Molarity Calculator — Concentration & Dilution (M1V1=M2V2)

Calculate molarity from mass and molar mass, or solve any dilution variable with M1V1 = M2V2. Instant results for lab and homework chemistry.

July 14, 2026

Mass of Solute (g)

Molar Mass (g/mol)

Solution Volume

Volume Unit

Enter your own molar mass for the solute — this calculator doesn't look up periodic-table values for you.

Moles of Solute

0.1 mol

Molarity

0.2 M

Molarity (M) = moles of solute ÷ liters of solution. Dilution: M1V1 = M2V2, where M1/V1 describe the concentrated stock and M2/V2 describe the diluted final solution — solve for any one variable given the other three. This is standard intro-chemistry math; for precise lab work, always confirm your stock's exact concentration against its certificate of analysis.

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Reference Values

Last verified: Jul 11, 2026

Category	Range	What It Means	Status
Molarity formula ★	M = mol solute ÷ L solution	The core definition of molar concentration — moles of dissolved solute divided by the total volume of solution (not just the solvent) in liters.	★ Best
Dilution formula ★	M₁V₁ = M₂V₂	Relates a concentrated stock solution (M₁, V₁) to a diluted working solution (M₂, V₂). Solve for any one variable given the other three.	★ Best
Moles from mass	mol = mass (g) ÷ molar mass (g/mol)	Converts a weighed-out mass of solute into moles before applying the molarity formula. Molar mass must be looked up or calculated separately for your specific compound.	Good
Dilute / trace solutions	< 0.1 M	Common for physiological buffers, diluted indicators, and trace reagents used directly in an assay or reaction.	Good
Standard working solutions	0.1 M – 1 M	The most common range for titrants, buffers, and general-purpose lab reagents prepared for day-to-day use.	Good
Concentrated stock solutions	1 M – 6 M	Typical range for stock reagents (e.g., stock HCl or NaOH) that are diluted down before use, minimizing storage volume.	Okay
1:10 dilution (10×)	V₁ = V₂ ÷ 10	A common serial-dilution step — take 1 part stock and bring it up to 10 total parts with solvent to drop concentration by a factor of 10.	Good
1:100 dilution (100×)	V₁ = V₂ ÷ 100	Two consecutive 1:10 dilutions, or one direct 1:100 dilution — commonly used to bring a concentrated stock into a dilute working range.	Good

Source: Molarity and dilution formulas per standard general-chemistry convention (IUPAC definition of amount concentration); dilution-ratio and lab-concentration bands reflect common undergraduate and analytical-lab practice. See TopBlogTenz, "M1V1 = M2V2 Dilution in Chemistry," and Sigma-Aldrich Solution Dilution Calculator methodology. Always confirm exact stock concentration against the reagent's certificate of analysis for precise lab work.

Worked Examples

Molarity From a Weighed Mass (NaCl)

Mass: 5.85 g
Molar Mass: 58.5 g/mol
Volume: 0.500 L

0.2 M

Moles = 5.85 ÷ 58.5 = 0.1 mol. Molarity = 0.1 mol ÷ 0.500 L = 0.2 M.

Molarity From a Weighed Mass, Volume in mL (NaOH)

Mass: 4.0 g
Molar Mass: 40.0 g/mol
Volume: 250 mL

0.4 M

Moles = 4.0 ÷ 40.0 = 0.1 mol. 250 mL = 0.250 L, so Molarity = 0.1 ÷ 0.250 = 0.4 M.

Dilution — How Much Stock to Use

M1 (stock): 6.0 M
M2 (target): 0.5 M
V2 (final volume): 500 mL

V1 = 41.7 mL

V1 = (M2 × V2) ÷ M1 = (0.5 × 500) ÷ 6.0 = 41.7 mL. Measure out 41.7 mL of the 6.0 M stock and add solvent up to a total of 500 mL.

