# Grams to Moles Calculator URL: https://speedycalculator.com/calculators/chemistry/grams-to-moles/ Last updated: 2026-10-30 > The grams to moles calculator converts a mass in grams into an amount in moles using the molar mass of the substance – and back again – or finds the molar mass from a known mass and number of moles. It also gives the number of particles and the mass of one particle. ## Inputs - Find - Substance - Molar mass (g/mol, kg/mol, Da (u), kDa) - Mass (g, mg, µg, kg, oz, lb) - Amount of substance (mol, mmol, µmol, nmol, kmol) ## Results - Molar mass used - Molar mass used - Amount of substance (moles) - Mass - Number of particles (molecules or formula units) - Mass of one particle - Mass of one particle in daltons ## Formula ``` n = m ÷ M · m = n × M · M = m ÷ n · number of particles N = n × N_A (N_A = 6.02214076 × 10²³ mol⁻¹) ``` ## Explanation Chemists count atoms and molecules in moles, but balances measure grams. The bridge between the two is the molar mass M – the mass of one mole of a substance in grams per mole, numerically equal to the formula mass in daltons. Water has M = 18.015 g/mol, so 18.015 g of water is one mole, or 6.022 × 10²³ molecules. Converting grams to moles is the first step of almost every stoichiometry problem: balanced equations give ratios of moles, not grams, so you convert the masses you weigh into moles, apply the mole ratio and convert back. The same relationship, n = m/M, is also used in reverse – to find how many grams to weigh out for a given number of moles – and to identify an unknown compound from a measured mass and amount. Choose a common substance to fill in its molar mass, or type the molar mass of your own compound (add up the atomic masses in its formula, including any water of crystallisation). ### How to use the Grams to Moles Calculator - **Find** - **Substance** - **Molar mass** - **Mass** - **Amount of substance** Results update as you type, every field has its own unit menu, and everything is calculated in your browser. ### How it works Choose what to find. For moles, divide the mass by the molar mass; for mass, multiply moles by the molar mass; for molar mass, divide the mass by the moles. The number of particles is the amount in moles multiplied by the Avogadro constant, and the mass of a single particle is M ÷ N_A. ### Worked example How many moles are in 25 g of table salt? NaCl has M = 22.990 + 35.45 = 58.44 g/mol, so n = 25 ÷ 58.44 = 0.4278 mol. That is 0.4278 × 6.022 × 10²³ = 2.576 × 10²³ formula units, and one NaCl unit weighs 58.44 ÷ 6.022 × 10²³ = 9.70 × 10⁻²³ g. Going the other way, 0.5 mol of glucose (180.156 g/mol) weighs 0.5 × 180.156 = 90.08 g. ### Molar masses of common substances SubstanceFormulaMolar mass (g/mol)1 g equalsWaterH₂O18.0150.05551 molSodium chlorideNaCl58.440.01711 molCarbon dioxideCO₂44.0090.02272 molGlucoseC₆H₁₂O₆180.1560.005551 molSulfuric acidH₂SO₄98.0720.01020 molCalcium carbonateCaCO₃100.0860.009991 mol ### Tips - Always start from a balanced equation – coefficients give the mole ratio. - Convert everything to moles first, then use the ratio, then convert back. - Every field has its own unit menu – g, mg, mol, mmol, L and mL all work. - Everything is calculated in your browser. ### Common mistakes to avoid - Using mass ratios instead of mole ratios. - Forgetting water of crystallisation in the molar mass of hydrates. - Confusing molarity (per litre of solution) with molality (per kilogram of solvent). ### Inputs explained FieldWhat to enterFindChoose one: Moles (from grams), Grams (from moles), Molar mass (from grams and moles)SubstanceChoose one: Water H₂O – 18.015, Sodium chloride NaCl – 58.44, Glucose C₆H₁₂O₆ – 180.156, Sucrose C₁₂H₂₂O₁₁ – 342.297 …Molar massUnits: g/mol, kg/mol, Da (u), kDaMassUnits: g, mg, µg, kg, oz, lbAmount of substanceUnits: mol, mmol, µmol, nmol, kmol ### What each result means - **Mass of one particle** = [Molar mass used]÷6.02214076e+23 - **Mass of one particle in daltons** = [Molar mass used] ## Worked example Inputs — Find: Moles (from grams); Substance: Sodium chloride NaCl – 58.44; Mass: 25 g. Results — Molar mass used = 58.44 g/mol; **Amount of substance (moles) = 0.427789 mol**; Number of particles (molecules or formula units) = 2.5762e23; Mass of one particle = 9.7042e-23 g; Mass of one particle in daltons = 58.44 Da. ## Key terms - **Mole**: Amount of substance containing exactly 6.02214076 × 10²³ specified particles. - **Molar mass**: Mass of one mole of a substance, in g/mol. - **Avogadro constant**: N_A = 6.02214076 × 10²³ mol⁻¹, the number of particles per mole (exact since 2019). - **Formula unit**: The smallest repeating unit of an ionic compound, such as one NaCl. ## FAQ **How do I convert grams to moles?** Divide the mass by the molar mass: n = m ÷ M. For example, 100 g of water ÷ 18.015 g/mol = 5.551 mol. **How do I convert moles to grams?** Multiply by the molar mass: m = n × M. Half a mole of NaCl is 0.5 × 58.44 = 29.22 g. **Where do I find the molar mass?** Add up the standard atomic weights of every atom in the formula (e.g. H₂SO₄ = 2 × 1.008 + 32.06 + 4 × 15.999 = 98.07 g/mol) or read it from the reagent bottle. **How many molecules are in 1 gram of water?** 1 ÷ 18.015 = 0.05551 mol, times 6.022 × 10²³ = 3.34 × 10²² molecules. **What about hydrates?** Include the water of crystallisation: CuSO₄·5H₂O has M = 249.68 g/mol, not 159.60 g/mol for anhydrous CuSO₄. **Is molar mass the same as molecular weight?** Numerically yes – the molar mass in g/mol equals the relative molecular mass (molecular weight) – but molar mass has units, molecular weight is dimensionless. **How do I convert grams of a gas to litres?** First convert to moles, then use the molar volume: about 22.71 L/mol at 0 °C and 1 bar, or 24.47 L/mol at 25 °C and 1 atm. **What formula does the Grams to Moles Calculator use?** n = m ÷ M · m = n × M · M = m ÷ n · number of particles N = n × N_A (N_A = 6.02214076 × 10²³ mol⁻¹). ## Sources - [IUPAC Compendium of Chemical Terminology (Gold Book)](https://goldbook.iupac.org/) - [IUPAC Commission on Isotopic Abundances and Atomic Weights – Standard atomic weights](https://www.ciaaw.org/atomic-weights.htm) - [NIST – Fundamental physical constants (CODATA)](https://physics.nist.gov/cuu/Constants/)