Convert between moles and a number of entities
Avogadro’s number calculator connects amount of substance to a count of specified elementary entities. Choose moles to entities or entities to moles, enter the known value, and name the entity as atoms, molecules, ions, formula units, or another clearly defined object. The calculation uses the exact SI Avogadro constant 6.02214076 × 10²³ per mole.
One mole always corresponds to that many named entities, but the entity must be stated. One mole of oxygen atoms and one mole of O2 molecules contain the same number of entities while the molecular sample contains twice as many oxygen atoms. Keeping the entity label beside the result prevents a correct multiplication from being attached to the wrong physical count.
Use the exact Avogadro constant
For moles to entities, multiply n by NA. For entities to moles, divide N by NA. The mole is defined so the Avogadro constant is exact rather than a measured value with uncertainty. Scientific notation is preserved because ordinary decimal expansion would hide the scale and make transcription errors more likely.
For example, 0.25 mol contains 1.50553519 × 10²³ entities. Dividing that result by 6.02214076 × 10²³ mol⁻¹ returns 0.25 mol. This round trip is a useful check on operation direction. A larger mole amount must always produce a proportionally larger entity count when the entity definition stays unchanged.
Choose atoms, molecules, ions, or formula units
Use molecules for a molecular substance such as H2O or CO2, formula units for an ionic solid such as NaCl, atoms for an elemental atom count, and ions when the problem specifically counts ions. The Other entities label is appropriate only when the object has already been defined, such as electrons or particles in a stated model.
The calculator does not inspect a chemical formula to multiply atoms inside each molecule or formula unit. To find oxygen atoms in a number of H2O molecules, first find the molecule count, then multiply by one oxygen atom per molecule. To find all atoms, multiply each element count and add them. Preserve that second stoichiometric step in the written solution.
Check exponents and measurement precision
When multiplying by NA, an amount near one mole should produce an entity count near 10²³. When dividing an ordinary laboratory-scale entity count by NA, the mole result is often much smaller than the raw count. Check exponent addition or subtraction before comparing coefficients. A sign error in an exponent can change the result by powers of ten while leaving familiar leading digits.
Although NA is exact, an experimental mole amount is not necessarily exact. The final significant figures should reflect the measured mass, molar mass, volume, or other quantity used to obtain moles. This page performs only the final count conversion and does not add uncertainty that was not supplied. Keep the source measurement and unit with any copied answer.
Counting limits and private use
The conversion does not calculate molar mass, mass, concentration, gas volume, charge, or formula-specific atom counts. Zero is accepted as a real value, while an empty field is not changed into zero. Extremely small or large values that collapse outside the supported numerical range are rejected instead of being displayed as false zero or infinity.
The values are calculated in the current browser tab. NexaCurrent does not upload the quantities, formulas, chemical names, element choices, or other information entered here, and no account is needed. Copying is a deliberate action after the answer and working are visible. Refreshing or leaving the page clears the current calculation, so keep a copied result if it is needed for later study.