Molar Mass & Mole Calculator
Type a formula to get its molar mass, element-by-element breakdown, and mole–gram–particle conversions.
Element breakdown
| Element | Atoms | Atomic mass | Subtotal (g/mol) | Mass % |
|---|---|---|---|---|
| O | 1 | 15.999 | 15.999 | 88.81% |
| H | 2 | 1.008 | 2.016 | 11.19% |
| Total | 18.015 | 100% | ||
Mass composition
mol ⇄ gram ⇄ particles
Edit any field; the others update automatically.
One mole always contains 6.022 × 10²³ particles — Avogadro's number — no matter the substance.
About this calculator
Molar mass is the mass of one mole of a substance, expressed in grams per mole (g/mol). It is numerically equal to the sum of the atomic masses of every atom in the chemical formula. This tool parses any formula you type — including parentheses, subscripts and hydrate dots like CuSO4·5H2O — looks up each element's standard atomic weight, and shows the molar mass plus how every element contributes to the total mass. It then lets you convert freely between mass (g), amount of substance (mol) and the actual number of particles.
How to use
- 1 Type a chemical formula, or tap one of the example presets (H2O, NaCl, C6H12O6…).
- 2 Read the molar mass in g/mol and the per-element breakdown table.
- 3 Check the donut chart to see each element's share of the total mass.
- 4 Enter a value in grams, moles, or particles — the other two update instantly.
How it works
The formula is parsed atom by atom. Each element symbol is matched to its standard atomic weight, multiplied by its subscript (and any bracket multipliers), and summed to give the molar mass M. The conversions use two simple relations: • Amount of substance: n = m / M (moles = grams ÷ molar mass) • Particle count: N = n × Nₐ, where Nₐ = 6.02214076 × 10²³ mol⁻¹ (Avogadro's number). So 1 mol of water (M = 18.015 g/mol) weighs 18.015 g and contains 6.022 × 10²³ molecules.
Frequently asked questions
What is molar mass?
Molar mass is the mass of one mole of a substance in grams per mole (g/mol). It equals the sum of the atomic masses of all atoms in the chemical formula. For example, water (H2O) has a molar mass of about 18.015 g/mol.
How do I convert grams to moles?
Divide the mass in grams by the molar mass: n = m / M. For example, 36.03 g of water ÷ 18.015 g/mol = 2 moles.
What is Avogadro's number?
Avogadro's number, 6.02214076 × 10²³ per mole, is the number of particles (atoms, molecules or ions) in exactly one mole of any substance. Multiply the amount in moles by this number to get the particle count.
Which formula formats are supported?
Element symbols with subscripts, nested parentheses and brackets such as Ca(OH)2 or K4[Fe(CN)6], and hydrates written with a middle dot like CuSO4·5H2O (a normal period also works).
Related tools
Explore the interactive periodic table for atomic weights and element data, the unit converter for mass and amount units, and the formula solver for rearranging chemistry and physics equations.