M × M_r × V

Step 2: Substitute the values
m = 0.100 × 58.44 × 0.250

Step 3: Calculate
m = 1.461 g

So, you would need about 1.46 g of solute to prepare 0.250 L of a 0.100 M solution, assuming the final solution volume is made up to 0.250 L.

How to Use This Molarity Calculator

1. Enter the mass of solute in grams.
2. Enter the molar mass of the solute in g/mol.
3. Enter the volume of the final solution in liters.
4. Click Calculate.
5. Review the calculated moles, mass concentration, and molarity.
6. Use the step-by-step section to check the formula path.
7. Click Reset to clear the calculator and start again.

How to Interpret the Results

Result	What It Means	Important Caution
Moles	The amount of solute in mol, calculated from mass and molar mass.	Only accurate if the entered molar mass matches the exact substance used.
Mass concentration	The amount of solute mass per liter of solution.	If mass is in grams and volume is in liters, the result is in g/L.
Molarity	The number of moles of solute per liter of final solution.	Use final solution volume, not just the amount of solvent added.
Step-by-step derivation	The formula path used to calculate moles, mass concentration, and molarity.	Check mass, molar mass, volume, and units before using the result in lab work.

Moles, Molar Mass, and Molarity Explained

Quantity	Symbol	Common Unit	Meaning
Mass	m	g	Amount of solute by mass
Molar mass	Mr	g/mol	Mass of one mole of the substance
Moles	n	mol	Amount of substance
Volume	V	L	Final solution volume
Molarity	M	mol/L	Moles of solute per liter of final solution

Mass Concentration vs Molarity

Mass concentration and molarity both describe solution concentration, but they use different bases.

Concentration Type	Formula	Common Unit	Depends on Molar Mass?
Mass concentration	c = m / V	g/L	No
Molarity	M = n / V	mol/L or M	Yes

Two solutions can have the same mass concentration but different molarity if the solutes have different molar masses. Molarity depends on how many moles of solute are present, not only how many grams are present.

Why Molar Mass Matters

Molar mass converts grams into moles. Because molarity is based on moles, the same mass can produce different molarities depending on the substance.

For example, 10 g of a substance with molar mass 50 g/mol gives:

10 ÷ 50 = 0.2 mol

But 10 g of a substance with molar mass 200 g/mol gives:

10 ÷ 200 = 0.05 mol

If both are dissolved to the same final volume, the first solution has a higher molarity because it contains more moles of solute.

Common Molarity Unit Conversions

Unit	Meaning	Relationship to M
M	Molar	1 M = 1 mol/L
mM	Millimolar	1 mM = 0.001 M
μM	Micromolar	1 μM = 0.000001 M
nM	Nanomolar	1 nM = 0.000000001 M
mol/L	Moles per liter	Same as M

Common Volume Unit Conversions

Volume Unit	Equivalent in Liters
1 mL	0.001 L
100 mL	0.100 L
250 mL	0.250 L
500 mL	0.500 L
1000 mL	1 L

If your solution volume is measured in milliliters, convert it to liters before using the molarity formula manually.

Common Molarity Examples

Mass	Molar Mass	Volume	Moles	Molarity
58.44 g	58.44 g/mol	1 L	1 mol	1 M
29.22 g	58.44 g/mol	1 L	0.5 mol	0.5 M
5.844 g	58.44 g/mol	1 L	0.1 mol	0.1 M
5.844 g	58.44 g/mol	0.5 L	0.1 mol	0.2 M
10 g	50 g/mol	2 L	0.2 mol	0.1 M

How to Find Molar Mass

Molar mass is usually found from the chemical formula. Add the atomic masses of all atoms in the formula.

For example, sodium chloride is NaCl:

• Na is about 22.99 g/mol
• Cl is about 35.45 g/mol

So:

Molar mass of NaCl ≈ 22.99 + 35.45 = 58.44 g/mol

For hydrates, ions, acids, and complex formulas, make sure the molar mass matches the exact substance used in the solution.

Preparing Solutions and Molarity

When preparing a molar solution in a lab, the usual workflow is:

1. Calculate the required mass of solute.
2. Weigh the solute accurately.
3. Dissolve the solute in some solvent.
4. Transfer to a volumetric flask or final container.
5. Dilute to the final target solution volume.
6. Mix thoroughly.

