Free · Stoichiometry calculators 🧪

Sample Mass, Moles & Molecule Count

Convert sample mass, molar mass, amount of substance and molecule count with scientific notation and selectable mass and mole units.

Formula & worked example
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Calculator inputs

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How to use this calculator

Enter the known values in the units shown. Results update as you type.
Where results are editable, change one to solve backwards. Lock a value to hold it fixed.
Use the worked example to check the method. Reset restores the starting fields.

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Inputs and results stay in this browser tab. Bookify does not upload or store the values you enter.

Formula and method

For a substance with molar mass 18 g/mol, a 36 g sample is 2 mol and contains 1.204428152 × 10²⁴ molecules.

Amount = mass / molar mass; molecule count = amount in mol × 6.02214076 × 10²³

Worked example

Enter these known values and leave the other values blank.

Sample mass: 36 g
Molar mass: 18 g/mol

Amount of substance: 2 mol
Number of molecules: 12.044 × 10²³

Assumptions and limitations

Use the molar mass of the molecules being counted. An ionic material may instead be described by formula units; the arithmetic counts whichever entities the entered molar mass represents.
The Avogadro constant is exactly 6.02214076 × 10²³ per mol. Mass, molar mass, amount and count must be positive.
Molecule-count entries are coefficients of the selected power of ten. Molar mass is entered directly; this tool does not infer composition or isotope abundance.

Common questions

Can I enter millimoles instead of moles?

Yes. Select mmol before entering the amount. One millimole is 0.001 mol and contains 6.02214076 × 10²⁰ entities.

References

The calculation equations, inverse formulas, units, and input rules were imported from this source. Bookify provides the interface and equation solver.

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