Molarity Calculator
This molarity calculator converts mass concentration of any solution to molar concentration (M), and recalculates grams per milliliter (g/mL) to moles. The molarity calculator computes any missing value — mass, molecular weight, volume, concentration, or molarity — when 3 of the 5 values are known.
The molarity definition, the molarity formula, and practical examples of molar solutions are explained in the sections below. The mole definition, molarity units, and a direct comparison of the molarity formula vs molality formula are also covered. A step-by-step tutorial on how to calculate molarity of a concentrated solution and a guide to finding molar concentration by titration are included at the end.
Molarity Calculate
Formula Used
Enter 3 values above to see the step-by-step solution
How to use the molarity calculator
The molarity calculator accepts 5 variables. Enter any 3 known values and the calculator determines the remaining values automatically.
- Enter the concentration of the solution into the 4th field. The mass concentration is equal to the density for a pure substance. The default unit is g/mL (grams per milliliter). Change the unit from the dropdown before entering the value.
- Enter the molecular weight (molar mass) of the substance. The default unit is grams per mole (g/mol). Other unit options include kg/mol, kg/kmol, and lb/lbmol.
- The calculator computes the molarity instantly. The default unit is molars (M). Change the unit to mM, µM, nM, pM, fM, or aM from the dropdown.
- Leave the mass concentration empty, if the mass concentration is unknown. Enter the mass of the substance in grams (or change the unit to mg, kg, oz, lb, or other options) and enter the volume of the solution in liters (or mL, µL, gallons).
- The calculator determines the mass concentration and molarity from the mass and volume values provided.
Example: Sulphuric acid (H₂SO₄) has a molar mass of 98 g/mol and a mass concentration of 10 g/mL. Entering these 2 values into the calculator with a volume gives a molarity of 102.0408 M.
A second example: 970 g of H₂SO₄ in a 2.1 L solution. The molarity calculator returns a molarity of 4.71331 M and a mass concentration of 0.461905 g/mL.
Molar concentration – an introduction
Most materials in everyday life are not pure. They are mixtures. Mixtures consist of a collection of different compounds. Orange juice, tea, detergents, and milk are all mixtures. Mixtures are not limited to liquids — solids and gases can be mixtures as well.
There are 2 types of mixtures in chemistry:
Components are uniformly distributed throughout the mixture, and there is only one phase of matter observed. Homogeneous mixtures are also known as solutions and may occur in the solid, liquid, or gaseous state. Separating the mixture components by simple methods is not possible, but no chemical change has occurred to any of the components.
Components of the mixture are not uniformly distributed and may have regions with different properties. Different samples of the mixture are not identical. At least two phases are always present in the mixture, and separating them physically is possible.
Concentration is the most important parameter for any substance involved in a chemical reaction. Concentration measures how much of a substance is dissolved in a given volume of solution.
Chemists use many different units for describing concentration. Molarity, also known as molar concentration, is the most common way of expressing concentration. When reactants (compounds) are expressed in mole units, writing chemical reactions with integer coefficients becomes straightforward. First, the definition of the mole is established below, so molarity can be properly defined after.
Mole definition
The mole (mol) is the SI unit of measurement for the amount of substance. The definition was adopted in 1971 and is based on carbon-12:
"The mole is the amount of substance of a system which contains as many elementary entities as there are atoms in 0.012 kilograms of carbon-12. When the mole is used, the elementary entities must be specified and may be atoms, molecules, ions, electrons, other particles, or specified groups of such particles."
The molar mass of carbon-12 is exactly 12 grams per mole: M(¹²C) = 12 g/mol. The word "substance" in the definition should be replaced with the specific substance name, such as the amount of hydrogen chloride (HCl) or the amount of carbon dioxide (CO₂). Specifying the empirical chemical formula of the compound is required.
The newest convention, effective as of 20th May 2019, defines the mole as the amount of a chemical substance that contains exactly 6.02214076 × 10²³ particles (atoms, molecules, ions). That number is known as Avogadro's constant, and its symbol is NA or L.
1 mole of N₂ weighs 28 g. 1 mole of NaCl weighs 58.5 g. Moles allow reading weight directly from the periodic table.
