The amount of substance in moles is the sample mass divided by its molar mass: n = m ÷ M. For example, 36.03 g of water at 18.015 g/mol is 2 mol. Multiply moles by the Avogadro constant, 6.02214076 × 10^23, to get the number of molecules, here about 1.2044 × 10^24.
Students balancing equations, lab technicians weighing reagents and teachers checking homework all need to move between grams, moles and particle counts. This calculator handles three directions: moles from a weighed mass, the mass needed for a target number of moles, and moles from a count of atoms or molecules. Alongside the answer it shows the amount in millimoles and the particle count from the Avogadro constant, plus the one-line working so you can copy it into a lab report. Results are given to five significant figures; very large or small values switch to scientific notation. One limit: you supply the molar mass yourself, so a wrong formula weight (for example forgetting water of crystallisation in CuSO₄·5H₂O) carries straight into the answer.
Pick moles from mass, mass from moles, or moles from particles.
Type the formula weight in g/mol, such as 58.44 for NaCl. The particle mode does not need it.
Give the mass in grams, the amount in moles, or the particle count (3.01e23 style notation works).
The result, millimoles, particle count and the formula with your numbers appear as you type.
Result Result: 2 mol
Amount (moles): 2 mol
Amount (millimoles): 2000 mmol
Particles (Avogadro): 1.2044 × 10^24
Water has a molar mass of 18.015 g/mol, so 36.03 g holds exactly 2 mol, about 1.2 × 10^24 molecules.
Result Result: 0.17112 mol
Amount (moles): 0.17112 mol
Amount (millimoles): 171.12 mmol
Particles (Avogadro): 1.0305 × 10^23
10 ÷ 58.44 gives 0.17112 mol, or 171 mmol, of NaCl.
Result Result: 22.005 g
Amount (moles): 0.5 mol
Amount (millimoles): 500 mmol
Particles (Avogadro): 3.0111 × 10^23
Half a mole of carbon dioxide at 44.01 g/mol weighs 22.005 g.
n = m ÷ M; m = n × M; N = n × NA, NA = 6.02214076 × 10^23 mol⁻¹
nmMNNASince the 2019 SI redefinition, one mole contains exactly 6.02214076 × 10^23 specified entities, so NA is a fixed number rather than a measured one. Molar mass in g/mol equals the relative formula mass, which lets a balance reading in grams be turned into moles by a single division. Particles are converted with the same constant in either direction.
A mole is the SI unit of amount of substance. Since 20 May 2019 it is defined as exactly 6.02214076 × 10^23 elementary entities, such as atoms, molecules, ions or electrons.
Add the standard atomic weights of every atom in the formula. For water that is 2 × 1.008 + 15.999 = 18.015 g/mol; for sodium chloride 22.990 + 35.453 = 58.44 g/mol.
It depends on the substance: one mole has a mass in grams equal to its molar mass. One mole of carbon-12 is 12 g, one mole of water about 18.015 g, and one mole of glucose about 180.16 g.
Even a milligram of substance contains around 10^19 molecules, so counts are printed as a coefficient times a power of ten, for instance 1.2044 × 10^24, to keep five significant figures readable.
Yes. The mole counts any specified entity. Enter the molar mass of the entity you mean, such as 35.45 g/mol for chloride ions, and the particle count refers to that entity.
One millimole is one thousandth of a mole. Clinical chemistry and small-scale lab work often quote mmol, so the tool lists both: 0.17112 mol is 171.12 mmol.
Using this tool in an assignment, article or report? Copy a citation, or a link for your website.
Tools Directory Editorial Team. (2026, October 23). Mole Calculator. Tools Directory. Retrieved October 26, 2026, from https://tools.milunir.com/chemistry/stoichiometry-and-reactions/mole-calculator/
Tools Directory Editorial Team. “Mole Calculator.” Tools Directory, 23 Oct. 2026, https://tools.milunir.com/chemistry/stoichiometry-and-reactions/mole-calculator/. Accessed 26 Oct. 2026.
Tools Directory Editorial Team. “Mole Calculator.” Tools Directory. Last modified October 23, 2026. Accessed October 26, 2026. https://tools.milunir.com/chemistry/stoichiometry-and-reactions/mole-calculator/.
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