Molarity Calculator

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Example 1

A laboratory technician dissolved 10 g of sodium chloride (NaCl) in water and made the total volume up to 500 mL. The technician needs to report the molar concentration of this solution for the lab notebook.

Solution

The technician dissolved 10 g of NaCl in a total volume of 500 mL (0.500 L). First, calculate the moles of NaCl: n = 10 g / 58.44 g/mol = 0.1711 mol.

Applying the molarity formula, M = n / V = 0.1711 mol / 0.500 L = 0.3422 mol/L.

Answer

0.342 M (rounded to three significant figures)

Source: calculator.net Molarity Calculator

Example 2

A chemist needs exactly 0.50 mol of HCl for a neutralisation reaction. The stock bottle contains 2.0 M HCl. The chemist must calculate the volume to measure out.

Solution

The chemist needs 0.50 mol of HCl from a 2.0 M stock solution. Rearranging the molarity formula M = n / V gives V = n / M.

Substituting the values, V = 0.50 mol / 2.0 mol/L = 0.25 L, which is 250 mL.

Answer

250 mL of 2.0 M HCl. Measure 250 mL of the stock acid using a graduated cylinder.

Example 3

A biochemistry student needs to prepare 500 mL of 0.1 M NaCl for a protein purification protocol. The protocol specifies the concentration and volume precisely because the ionic strength of the buffer affects protein binding to the chromatography column.

Solution

The student needs 500 mL of 0.1 M NaCl. The molarity formula relates concentration, moles, and volume: M = m / (MW × V). Rearranging to solve for the mass of solute gives m = M × MW × V.

Substituting the values, m = 0.1 mol/L × 58.44 g/mol × 0.500 L = 2.922 g. The units cancel as mol/L × g/mol × L = g, confirming the result is in grams.

Answer

2.922 g of NaCl. Weigh 2.922 g of NaCl, dissolve in about 400 mL of distilled water in a beaker, transfer to a 500 mL volumetric flask, and fill to the mark.

Source: Adapted from LibreTexts CK-12 Foundation

Example 4

A laboratory requires 500 mL of 0.5 M HCl for a series of titrations. The stock solution is 6.0 M HCl. The technician must determine how much stock acid to dilute.

Solution

The technician needs 500 mL of 0.5 M HCl from a 6.0 M stock. The dilution formula C₁V₁ = C₂V₂ relates the stock and target concentrations and volumes.

Rearranging to solve for the stock volume needed: V₁ = (C₂ × V₂) / C₁ = (0.5 M × 0.500 L) / 6.0 M = 0.0417 L, which is 41.7 mL.

Answer

41.7 mL of 6.0 M HCl. Measure 41.7 mL of concentrated HCl, slowly add it to about 400 mL of distilled water, then dilute to 500 mL in a volumetric flask. Always add acid to water, never the reverse.

Source: calculator.net Molarity Calculator

By Dilawar Hussain (MS Chemistry)

Reviewed by Dr. Mian Sajawal Shah (PhD Research Fellow)

Published: 2026-04-07

Updated: 2026-06-09

References

[1]Pearson, Vogel's Textbook of Quantitative Chemical Analysis, 2000.
[2]IUPAC, IUPAC Gold Book - Molar Concentration. https://goldbook.iupac.org/terms/view/M03988

Glossary

Molarity (M) – The number of moles of solute per litre of solution, expressed in mol/L. It is the most widely used concentration unit in chemistry and is temperature-dependent because volume changes with temperature.
Mole (mol) – The SI base unit for amount of substance, defined as exactly 6.02214076 × 10²³ elementary entities (Avogadro’s number). One mole of any substance contains the same number of particles.
Molar mass (M) – The mass of one mole of a substance, expressed in grams per mole (g/mol). It is numerically equal to the molecular weight of the substance and is calculated by summing the atomic masses of all atoms in the chemical formula.
Solute – The component of a solution that is present in lesser amount and is dissolved by the solvent. In aqueous solutions, the solute is typically a solid, liquid, or gas that dissolves in water.
Solvent – The component of a solution that is present in greater amount and dissolves the solute. Water is the most common solvent in chemical laboratory work and is often called the universal solvent.
Solution – A homogeneous mixture of two or more substances consisting of a solute dissolved in a solvent. Solutions have uniform composition and properties throughout the mixture.
Avogadro’s number (N_A) – The number of particles in one mole of any substance, equal to 6.02214076 × 10²³. It provides the fundamental link between the macroscopic scale (grams) and the atomic scale (atoms or molecules).
Dilution – The process of reducing the concentration of a solution by adding more solvent without adding more solute. The relationship C₁V₁ = C₂V₂ governs dilution calculations.
Stock solution – A concentrated solution of known concentration that is stored and used to prepare more dilute working solutions as needed. Stock solutions save time and improve reproducibility in the laboratory.
Molality (m) – Moles of solute per kilogram of solvent, expressed in mol/kg. Unlike molarity, molality is temperature-independent because it depends on mass rather than volume. It is used in colligative property calculations and in situations where temperature fluctuates.