The number of entities X in a sample — N(X) — links to the moles of X in that sample — n(X) — with the relation: n(X) = N(X) / NA. N(X) is dimensionless, and n(X) has the SI unit mole.
What is molarity?
Molarity expresses the concentration of a solution. Molarity is the number of moles of a substance (solute) dissolved per liter of solution (not per liter of solvent).
Molarity means exactly the same as molar concentration (M).
Molarity formula
The molarity formula calculates the molar concentration of a solution:
Concentration refers to the mass concentration of the solution, expressed in density units (g/L or g/mL). Molar mass is the mass of 1 mole of the solute, expressed in grams per mole (g/mol). Molar mass is a constant property — the molar mass of water is 18 g/mol.
The calculator also finds the mass of substance needed to reach a target molar concentration:
Where mass is the mass of solute in grams, and volume is the total volume of solution in liters.
Try the molarity formula
Enter values below to see the molarity formula in action. The calculator supports 2 modes: calculating from concentration (g/mL) and from mass + volume.
Molarity units
The units of molar concentration are moles per cubic decimeter, written as mol/dm³ or M (pronounced "molar"). 1 cubic decimeter equals 1 liter, so mol/dm³ and mol/L are numerically identical.
The molar concentration of a solute is sometimes written with square brackets around the chemical formula. For example, the concentration of hydroxide anions is written as [OH⁻].
Older references use moles per liter (mol/L) notation. Modern conventions favor the M notation. This calculator supports 7 molarity units: M, mM, µM, nM, pM, fM, and aM.
Molarity (uppercase M) should not be confused with molality (lowercase m). The difference between these 2 terms is explained in the next section.
How to calculate molarity
To calculate the molarity of a solution, follow these 6 steps:
- Choose the substance. This example uses hydrochloric acid (HCl).
- Find the molar mass of the substance. The molar mass of HCl is 36.46 g/mol.
- Determine the mass concentration. This example uses 5 g of HCl in a 1.2 liter solution.
- Convert: mass / volume = molarity × molar mass → mass / (volume × molar mass) = molarity.
- Substitute: molarity = 5 ÷ (1.2 × 36.46) = 0.114 mol/L = 0.114 M.
- Use the molarity calculator above to verify the result. Enter mass, volume, and molecular weight to get the molarity instantly.
Molarity vs. molality
Both molarity and molality express solution concentration, but there is 1 significant difference. Molarity measures the amount of substance per unit volume of solution. Molality measures the amount of substance per unit mass of the solvent. Molality is the number of moles of solute per kilogram (kg) of solvent.
Converting between molarity and molality uses this formula:
| Property | Molarity | Molality |
|---|---|---|
| Definition | Moles of solute ÷ liters of solution | Moles of solute ÷ kilograms of solvent |
| Symbol | M | m or b |
| Unit | mol/L | mol/kg |
| Temperature & Pressure | Dependent | Independent |
| Usage | More popular, practical in the lab, faster | Accurate but rarely used |
Molar solution — life examples
Mixtures and solutions are a permanent part of the environment. The table below shows the orders of magnitude for molar concentration, with examples from nature and the human body. Click any row to see more details.
| Molarity | SI Prefix | Value | Example |
|---|---|---|---|
10⁻¹⁵ | fM | 2 fM | Bacteria in surface seawater (1×10⁹/L) |
10⁻¹⁴ | — | 50–100 fM | Gold in seawater |
10⁻¹² | pM | 7.51–9.80 pM | Erythrocytes in blood (adult male) |
10⁻⁷ | — | 101 nM | H₃O⁺ and OH⁻ ions in pure water at 25 °C |
10⁻⁴ | — | 180–480 µM | Uric acid in blood |
10⁻³ | mM | 7.8 mM | Upper bound for healthy blood glucose (2h post-meal) |
10⁻² | cM | 44.6 mM | Pure ideal gas at 0 °C and 101.325 kPa |
10⁻¹ | dM | 140 mM | Sodium ions in blood plasma |
10² | hM | 118.8 M | Pure osmium at 20 °C (22.587 g/cm³) |
10⁴ | myM | 24 kM | Helium in solar core (150 g/cm³ × 65%) |
Determining the molar concentration by titration
Titration is a technique for finding the concentration of an unknown solution, based on the chemical reaction with a solution of known concentration. The process works by adding the titrant (known concentration and volume) to a known quantity of the unknown solution (the analyte) until the reaction reaches completion. The concentration of the analyte is determined by measuring the volume of titrant used.