Dilution — Solving for the Resulting Concentration

M1 (stock): 2.0 M
V1 (stock volume): 50 mL
V2 (final volume): 200 mL

M2 = 0.5 M

M2 = (M1 × V1) ÷ V2 = (2.0 × 50) ÷ 200 = 0.5 M.

Dilution — How Much Water to Add

M1 (stock): 1.0 M
V1 (stock volume): 100 mL
M2 (target): 0.1 M

V2 = 1000 mL (add 900 mL water)

V2 = (M1 × V1) ÷ M2 = (1.0 × 100) ÷ 0.1 = 1000 mL total. Since you started with 100 mL of stock, add 1000 − 100 = 900 mL of solvent to reach 0.1 M.

How to Use This Calculator

1

Pick a mode

"Molarity From Mass" builds a concentration from a weighed solute; "Dilution Calculator" solves M1V1 = M2V2 for any one of the four variables.
2

For Molarity From Mass, enter mass, molar mass, and volume

Type the mass of solute in grams, its molar mass in g/mol, and the solution's total volume (choose liters or milliliters).
3

For Dilution, choose what to solve for

Tap M1, V1, M2, or V2 to select the unknown, then fill in the other three known values.
4

Read your result instantly

Molarity, moles, or the missing dilution variable updates live as you type — no submit button needed.
5

Check the solvent-to-add note

When solving for V2 or M2 with a starting stock volume entered, the calculator also shows how much solvent to add to reach your target.

What Each Value Means

Molarity (M) (mol/L): Molar concentration — the number of moles of solute dissolved per liter of total solution, written as mol/L or M.
Moles of Solute (mol): The amount of a substance measured in moles, calculated by dividing its mass by its molar mass.
M1V1 (stock side) (mol/L, mL): The concentration (M1) and volume (V1) of the concentrated stock solution before dilution.
M2V2 (diluted side) (mol/L, mL): The concentration (M2) and total final volume (V2) of the solution after solvent has been added.

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Frequently Asked Questions

What is the molarity formula?

Molarity (M) = moles of solute ÷ liters of solution. The unit is mol/L, usually written as M. If you're starting from a mass instead of moles, first convert: moles = mass (g) ÷ molar mass (g/mol), then divide by the solution's total volume in liters — not just the volume of solvent you added.

What is the M1V1 = M2V2 dilution formula and when do I use it?

M1V1 = M2V2 relates a concentrated stock solution (M1 concentration, V1 volume) to a diluted working solution (M2 concentration, V2 final volume). Use it any time you're diluting a stock reagent down to a weaker working concentration — for example, figuring out how much 6.0 M stock to measure out to make 500 mL of 0.5 M solution. Because moles of solute don't change during dilution (you're only adding solvent), the product of concentration and volume stays constant on both sides.

Does it matter if I use liters or milliliters?

Not for the dilution formula (M1V1 = M2V2), since mL on both sides cancels the same way liters would — this calculator's dilution tab works directly in mL. For the molarity-from-mass formula, though, the final division has to be in liters, since molarity is defined as moles per liter. This calculator handles that conversion for you when you select mL as your volume unit.

Why do I have to enter the molar mass myself?

Molar mass depends entirely on which compound you're dissolving — sodium chloride (NaCl) is 58.5 g/mol, sodium hydroxide (NaOH) is 40.0 g/mol, glucose is 180.2 g/mol, and so on. This calculator doesn't guess your compound, so you'll need to look up or calculate the molar mass (sum of atomic masses from the periodic table) for whatever you're weighing out before entering it here.

Can I dilute a solution to a higher concentration?

No — dilution only ever lowers concentration, because you're adding solvent, not removing it or adding more solute. If you try to solve for V1 with a target concentration (M2) higher than your stock concentration (M1), this calculator will flag it as invalid rather than return a nonsense negative or backwards volume. To increase concentration you'd need to evaporate solvent or dissolve additional solute, which is a different calculation entirely.