Molarity Calculator
Find the grams of solute, molarity or volume of a solution, solve C1V1 = C2V2 dilutions and get molar mass from a formula, with lab preparation steps.
Element symbols need capitals. Brackets and hydrates work: Ca(OH)2, Al2(SO4)3, CuSO4·5H2O (type * or . for the dot).
Dissolve 7.305 g of NaCl and fill to 250 mL with water to make a 0.5 M solution.
How to prepare it
Standard method for a solution of known molarity.
- Weigh 7.305 g of NaCl on a balance and record the actual mass.
- Dissolve it in about 200 mL of water in a beaker, less than the final volume.
- Transfer it to a 250 mL volumetric flask, rinsing the beaker into it two or three times.
- Add water until the bottom of the meniscus sits on the 250 mL mark.
- Stopper and invert about 20 times to mix. The solution is 0.5 M.
Your calculation
The same steps the calculator runs, with your numbers.
- Volume: 250 mL ÷ 1,000 = 0.25 L.
- Moles: n = c × V = 0.5 mol/L × 0.25 L = 0.125 mol.
- Mass: m = n × M = 0.125 mol × 58.44 g/mol = 7.305 g.
- Mass concentration: 7.305 g ÷ 0.25 L = 29.22 g/L, and 29.22 ÷ 10 = 2.922 g per 100 mL.
- Particles: 0.125 mol × 6.02214076 × 10²³ per mol = 7.528 × 10²².
Mass at other molarities
Same final volume (250 mL of NaCl solution) with a different target concentration.
| Molarity | Mass of NaCl | Moles |
|---|---|---|
| 1 mM | 14.61 mg | 2.5 × 10⁻⁴ mol |
| 10 mM | 146.1 mg | 0.0025 mol |
| 50 mM | 730.5 mg | 0.0125 mol |
| 0.1 M | 1.461 g | 0.025 mol |
| 0.25 M | 3.652 g | 0.0625 mol |
| 1 M | 14.61 g | 0.25 mol |
Molarity uses the final volume of solution. Molality (mol/kg) needs the solvent mass instead, so it is not calculated from volume here.
What Is Molarity?
This molarity calculator finds the mass of solute to weigh, the molarity of a solution you already made, or the volume to prepare. It also solves C1V1 = C2V2 for any term and computes molar mass from a formula such as CuSO4·5H2O, with preparation steps and the full working.
Molarity is the amount of solute in moles divided by the volume of the whole solution in litres. IUPAC calls this quantity amount concentration and notes that older literature calls it molarity. Its unit is mol/L, the same as mol/dm³ because one litre is one cubic decimetre, and it is often written with the symbol M. A 1 M solution holds one mole of solute in each litre of solution.
The volume in the definition is the final volume of solution, not the volume of solvent you pour in. Dissolving 58.44 g of NaCl in 1 L of water gives a total volume that is not exactly 1 L, so the result is not exactly 1 M. To make exactly 1 M, dissolve the salt in less water and then add water until the solution reaches 1 L.
Molarity Formula: Grams, Moles and Volume
Moles equal mass divided by molar mass (n = m ÷ M), so the molarity formula can be rearranged to solve for any one of mass, molarity or volume. These three relations sit behind the Solve for menu.
Molarity to grams: 0.5 M NaCl in 250 mL
This is the default example in the calculator. The mass concentration is 7.305 g ÷ 0.25 L = 29.22 g/L, which is 2.922 percent w/v.
Grams to molarity: 9 g NaCl in 1 L
Nine grams of sodium chloride per litre is 0.9 percent w/v, the strength of normal saline. From moles directly, 0.25 mol in 500 mL is 0.25 ÷ 0.5 L = 0.5 M.
Units of Molarity and mM to M Conversion
Each metric prefix step is a factor of 1,000. To convert millimolar to molar, divide by 1,000; to go from molar to micromolar, multiply by 1,000,000. So 0.5 M = 500 mM = 500,000 µM. The calculator accepts every value with its own unit and shows the conversion as the first lines of Your calculation.
| Unit | Name | mol/L | Example |
|---|---|---|---|
| M | molar | 1 | 0.5 M NaCl |
| mM | millimolar | 0.001 | 10 mM Tris = 0.01 M |
| µM | micromolar | 0.000001 | 500 µM = 0.0005 M |
| nM | nanomolar | 0.000000001 | 250 nM = 0.00000025 M |
Volumes follow the same pattern: 1 L = 1,000 mL = 1,000,000 µL, and 1 mL = 1 cm³. Mass works the same way: 1 g = 1,000 mg = 1,000,000 µg.
How to Make a 1 M Solution
To prepare a solution of known molarity from a solid, weigh the solute, dissolve it in part of the solvent and bring it to the final volume in a volumetric flask. The Duke University analytical chemistry lab manual on LibreTexts describes this sequence and mixes the finished solution by inverting the flask 20 times.
- Calculate the mass. Grams = molarity × litres × molar mass. For 1 L of 1 M glucose (C6H12O6, 180.156 g/mol) that is 180.16 g.
