Last updated: July 3, 2026
Mole Calculator
Creators
Dharmendra SinghReviewers
Creators
Dharmendra SinghReviewers
Quick Answer
The mole calculator computes amount of substance from mass with molar mass, from particles using Avogadro's constant, or from ideal-gas volume at STP. It also converts moles back to particles, grams when molar mass is supplied, and litres at STP for gases.
To calculate moles, divide grams by molar mass, divide particles by Avogadro's constant, or divide gas volume at STP by 22.414 litres per mole.
Key Takeaways
- The mole is the SI unit for amount of substance and counts 6.02214076×10²³ specified entities.
- Mass converts to moles with n = m / M, so molar mass must match the exact substance.
- Particles convert to moles with n = N / N_A and moles convert back with N = nN_A.
- Ideal gases at STP use V = n × 22.414 L, but non-STP gases need gas-law corrections.
- Moles are the common language of balanced equations, concentration, yield, and gas calculations.
Creators
Dharmendra SinghReviewers
Creators
Dharmendra SinghReviewers
Formula
n = m / M; N = n × N_A; V_STP = n × 22.414 L/mol
Where:
- n=Amount of substance(mol)
- m=Mass(g)
- M=Molar mass(g/mol)
- N=Number of particles(particles)
- N_A=Avogadro constant(particles/mol)
- V_STP=Ideal gas volume at STP(L)
Worked Examples
Water: 18.015 g is 1 mol
A water sample whose mass equals water's molar mass contains one mole of molecules.
- 1Use n = m ÷ M.
- 2Substitute m = 18.015 g and M = 18.015 g/mol.
- 3n = 1 mol, then N = 1 × 6.022×10²³ molecules.
Avogadro-number particles
A count of 6.022×10²³ specified entities is one mole to the usual classroom precision.
- 1Use n = N ÷ N_A.
- 2Substitute N = 6.022×10²³ and N_A = 6.022×10²³ mol⁻¹.
- 3n = 1 mol.
44.8 L of ideal gas at STP
Gas volume at STP converts through 22.414 L/mol.
- 1Use n = V_STP ÷ 22.414.
- 2Substitute V_STP = 44.8 L.
- 3n = 44.8 ÷ 22.414 = 1.9988 mol, approximately 2 mol.
Half a mole as particles
Convert 0.5 mol into a particle count.
- 1Use N = n × N_A.
- 2Substitute n = 0.5 mol.
- 3N = 0.5 × 6.022×10²³ = 3.011×10²³ particles.
Two moles of gas at STP
Convert moles of an ideal gas to litres at STP.
- 1Use V_STP = n × 22.414 L/mol.
- 2Substitute n = 2 mol.
- 3V_STP = 44.828 L, which rounds to 44.83 L.
Introduction
The mole calculator treats the mole as the central bridge between the microscopic world of atoms, molecules, ions, or formula units and macroscopic measurements such as grams and litres. It can calculate moles from mass plus molar mass, from a particle count using Avogadro's constant, from ideal-gas volume at STP, or start from moles and convert outward. If you need molar mass first, use the molar mass calculator; if your next step is solution preparation, continue with the molarity calculator. The definitions align with the BIPM SI Brochure and the NIST Avogadro constant.
What is a mole?
A mole is the SI unit for amount of substance. One mole contains exactly 6.02214076×10²³ specified elementary entities, so it works like a chemist's counting unit. The entities must be named: molecules for water, atoms for helium, ions for chloride, or formula units for sodium chloride crystals.
- Microscopic side:
particles are counted by Avogadro's constant.
- Macroscopic side:
mass is measured on a balance and converted with molar mass.
- Gas side:
ideal gases at STP use the molar volume bridge.
- Stoichiometry side:
balanced equations compare mole ratios.
Choosing the right calculation strategy
The calculator supports several strategies. Use mass when you know grams and g/mol. Use particles when the problem gives atoms, molecules, ions, or formula units. Use STP volume for an ideal gas at standard temperature and pressure. Use moles when you already know n and want equivalent particles, grams, or gas volume.
| Known input | Required extra data | Relation |
|---|---|---|
| Mass in grams | Molar mass | n = m / M |
| Particles | None | n = N / N_A |
| Gas volume at STP | Ideal-gas STP assumption | n = V / 22.414 |
| Moles | Optional molar mass | N = nN_A; m = nM |
Mass to moles and back
The mass bridge uses molar mass, M, in grams per mole. For water, M = 18.015 g/mol, so 18.015 g is 1 mol and 36.030 g is 2 mol. This is broader than a grams-to-moles-only workflow because the result can immediately be translated into particles or gas volume. For focused weighing problems, compare with the grams to moles calculator.