How to Use?

1
Select what you want to calculate
Choose from the dropdown: Molarity (M), Mass of solute (m), or Volume of solution (V). The other fields adjust automatically based on your selection.
2
Enter the known values
Type in the values you have. Use the unit dropdowns next to each field to switch between grams and milligrams, liters and milliliters, or molar and millimolar.
3
Use the chemical search (optional)
Search for any chemical compound by name, such as sodium chloride or glucose. The molar mass field fills in automatically using PubChem data, saving you a manual lookup.
4
Review and adjust units
Check that the units match your needs. The results panel shows the primary value plus alternative units like mM and uM so you always have the right format.
5
Click Calculate and interpret results
Press the Calculate button to see the answer instantly. The result includes the formula used and interactive graphs that visualize the relationship between variables.

Frequently Asked Questions

Use the standard formula M = (wt% × density × 1000) / molar mass. This formula converts weight-based concentration (grams of solute per 100 g solution) into moles per liter by using density to determine volume. Example (37% HCl): wt% = 37, density = 1.18 g/mL, molar mass = 36.46 g/mol. M = (37 × 1.18 × 1000) / 36.46 = 12.08 M. The calculator performs this conversion instantly and accurately.

Weight percent is mass-based while molarity is volume-based, so density is required for conversion. Formula: M = (wt% × density × 1000) / molar mass. Common conversions:
37% HCl → 12.08 M.
98% H₂SO₄ → 18.39 M.
50% NaOH → 19.06 M.
Glacial acetic acid → 17.45 M.

Use the Quick Fill feature for fast, pre-verified values.

Concentrated reagents show wt% purity and density on the label. Apply the formula M = (wt% × density × 1000) / molar mass using the exact values provided on your bottle. Standard reference values:
HCl 37% → 12.08 M.
H₂SO₄ 98% → 18.39 M.
HNO₃ 70% → 15.67 M.
NaOH 50% → 19.06 M.

Always prefer the values printed on your specific reagent bottle for highest accuracy.

The dilution formula C₁V₁ = C₂V₂ conserves the number of moles of solute. To find stock volume needed: V₁ = (C₂ × V₂) / C₁. Examples: 500 mL of 0.1 M HCl from 12.08 M stock → 4.14 mL stock. 1 L of 1 M H₂SO₄ from 18.39 M stock → 54.37 mL stock. The "Volume Needed" mode in this calculator applies the formula automatically.

Molarity (M) = moles of solute per liter of solution. Normality (N) = number of reactive equivalents per liter of solution. Relationship: N = M × n, where n is the equivalents factor. Common n values: HCl = 1, H₂SO₄ = 2, H₃PO₄ = 3, NaOH = 1. Normality is especially useful in titrations. Enable Advanced Mode to calculate both units simultaneously.

Determine stock molarity (use Quick Fill or the formula). Calculate required stock volume with C₁V₁ = C₂V₂. Add roughly half the final volume of distilled water to a volumetric flask. Slowly add the concentrated stock (acid to water only). Cool if necessary, then top up to the final volume and mix well. Label properly. This safe method is used for preparing 0.1 M, 1 M, and other common laboratory solutions.

Weight percent describes mass of solute per mass of solution, while molarity requires moles per volume (liter) of solution. Density bridges this gap by converting mass of solution into volume. Without density, accurate conversion is impossible. Even small variations in density can noticeably affect the calculated molarity.

Use the simple formula N = M × n, where n is the equivalents factor based on the number of reactive H⁺ or OH⁻ ions. Examples:
12.08 M HCl × 1 = 12.08 N.
18.39 M H₂SO₄ × 2 = 36.78 N.
19.06 M NaOH × 1 = 19.06 N.

This calculator computes normality automatically in Advanced Mode.

Dilution factor (DF) = initial concentration / final concentration = final volume / stock volume. Examples: 10-fold: 1 part stock + 9 parts diluent. 100-fold: 1 part stock + 99 parts diluent. For serial dilutions, multiply the individual factors. The calculator handles all dilution calculations instantly.