- Weigh and record. Note the actual mass so you can work out the true concentration if it differs from the target.
- Dissolve in less than the final volume. Use about 70 to 80 percent of the final volume of water in a beaker.
- Transfer and rinse. Pour the solution into the volumetric flask and rinse the beaker into the flask.
- Fill to the mark and mix. Add water until the bottom of the meniscus sits on the line, then stopper and invert.
Hydrates: copper sulfate pentahydrate
CuSO4·5H2O carries five water molecules per formula unit, so its molar mass is 249.677 g/mol instead of 159.602 g/mol for anhydrous CuSO4. For 500 mL of 0.1 M copper sulfate, weigh 0.1 × 0.5 × 249.677 = 12.48 g of the blue pentahydrate, or 7.980 g of the anhydrous salt. Weighing 7.980 g of the hydrate by mistake gives a solution 36 percent too weak, because water makes up 36.08 percent of the hydrate mass.
Buffers: 10 mM Tris in 1 L
Tris base (C4H11NO3) has a molar mass of 121.136 g/mol, so 1 L of 10 mM Tris needs 0.01 × 1 × 121.136 = 1.211 g. Adjusting the pH adds acid or base and changes the volume slightly, so set the pH before the final fill to the mark.
Dilution Calculator: C1V1 = C2V2
Adding solvent does not change the number of moles of solute, so moles before dilution equal moles after: C1 × V1 = C2 × V2. C1 is the stock concentration, V1 the volume of stock you take, C2 the target concentration and V2 the final volume. Rearranging gives V1 = C2V2 ÷ C1, which answers the most common question: how much stock do I need?
Units only need to match on each side, so you can keep both volumes in mL and both concentrations in mM. A second example: 200 mL of 0.25 M from a 2.5 M stock needs 0.25 × 200 ÷ 2.5 = 20 mL of stock and 180 mL of solvent.
A 1:10 dilution means 1 part stock in 10 parts total, which is 1 part stock plus 9 parts solvent. The calculator shows this split in the Parts tile, because mixing 1 part stock with 10 parts solvent gives a 1:11 dilution instead.
Serial dilution
A serial dilution repeats one dilution step to reach very low concentrations accurately. In a tenfold series, each tube receives one tenth of its final volume from the tube before plus nine tenths solvent. From a 1 M stock with 50 mL tubes, each step moves 5 mL into 45 mL of solvent.
| Tube | Concentration | Total dilution |
|---|---|---|
| 1 | 0.1 M | 1:10 |
| 2 | 10 mM | 1:100 |
| 3 | 1 mM | 1:1,000 |
| 4 | 100 µM | 1:10,000 |
| 5 | 10 µM | 1:100,000 |
| 6 | 1 µM | 1:1,000,000 |
Molar Mass Calculator From a Chemical Formula
Molar mass is the mass of one mole of a substance in grams per mole, the sum of the standard atomic weights of every atom in the formula. The Molar mass mode reads element symbols, subscripts, parentheses, square brackets and a hydrate dot, and uses the 2024 abridged standard atomic weights from the IUPAC Commission on Isotopic Abundances and Atomic Weights (CIAAW).
| Compound | Formula | Molar mass (g/mol) | Grams for 1 L of 0.1 M |
|---|---|---|---|
| Sodium chloride | NaCl | 58.44 | 5.844 |
| Sodium hydroxide | NaOH | 39.997 | 4.000 |
| Glucose | C6H12O6 | 180.156 | 18.02 |
| Sucrose | C12H22O11 | 342.297 | 34.23 |
| Tris base | C4H11NO3 | 121.136 | 12.11 |
| Calcium chloride dihydrate | CaCl2·2H2O | 147.008 | 14.70 |
| Copper sulfate pentahydrate | CuSO4·5H2O | 249.677 | 24.97 |
Symbols are case sensitive: Co is cobalt but CO is carbon monoxide, so the parser rejects lowercase input such as nacl instead of guessing. A subscript after a closing bracket multiplies everything inside it, and a number in front of a hydrate part, such as the 5 in 5H2O, multiplies that whole part.
Molarity vs Molality vs Normality
| Measure | Definition | Unit | Temperature dependent |
|---|---|---|---|
| Molarity | Moles of solute per litre of solution | mol/L (M) | Yes, slightly |
| Molality | Moles of solute per kilogram of solvent | mol/kg | No |
| Normality | Equivalents per litre of solution | eq/L (N) | Yes, slightly |
Molality needs the mass of solvent, which you cannot get from the solution volume without the density. That is why this calculator reports molarity and does not estimate molality. Volume measures shift slightly with temperature because liquids expand, while mass based molality does not.
Normality is molarity times the number of reacting equivalents per formula unit. In a full acid base neutralization, 1 M H2SO4 supplies 2 moles of H⁺ per litre, so it is 2 N, while for NaCl the factor is 1. Because the factor depends on the reaction, the same solution can have more than one normality.
