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Molarity Calculator

Work out the mass to weigh, the concentration, the volume or the molar mass of any solution in seconds. Type a formula or name and the molar mass fills in for you, then follow the step-by-step recipe. A C1V1 = C2V2 dilution calculator and a percent to molarity converter are built in.

Calculate molarity
  • Solve for any value
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Molarity, dilution and percent to molarity calculator

Mass, concentration and volume

Solve for

g/mol
Result

Mass to weigh

7.305g

Moles of solute
–
Mass concentration
–
Molar mass used
–
Final volume
–

How to prepare it

    Why it is better

    A molarity calculator that does the whole job

    Most molarity calculators expect you to know the molecular weight, leave a box blank and press a button. This one removes those steps and tells you exactly how to make the solution.

    Solve for any value

    Pick mass, concentration, volume or molar mass. The result field is highlighted and every answer updates as you type.

    Molar mass from a formula or name

    Type NaCl, Tris, HEPES or CuSO4*5H2O and the molar mass is calculated for you, including hydrates and brackets.

    Lab units built in

    Switch between kg, g, mg, µg and ng, between M, mM, µM, nM and pM, and between L, mL and µL without converting by hand.

    A recipe, not just a number

    Get clear steps: how much to weigh, how much solvent to start with and what flask to fill, plus the equation with your values.

    Dilution calculator included

    Use C1V1 = C2V2 to find the stock volume, diluent and dilution factor, with a visual mix bar.

    Percent to molarity

    Convert concentrated acids and bases from % w/w and density to molarity, then send the result straight to the dilution tab.

    How to use

    How to use the molarity calculator

    Most solutions take less than ten seconds. Follow these four steps.

    1. Choose what to solve for

      Select Mass to find how much solute to weigh. Alternatively, choose Concentration, Volume or Molar mass.

    2. Enter the compound

      Type a formula or a common name. The molar mass appears automatically, but you can also type your own value.

    3. Fill in the other values

      Enter the known quantities and pick their units. The highlighted result field updates on every keystroke.

    4. Follow the recipe

      Read the step-by-step preparation, check the equation and copy the result into your lab notebook.

    The formula

    Molarity formula: how to calculate molarity

    Molarity (M) is the number of moles of solute per liter of solution. Its unit is mol/L, usually written as M. So a 1 M solution contains one mole of solute in every liter of the final solution.

    M = n ÷ V = m ÷ (MW × V)n = moles, m = mass in g, MW = molar mass in g/mol, V = volume in L

    Rearrange the same equation to find the mass you need: m = M × V × MW. If you only know the formula, find MW first with our molar mass calculator, or let this tool do it for you.

    How to prepare a solution of known molarity

    1. Calculate the mass of solute with m = M × V × MW.
    2. Weigh the solute and dissolve it in about 80% of the final volume of solvent.
    3. Transfer the solution to a volumetric flask of the final volume.
    4. Add solvent up to the mark, then cap and invert to mix.

    Dissolving in less solvent first matters because the solute itself takes up volume. If you add it to the full volume, the final concentration will be slightly low.

    Example 1

    Grams of NaOH for 500 mL of 0.1 M

    1. Convert the volume: 500 mL = 0.5 L.
    2. Use the molar mass of NaOH: 39.997 g/mol.
    3. Multiply: 0.1 × 0.5 × 39.997 = 2.000 g.
    Mass of NaOH to weigh2.000 g

    Example 2

    Molarity of 5.85 g NaCl in 250 mL

    1. Find the moles: 5.85 ÷ 58.44 = 0.1001 mol.
    2. Convert the volume: 250 mL = 0.25 L.
    3. Divide: 0.1001 ÷ 0.25 = 0.400 M.
    Molarity of the solution0.400 M

    Dilutions

    Dilution calculator: using C1V1 = C2V2

    When you dilute a stock solution, the number of moles stays the same. Only the volume changes. That gives the dilution equation, where C1 and V1 describe the stock and C2 and V2 describe the final solution.

    V1 = (C2 × V2) ÷ C1Use the same concentration units for C1 and C2, and the same volume units for V1 and V2.

    For example, to make 100 mL of 0.1 M from a 1 M stock, V1 = 0.1 × 100 ÷ 1 = 10 mL. Then add 90 mL of water to reach 100 mL. The dilution factor is 10, often written as 1:10.

    Tips for accurate dilutions

    1. Pipette the stock into the flask first, then add diluent up to the final volume.
    2. For dilutions above 1:100, use two serial steps to reduce pipetting error.
    3. For concentrated acids, always add the acid slowly to water.

    Reference table

    Molarity of concentrated acids and bases

    Commercial reagents are sold as a percent by weight. To convert, use M = (% × density × 10) ÷ MW. The table below uses typical assay and density values.

    Molarity of common concentrated reagents
    Reagent% w/wDensity (g/mL)MolaritymL for 1 L of 1 MAction
    Hydrochloric acidHCl371.1912.08 M82.8
    Sulfuric acidH2SO4981.8418.39 M54.4
    Nitric acidHNO3701.4215.77 M63.4
    Acetic acid (glacial)CH3COOH99.71.04917.42 M57.4
    Ammonia solutionNH3 (as ammonium hydroxide)280.9014.80 M67.6
    Phosphoric acidH3PO4851.68514.62 M68.4

    Values are approximate. Check the assay and density on your bottle before preparing solutions.

