Molarity Calculator
Enter moles and volume to calculate the molarity of a solution.
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Result
Press Calculate to see the result.
Molarity Calculator is an essential tool for chemistry labs to accurately calculate the molarity of a solution. Molarity expresses the number of moles of solute dissolved in one liter (L) of solution, and is the most widely used unit for understanding quantitative relationships in chemical reactions.
Molarity (M) is the most fundamental concentration unit in chemistry, representing the amount of solute relative to the solution volume. Its unit is moles per liter (mol/L) or M(molar) (molar), and is indispensable for stoichiometric calculations, reagent preparation, solution dilution, and many other laboratory activities.
This calculator computes molarity in two ways: by directly entering moles and volume, or indirectly via the solute mass and molar mass. It is useful across many fields that require accurate concentration calculations when preparing reagents or designing chemical reactions.
Molarity calculations are used in a wide range of fields such as the pharmaceutical industry, food science, environmental analysis, and clinical research. It serves as an educational tool that helps students grasp fundamental chemistry concepts and as a practical tool that helps researchers obtain accurate experimental data.
Term Glossary
- Molarity (M)
- A concentration unit expressed as the number of moles (mol) of solute dissolved in one liter (L) of solution, denoted as mol/L or M.
- Molar mass
- The mass of one mole of a substance, equal to the sum of the atomic weights of its constituent elements, with unit g/mol. Used to convert solute mass into moles.
- Enter moles of solute → Enter the moles of solute (mol).
- Enter volume → Enter the solution volume in liters (L).
- Calculate → Click the Calculate button.
- View result → Check the molarity in mol/L or M.
0.5 mol solute in 1 L solution
M = 0.5mol ÷ 1L = 0.5M
2 mol solute in 500 mL (0.5 L) solution
M = 2mol ÷ 0.5L = 4M
NaCl 58.44g (1mol), 1L
M = 1mol ÷ 1L = 1M
Basic Molarity Formula
Molarity is calculated by dividing the moles of solute by the solution volume.
- M is the molarity, with unit mol/L (M).
- n is the number of moles of solute, with unit mol.
- V is the solution volume, with unit liter (L).
Mass-Based Formula
Calculate moles from the solute mass and molar mass, then compute molarity.
- m is the solute mass, with unit gram (g).
- MW is the molar mass (molecular weight), with unit g/mol.
- V is the solution volume, with unit liter (L).
Example
For example, if 58.44 g of NaCl (table salt) is dissolved in water to make 1 L of solution?
Therefore the molarity of this solution is 1 M (1 molar), meaning 1 mole of NaCl is dissolved per liter.
Concentration Unit Conversion
Molarity can be converted into various concentration units.
- Molarity (M): mol/L - most commonly used in chemistry
- Mass concentration: g/L - mass-based concentration
- Molality: mol/kg - solvent-based concentration (useful for high-temp/high-pressure experiments)
- Volume fraction: mL/L - volume-based concentration
- Percentage: % - ratio relative to the whole
Using the Dilution Formula
Use the M₁V₁ = M₂V₂ formula when changing concentration.
- Dilution: dilute the stock to prepare a solution of the desired concentration
- Concentration: raise concentration by evaporating the solvent
- Mixing: mix solutions of different concentrations
⚠️ Caution
For molarity, the solution volume is based on the final volume after the solute is dissolved. Dissolving solute in solvent can change the volume, so you must measure and use the final volume.
Real-Life Applications
- Pharmaceuticals: precisely control drug concentration for manufacturing
- Food industry: adjust concentrations of additives, preservatives, spices, etc.
- Environmental science: measure water pollution, analyze air pollutants
- Clinical research: analysis of biological samples such as blood and urine
Lab Tips
- Precise weighing: use an analytical balance for accurate mass measurement
- Complete dissolution: stir thoroughly until the solute is fully dissolved
- Check temperature: note that volume can vary with temperature
- Safety gear: wear goggles, gloves, and other safety gear during experiments
QWhat is molarity?
Molarity is a concentration unit expressed as the number of moles of solute dissolved in one liter of solution, denoted mol/L or M. It is the most widely used unit for quantitative relationships in chemistry.
QWhat is the difference between a mole and molarity?
A mole is a unit of amount of substance (about 6.022 × 10²³ particles), while molarity is the concentration obtained by dividing moles of solute by the solution volume in liters. A mole measures quantity; molarity measures concentration.
QHow do I convert grams to moles?
Divide the mass in grams by the molar mass in g/mol to get the number of moles. For example, 58.44 g of NaCl divided by its molar mass of 58.44 g/mol equals 1 mole.
QWhy must volume be in liters?
Since molarity is defined as moles per liter of solution, using other units such as mL or cm³ changes the result. Divide mL by 1000 to convert to liters for an accurate molarity.
QHow does dilution affect molarity?
Adding solvent increases the volume while the moles of solute stay the same, so the molarity decreases. The relationship before and after dilution is given by M₁V₁ = M₂V₂.