Percent Solution to Molarity
A percent w/v solution holds that many grams of solute in every 100 mL of solution, so multiplying by 10 gives grams per litre. Divide grams per litre by the molar mass to get molarity.
Percent w/w (by mass) and percent v/v (by volume) are different measures. Converting a percent w/w value, such as the strength printed on a concentrated acid bottle, to molarity also needs the solution density.
How to Use the Calculator
- Mass, volume, molarity. Pick what to solve for, then enter the solute, its molar mass and the two known values with units.
- Dilution. Pick the unknown among C1, V1, C2 and V2 and enter the other three.
- Molar mass. Type a formula, then press Use this molar mass to carry it into the first mode.
- Examples. The chips under the form load real cases, from saline to copper sulfate.
Common Mistakes
- Using solvent volume. Molarity uses the final solution volume.
- Skipping mL to L. 250 mL is 0.25 L; entering 250 L gives 1,000 times the mass.
- Ignoring hydrate water. CuSO4·5H2O needs about 56 percent more mass than CuSO4.
- Reading 1:10 as 1 + 10. It is 1 part stock plus 9 parts solvent.
- Lowercase formulas. Write NaCl, not nacl.
Frequently Asked Questions
How do you calculate molarity?
Molarity is moles of solute divided by litres of solution: M = n ÷ V. If you start from a mass, first divide the mass in grams by the molar mass in g/mol to get moles. For example, 9 g of NaCl ÷ 58.44 g/mol = 0.154 mol, and dissolving that in enough water to make 1 L gives 0.154 M, which is 0.9 percent saline. Always use the final volume of the solution in litres, not the volume of water you added, and convert millilitres by dividing by 1,000.
How many grams do I need to make a 1 M solution?
Multiply the molarity by the volume in litres and by the molar mass: grams = M × L × g/mol. For a 1 M solution in 1 L, the mass in grams equals the molar mass, so 1 L of 1 M NaCl needs 58.44 g and 1 L of 1 M glucose needs 180.16 g. For 100 mL of 1 M glucose, 1 × 0.1 × 180.156 = 18.02 g. Dissolve the solid in less than the final volume, transfer it to a volumetric flask and fill to the mark.
What is the C1V1 = C2V2 dilution formula?
C1V1 = C2V2 says the moles of solute stay the same when you add solvent. C1 and V1 are the stock concentration and the volume of stock you take, and C2 and V2 are the target concentration and the final volume. To make 50 mL of 0.1 M from a 1 M stock, V1 = 0.1 × 50 ÷ 1 = 5 mL. Pipette 5 mL of stock and add solvent to reach 50 mL, which is 45 mL of solvent. The formula works with any units as long as both sides match, but it does not apply to molality.
What is the difference between molarity and molality?
Molarity (M, mol/L) is moles of solute per litre of solution, so it depends on volume and changes slightly with temperature as the liquid expands. Molality (mol/kg) is moles of solute per kilogram of solvent, so it uses masses only and does not change with temperature. To convert one into the other you need the density of the solution. In dilute water solutions near room temperature the two values are close, but they separate as the solution becomes more concentrated. This calculator computes molarity and does not estimate molality from volume.
How do you convert mM to M?
Divide millimolar by 1,000 to get molar, because 1 M = 1,000 mM = 1,000,000 µM = 1,000,000,000 nM. For example, 250 mM is 0.25 M, and 10 mM Tris is 0.01 M. Going the other way, multiply molar by 1,000 to get mM, so 0.5 M is 500 mM or 500,000 µM. Enter the value with its own unit in the calculator and it converts to mol/L before multiplying by the volume in litres and the molar mass.
Sources & References
- IUPAC. amount concentration. Compendium of Chemical Terminology (Gold Book), online version 5.0.0, 2025 (definition, units mol/L and mol/dm³, symbol M, older name molarity). goldbook.iupac.org
- IUPAC. molality. Compendium of Chemical Terminology (Gold Book), online version 5.0.0, 2025 (amount of solute divided by the mass of solvent). goldbook.iupac.org
- Commission on Isotopic Abundances and Atomic Weights (CIAAW). Abridged Standard Atomic Weights 2024 (all atomic weights used by the molar mass parser). ciaaw.org
- Bureau International des Poids et Mesures (BIPM). SI base unit: mole (mol) (exact value of the Avogadro constant). bipm.org
- National Institute of Standards and Technology (NIST). CODATA Value: Avogadro constant, 2022 CODATA recommended values. physics.nist.gov
- Haas, K. Preparing Solutions. Duke University CHEM 401L Analytical Chemistry Lab Manual, Chemistry LibreTexts (stock solutions, dilution equation, glassware choice). chem.libretexts.org
- University of York, Department of Chemistry. Chemistry Teaching Labs: Preparing solutions via dilution (C1V1 = C2V2 method and heat on dilution). chemtl.york.ac.uk
Results are for education and planning. Follow your lab safety procedures and the safety data sheet (SDS) for every chemical. Every number on this page was recomputed with the same formulas the calculator uses. Methodology reviewed: 2026.