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Moles calculator

Compute the number of moles of a substance from its mass and molar mass.

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Molality calculatorCompute molality — moles of solute per kilogram of solvent — the concentration unit that, unlike molarity, does not change with temperature. Enter moles directly or a mass with its molar mass, plus the solvent mass, and it returns the molality in mol/kg.Normality calculatorCompute the normality of a solution — gram-equivalents of solute per litre. Enter equivalents directly or a mass with its molar mass and n-factor, plus the volume, and it returns the normality (N) and the equivalent molarity (M = N ÷ n-factor).Beer-Lambert law calculatorSolve the Beer-Lambert law A = ε·c·l for any variable — absorbance, molar absorptivity, concentration or path length. Central to spectrophotometry, it links how much light a solution absorbs to how concentrated it is. Pick what to solve for, enter the rest, and read the answer.Half-life calculatorCompute how much of a substance remains after a time, given its half-life.Molarity calculatorCompute the molar concentration of a solution from moles and volume.pH calculatorCompute the pH and pOH of a solution from the hydrogen ion concentration.Chemical Equation BalancerBalance any chemical equation instantly by solving the element matrix exactly — even tricky redox reactions.Dilution calculator (C1V1 = C2V2)Find the final volume needed to dilute a solution to a target concentration.

The Moles calculator turns Mass (g), Molar mass (g/mol) into Amount (mol), instantly and for free. For instance, with Mass (g) = 18 and Molar mass (g/mol) = 18.015 it returns Amount (mol) = 0.999.

How to use it

  1. Enter your values: Mass (g), Molar mass (g/mol).
  2. Read the result instantly: Amount (mol).

Frequently asked questions

What does the Moles calculator actually compute?

It takes Mass (g) and Molar mass (g/mol) and derives Amount (mol) from them. The calculation is live as you type, so the result updates on every change.

What information do I need to provide?

2 values: Mass (g) and Molar mass (g/mol). Nothing else is required — no account, no file upload.

Can you show a worked example?

With Mass (g) = 18 and Molar mass (g/mol) = 18.015, the calculator returns Amount (mol) = 0.999. Those figures come from running this exact tool, so you can reproduce them by entering the same values.

What happens if I enter larger values?

It moves a lot. Using Mass (g) = 20 and Molar mass (g/mol) = 36.03 instead, Amount (mol) goes from 0.999 to 0.555 — which is why it is worth testing a few scenarios rather than trusting a single figure.

What does it give for smaller values?

Scaled down to Mass (g) = 16 and Molar mass (g/mol) = 9.008, Amount (mol) comes out at 1.776. The relationship is worth checking at both ends before you rely on a single result.

When would I actually use this?

Preparing a solution at a stated concentration, working out how much of a reagent a reaction needs, and converting between mass, moles and volume.

What is the most common mistake?

Confusing molarity with molality. One is per litre of solution and the other per kilogram of solvent; they diverge as concentration rises, and only one of them is temperature-independent.

What is the difference between the Moles calculator and the Molality calculator?

This one returns Amount (mol); the Molality calculator returns Molality and Moles of solute used. That is the whole difference — open the one whose figure you need.

Is there a tool for the next step?

Normality calculator is the closest one after this: Compute the normality of a solution — gram-equivalents of solute per litre. Enter equivalents directly or a mass with its molar mass and n-factor, plus the volume, and it returns the normality (N) and the equivalent molarity (M = N ÷ n-factor).

Where do the figures come from, and how current are they?

Atomic masses are the IUPAC standard values. Results assume ideal behaviour and standard conditions unless the tool says otherwise — real solutions deviate, and lab work needs lab measurement.

Further reading

All guides →
ExplainerThe Ideal Gas Law Explained: PV = nRT, R in Every Unit, and Where It BreaksPV = nRT holds when the gas is dilute and far from condensing. The value of R depends entirely on the units you feed it, and the temperature is never in degrees Celsius.How-toHow to Calculate Molar Mass, Including Parentheses and HydratesMultiply each atomic weight by its subscript and add. The only three places the arithmetic goes wrong are a subscript after a closing bracket, the hydrate dot, and a capital letter typed as a lowercase one.How-toHow to Calculate a Dilution with C1V1 = C2V2Solve for the missing term, then convert the answer into a bench instruction. The step almost everyone skips is that the solvent you add is V2 minus V1, not V2.How-toHow to Calculate pH — And When the Weak-Acid Shortcut Stops WorkingFour routes for four kinds of solution, each worked with real numbers. Including the part most pages leave out: the square-root formula for a weak acid is an approximation with a validity limit, and it fails quietly.ExplainerHow Half-Life Works: What Is Left After 1, 3 and 10 Half-LivesOne half-life leaves 50%, three leave 12.5%, ten leave less than a tenth of a percent. The formula is a single line — the part worth understanding is why the answer never reaches zero.How-toHow to Solve Stoichiometry Problems: Grams to Moles to Ratio to GramsEvery problem in the chapter is the same four moves. The mole ratio is the hinge, and it is the step students lose — worked here end to end, limiting reactant and percent yield included.