The final solution volume is the volume used in the molarity calculation. Adding solute to exactly 1 L of water may not produce exactly 1 L of final solution.

When to Use This Molarity Calculator

This calculator is useful when you know the solute mass, molar mass, and solution volume.

Common uses include:

• chemistry homework
• general chemistry solution problems
• lab report concentration checks
• preparing solution concentration examples
• converting grams of solute into moles
• calculating mol/L from mass and volume
• checking mass concentration in g/L
• learning the relationship between mass, moles, volume, and molarity

Common Mistakes to Avoid

• Do not use milliliters directly in the molarity formula unless you convert them to liters or use a consistent mmol/mL method.
• Do not confuse mass concentration in g/L with molarity in mol/L.
• Do not use the wrong molar mass for the solute.
• Do not use solvent volume when the problem gives final solution volume.
• Do not forget that molarity depends on volume, so dilution changes molarity.
• Do not use molarity for gas ppm, mass percent, or molality unless the units have been properly converted.
• Do not round molar mass too aggressively if the calculation requires precision.
• Do not assume density is irrelevant when converting from mass percent or volume percent to molarity.

Important Assumptions and Limitations

• This calculator assumes mass is entered in grams.
• It assumes molar mass is entered in g/mol.
• It assumes volume is entered in liters.
• The volume should represent final solution volume for accurate molarity.
• It calculates moles, mass concentration, and molarity from the values entered by the user.
• It does not calculate molar mass from a chemical formula.
• It does not verify whether the selected molar mass matches the exact compound, hydrate, ion, acid, salt, or reagent form.
• It does not account for purity percentage, assay value, water of hydration, density, temperature expansion, nonideal mixing, activity coefficients, or volume change on dissolving.
• It does not calculate dilution, pH, molality, normality, ppm, mass percent, or solution stoichiometry.
• It does not replace a lab protocol, safety data sheet, instructor guidance, analytical method, or chemical safety procedure.
• Displayed values may be rounded for readability.

Practical Uses

This Molarity Calculator can be useful for:

• calculating solution molarity from solute mass
• checking moles from grams
• finding mass concentration in g/L
• preparing chemistry solution examples
• checking lab-report calculations
• converting mass and molar mass into mol/L
• understanding concentration units
• building the first step before dilution, pH, or stoichiometry calculations

When You May Need a Different Calculator

This calculator is best for finding molarity from mass, molar mass, and final solution volume. You may need another calculator if your problem uses a different concentration method.

Need	Better Tool or Method
Calculate dilution	Use M1V1 = M2V2
Convert ppm or ppb to molarity	Use a PPM to Molarity Calculator with molar mass assumptions
Calculate pH	Use acid/base concentration and pH formulas
Find molar mass from a formula	Use a molar mass or formula mass calculator
Calculate molality	Use moles of solute per kilogram of solvent
Convert mass percent to molarity	Use solution density and mass percent data
Perform solution stoichiometry	Use a balanced chemical equation and stoichiometric ratios

References

1. OpenStax Chemistry 2e — Molarity
2. OpenStax Chemistry 2e — Chapter 3 Summary
3. Chemistry LibreTexts — Concentration of Solutions
4. Sigma-Aldrich — Mass Molarity Calculator
5. Tocris — Molarity Calculator

Related Calculators

• PPM to Molarity Calculator
• pH Calculator
• Dilution Ratio Calculator
• Theoretical Yield Calculator
• Percent Yield Calculator
• mg to mL Calculator
• mL to Grams Converter
• Avogadro’s Number Calculator

Chemistry Disclaimer

This Molarity Calculator provides educational molarity calculations from solute mass, molar mass, and final solution volume. It assumes grams, g/mol, liters, and standard concentration formulas. Results depend on accurate measurements, correct molar mass, correct final solution volume, and appropriate rounding.

This calculator does not calculate molar mass from formulas, verify chemical identity, account for purity, hydrates, density, temperature effects, nonideal solution behavior, volume change on dissolving, activity coefficients, or laboratory measurement uncertainty. It does not replace a lab protocol, safety data sheet, chemical handling procedure, instructor instruction, or professional analytical method.