Mass conversion is substance-specific. The same 18.015 g is 1 mol of water but only about 0.100 mol of glucose.
Particles to moles with Avogadro's constant
Particle conversion uses N = n × N_A and its rearrangement n = N / N_A. The exact SI value is 6.02214076×10²³ mol⁻¹, while many classroom problems use 6.022×10²³. Authoritative terminology is summarized in the IUPAC Gold Book.
Always state the entity being counted; 1 mol of O atoms and 1 mol of O₂ molecules contain different numbers of oxygen atoms.
Ideal-gas volume at STP
For an ideal gas at STP, this calculator uses 22.414 L/mol. That gives 44.8 L ÷ 22.414 L/mol = 1.9988 mol, which is essentially 2 mol for many teaching problems. Outside STP, use the ideal gas law or a gas-law calculator because volume changes with temperature and pressure.
Use litres, not millilitres, with 22.414 L/mol.
Apply the STP bridge only for gases, not liquids or solids.
Real gases can deviate from ideal behavior at high pressure or low temperature.
Round final gas answers according to the measured volume.
Why moles are central in stoichiometry
Balanced chemical equations compare amounts in moles, not grams or particle counts directly. A typical workflow converts grams to moles, applies the balanced-equation mole ratio, and then converts product moles into grams or volume. That makes this tool a natural companion to the theoretical yield calculator, concentration tools, and limiting-reactant methods.
| Task | Mole role |
|---|---|
| Weigh a reactant | Convert g to mol with molar mass |
| Count particles | Convert entities to mol with N_A |
| Measure gas at STP | Convert L to mol with molar volume |
| Predict product | Use balanced coefficients as mole ratios |
Common mistakes to avoid
Most mole errors come from mixing units, using the wrong molar mass, applying the STP gas volume to non-gases, or confusing particles with moles. Keep extra digits during intermediate steps, then round the final result. Use standard references such as LibreTexts general chemistry for worked stoichiometry context.
Do not use grams alone; mass-to-moles also needs molar mass.
Do not call every particle a molecule; ionic solids use formula units.
Do not use 22.414 L/mol away from STP without a gas-law correction.
Do not round 1.9988 mol too early if later steps require precision.
Quick Reference Card
Mole — Quick Reference
Quick reference • Mole Calculator
n = m/M; N = n×6.022×10²³; V_STP = n×22.414 LValid range: Use positive finite values; mass mode requires a positive molar mass, and STP volume applies only to ideal gases at STP.
Common Values
⚠ Watch Out
- •Mass-to-moles conversion is impossible without the correct molar mass.
- •The 22.414 L/mol shortcut assumes an ideal gas at STP only.
- •Name the counted entity: atoms, molecules, ions, or formula units.
- •Avoid rounding intermediate moles before using reaction coefficients.
Pro Tips
- →Use scientific notation, such as 6.022e23, for very large particle counts.
- →Check mass-mode answers by confirming grams divided by g/mol leaves mol.
- →For gases away from STP, switch to PV = nRT rather than the molar-volume shortcut.
- →Pair mole results with theoretical yield or molarity tools for multi-step chemistry problems.
FAQs
How do I calculate moles from grams?
Divide mass in grams by molar mass in g/mol: n = m / M. For 18.015 g of water with M = 18.015 g/mol, n = 1 mol.
How many particles are in one mole?
One mole contains exactly 6.02214076×10²³ specified entities in the SI. This calculator displays the rounded classroom value 6.022×10²³ in examples.
How do I convert particles to moles?
Divide the number of particles by Avogadro's constant. For 6.022×10²³ particles, n = 1 mol.
What volume does one mole of gas occupy at STP?
For an ideal gas at STP, one mole occupies about 22.414 L. Therefore 2 mol occupies about 44.83 L.
Can I use the STP volume relation for liquids or solids?
No. The 22.414 L/mol bridge applies to ideal gases at STP. Liquids and solids need density or molar volume data instead.
Why is the mole called a bridge?
It connects measurable laboratory quantities such as grams and litres to microscopic counts of atoms, molecules, ions, or formula units, and it is the unit used in balanced chemical equations.