    Lab cheat sheet

    Mass needed for common lab solutions

    The grams of solute needed for two common preparations. Select Load to open any row in the calculator and change the volume or concentration.

    Grams of solute needed for common laboratory solutions
    CompoundMolar mass (g/mol)1 L of 1 M100 mL of 0.1 MAction
    Sodium chlorideNaCl58.44058.44 g0.5844 g
    Potassium chlorideKCl74.54874.55 g0.7455 g
    Sodium hydroxideNaOH39.99740.00 g0.4000 g
    Calcium chloride dihydrateCaCl2·2H2O147.008147.01 g1.4701 g
    Magnesium chloride hexahydrateMgCl2·6H2O203.295203.30 g2.0330 g
    Magnesium sulfate heptahydrateMgSO4·7H2O246.466246.47 g2.4647 g
    Sodium bicarbonateNaHCO384.00684.01 g0.8401 g
    Potassium dihydrogen phosphateKH2PO4136.084136.08 g1.3608 g
    Disodium hydrogen phosphateNa2HPO4141.957141.96 g1.4196 g
    Tris baseC4H11NO3121.136121.14 g1.2114 g
    HEPESC8H18N2O4S238.302238.30 g2.3830 g
    EDTA disodium dihydrateC10H14N2Na2O8·2H2O372.238372.24 g3.7224 g
    GlucoseC6H12O6180.156180.16 g1.8016 g
    Sodium dodecyl sulfate (SDS)C12H25NaO4S288.378288.38 g2.8838 g

    Key terms

    Molarity vs molality vs normality

    These three units all describe concentration, but each one is defined differently. Choosing the right one matters for accurate results.

    Molarity (M)

    Moles of solute per liter of solution. It is the standard unit for preparing lab solutions, but it changes slightly with temperature because liquids expand.

    Molality (m)

    Moles of solute per kilogram of solvent. Because it uses mass, it does not change with temperature, so it is used for boiling point and freezing point problems.

    Normality (N)

    Equivalents per liter. For example, 1 M H2SO4 is 2 N in acid-base reactions because each molecule releases two H+ ions.

    Benefits

    Who uses this molarity calculator

    Everything runs in your browser, so nothing is uploaded. It is free, needs no sign-up and works on any phone at the bench.

    Chemistry students

    Check homework, see the equation with your numbers in it and learn how molarity, moles and volume connect.

    Lab technicians

    Prepare buffers and reagents quickly, with the exact mass to weigh and a clear recipe you can follow step by step.

    Biology researchers

    Work in mM, µM and µL for stock solutions, enzyme assays and cell culture media without unit errors.

    Pharmacy and industry

    Convert concentrated reagents from percent to molarity and plan dilutions for quality control and production.

    FAQ

    Molarity calculator FAQs

    What is molarity?

    Molarity is the number of moles of solute dissolved in one liter of solution. It is written as M or mol/L. For example, a 1 M solution of sodium chloride contains 58.44 g of NaCl in every liter.

    How do you calculate molarity?

    Divide the moles of solute by the volume of solution in liters. If you start from grams, divide the mass by the molar mass first. For example, 5.85 g of NaCl in 250 mL gives 5.85 ÷ 58.44 ÷ 0.25 = 0.400 M.

    How many grams do I need to make a solution?

    Multiply the molarity by the volume in liters and the molar mass. For 500 mL of 0.1 M NaOH, that is 0.1 × 0.5 × 39.997 = 2.000 g. Choose Mass in the calculator to get this instantly.

    What does C1V1 = C2V2 mean?

    It is the dilution equation. The stock concentration times the stock volume equals the final concentration times the final volume, because the moles of solute do not change. Solve it for any one value when you know the other three.

    What is the molarity of concentrated HCl?

    Concentrated hydrochloric acid at 37% w/w with a density of 1.19 g/mL is about 12.1 M. You need roughly 82.8 mL of it to make 1 L of 1 M HCl.

    What is the difference between molarity and molality?

    Molarity divides moles by liters of solution, while molality divides moles by kilograms of solvent. As a result, molality does not change with temperature, but molarity does.

    What do mM, µM and nM mean?

    They are smaller units of molarity. 1 mM (millimolar) is 0.001 M, 1 µM (micromolar) is 0.000001 M and 1 nM (nanomolar) is 0.000000001 M. The calculator converts between them automatically.

    Should I dissolve the solute in the full volume of water?

    No. Dissolve it in about 80% of the final volume, then top up to the mark in a volumetric flask. The solute takes up space, so adding it to the full volume makes the concentration slightly lower than planned.

    Ready for the bench

    Make every solution right the first time

    From a simple salt solution to a serial dilution of concentrated acid, this molarity calculator gives you the numbers and the method in one place. Bookmark it for your next prep.

    Calculate molarity now
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