Calculate the required stock volume using V₁ = (C₂ × V₂) / C₁. Then follow safe lab practice: Start with half the final volume of water in the flask. Add the concentrated reagent slowly (acid to water). Cool if heat is generated. Make up to final volume and mix thoroughly. The calculator provides exact volumes for any target concentration.

Use the molar mass of the hydrated compound, not the anhydrous form. For CuSO₄·5H₂O, the molar mass is 249.69 g/mol (not 159.61 g/mol for anhydrous CuSO₄). The water of crystallization adds to the mass you weigh but does not change the moles of CuSO₄ in solution. Simply enter 249.69 as the molar mass in the calculator.

Molarity (M) is moles of solute per liter of solution. Molality (m) is moles of solute per kilogram of solvent. Molarity changes with temperature because volume expands. Molality is temperature-independent because mass does not change. Use molarity for most lab work, titrations, and spectrophotometry. Use molality for freezing point depression, boiling point elevation, and other colligative property calculations.

Always add concentrated acid to water slowly while stirring, never the reverse. Dilution of concentrated acids generates significant heat. Adding water to acid can cause rapid boiling and dangerous splashing. Wear safety goggles, a lab coat, and chemical-resistant gloves. Work in a fume hood for volatile acids like HCl and HNO₃. Use this calculator to determine the exact volumes needed before you start.

For two solutions of the same solute mixed together, calculate total moles and divide by total volume. Total moles = (M₁ × V₁) + (M₂ × V₂). Total volume = V₁ + V₂ assuming volumes are additive. Mixture molarity = total moles / total volume. For different solutes, calculate each concentration independently.

Standard reference values:
Hydrochloric acid (37% wt) = 12.08 M.
Sulfuric acid (98%) = 18.39 M.
Nitric acid (70%) = 15.67 M.
Phosphoric acid (85%) = 14.63 M.
Glacial acetic acid (99.7%) = 17.45 M.
Ammonium hydroxide (28%) = 14.53 M.
Sodium hydroxide (50%) = 19.06 M.

Always verify the exact wt% and density printed on your specific reagent bottle, as values vary slightly between manufacturers.

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Glossary

Molarity (M) – The number of moles of solute per litre of solution, expressed in mol/L. It is the most widely used concentration unit in chemistry and is temperature-dependent because volume changes with temperature.

Mole (mol) – The SI base unit for amount of substance, defined as exactly 6.02214076 × 10²³ elementary entities (Avogadro’s number). One mole of any substance contains the same number of particles.

Molar mass (M) – The mass of one mole of a substance, expressed in grams per mole (g/mol). It is numerically equal to the molecular weight of the substance and is calculated by summing the atomic masses of all atoms in the chemical formula.

Solute – The component of a solution that is present in lesser amount and is dissolved by the solvent. In aqueous solutions, the solute is typically a solid, liquid, or gas that dissolves in water.

Solvent – The component of a solution that is present in greater amount and dissolves the solute. Water is the most common solvent in chemical laboratory work and is often called the universal solvent.

Solution – A homogeneous mixture of two or more substances consisting of a solute dissolved in a solvent. Solutions have uniform composition and properties throughout the mixture.

Avogadro’s number (N_A) – The number of particles in one mole of any substance, equal to 6.02214076 × 10²³. It provides the fundamental link between the macroscopic scale (grams) and the atomic scale (atoms or molecules).

Dilution – The process of reducing the concentration of a solution by adding more solvent without adding more solute. The relationship C₁V₁ = C₂V₂ governs dilution calculations.

Stock solution – A concentrated solution of known concentration that is stored and used to prepare more dilute working solutions as needed. Stock solutions save time and improve reproducibility in the laboratory.

Molality (m) – Moles of solute per kilogram of solvent, expressed in mol/kg. Unlike molarity, molality is temperature-independent because it depends on mass rather than volume. It is used in colligative property calculations and in situations where temperature fluctuates.

How to Use?

Select what you want to calculate

Choose from the dropdown: Molarity (M), Mass of solute (m), or Volume of solution (V). The other fields adjust automatically based on your selection.

Enter the known values

Type in the values you have. Use the unit dropdowns next to each field to switch between grams and milligrams, liters and milliliters, or molar and millimolar.

Use the chemical search (optional)

Search for any chemical compound by name, such as sodium chloride or glucose. The molar mass field fills in automatically using PubChem data, saving you a manual lookup.

Review and adjust units

Check that the units match your needs. The results panel shows the primary value plus alternative units like mM and uM so you always have the right format.

Click Calculate and interpret results

Press the Calculate button to see the answer instantly. The result includes the formula used and interactive graphs that visualize the relationship between variables.