There are 3 steps to find molarity using titration:
- Prepare the concentrations — place the analyte in an Erlenmeyer flask and the titrant in a burette.
- Mix the concentrations — add the titrant to the analyte until the endpoint is reached. Use an acid-base indicator (phenolphthalein shows a color change from pink to colorless).
- Calculate the molarity — use the titration formula. For a 1:1 titrant-to-analyte ratio: acid molarity × acid volume = base molarity × base volume. Modify the formula for ratios other than 1:1.
Example: 35 mL of 1.25 M HCl acid titrates a 25 mL NaOH solution. 1 mole of HCl reacts with 1 mole of NaOH (1:1 ratio). Acid molarity × acid volume = 1.25 × 35 = 43.75. Base molarity = 43.75 ÷ 25 = 1.75 M.
Try the titration calculator
Titration Calculator
Use the 1:1 ratio formula: acid molarity × acid volume = base molarity × base volume
Invention of the molarity calculator
This molarity calculator was built to make molarity calculations fast and accessible. Molarity calculations involve unit conversions and multi-step arithmetic that are tedious to perform manually. The calculator handles all conversions — from micrograms to kilograms, milliliters to gallons, and molars to attomolars — in a single step.
The calculator serves 3 main audiences: students learning solution chemistry, researchers preparing molar solutions in the laboratory, and professionals in the food and pharmaceutical industries who require precise concentration measurements for quality control and regulatory compliance.
The tool supports over 30 unit combinations across 5 variables (mass, molecular weight, volume, concentration, molarity). Each calculation includes a step-by-step formula breakdown, calculation history, and one-click copy and share functions.
FAQs
How do I calculate pH from molarity?
Calculate the concentration of the acid or alkaline component of the solution first. For acidic solutions, find -log[H⁺] to get the pH. For alkaline solutions, find -log[OH⁻] and subtract the result from 14. For example, a 0.01 M HCl solution has [H⁺] = 0.01, so pH = -log(0.01) = 2.
How do you make a molar solution?
Find the molecular weight of the substance in g/mol. Multiply the molecular weight by the number of moles needed (1 mole for a 1 M solution). Weigh out the calculated mass in grams and place it in a volumetric flask. Add 1 liter (1000 mL) of solvent to the flask. The result is a 1 M molar solution.
What is molar volume?
Molar volume is the volume that 1 mole of a substance occupies at a specific temperature and pressure. Molar volume is calculated by dividing the molar mass by the substance's density at that temperature and pressure. At standard temperature and pressure (STP), the molar volume of an ideal gas is 22.4 L/mol.
How do I find moles from molarity?
Multiply the molarity (M) by the volume (L) of the solution. The formula is: moles = molarity × volume. For example, 0.5 M NaCl in 2 L contains 0.5 × 2 = 1.0 mole of NaCl.
Is molarity the same as concentration?
No, molarity is not the same as concentration. Concentration is a broad measure of how many moles of a substance are dissolved in a given amount of liquid, and can have any volume units. Molarity is a specific type of concentration measured in moles per liter (mol/L) of solution.
What is the molarity of water?
Water has a molarity of 55.5 M. 1 liter of water weighs 1000 g (0.997 kg/L). The molar mass of water is 18.02 g/mol. Dividing 1000 g by 18.02 g/mol gives 55.5 mol/L, which equals 55.5 M.
Why do we use molarity?
Molarity provides a standard metric for comparing solution concentrations without unit conversions. Concentration units range from nanograms per milliliter (ng/mL) to tons per gallon (t/gal). Molarity (M), measured in moles per liter, offers a single, consistent unit for quick comparison across all chemical solutions.