Moles to Grams Calculator

At a glance:Moles-to-grams is the most basic and most common conversion in chemistry: turning the 'amount of substance in moles (mol)' into 'mass in grams (g)'. The bridge is the molar mass M — the mass of one mole of the substance, unit g/mol, numerically equal to its formula mass (sum of atomic or molecular weights). The three quantities relate by m = n·M, where n is the amount (mol), M is the molar mass (g/mol) and m is the mass (g); reversed it is n = m/M (grams to moles), or M = m/n (molar mass from mass and moles). To understand why this conversion is needed, first grasp what a 'mole' means: chemical reactions proceed by 'ratios of particle numbers' (e.g. 2H₂ + O₂ → 2H₂O is 2 hydrogen molecules to 1 oxygen molecule), but a lab balance measures mass, not particle count. The mole is the bridge linking 'microscopic particle count' to 'macroscopic mass': 1 mol of any substance contains Avogadro's constant 6.022×10²³ particles, and the mass of that many particles equals the substance's formula mass in grams (i.e. the molar mass). So as long as you know how many moles you need and the substance's molar mass, you can compute how many grams to weigh. Using this tool's default: take 2 mol of sodium chloride (NaCl), its molar mass M = 22.99 (Na) + 35.45 (Cl) = 58.44 g/mol, so the required mass m = 2 × 58.44 = 116.88 g. Molar masses of common substances: water H₂O = 18.02, sodium chloride NaCl = 58.44, glucose C₆H₁₂O₆ = 180.16, sodium carbonate Na₂CO₃ = 105.99, sodium hydroxide NaOH = 40.00 g/mol; the molar mass is obtained by summing the atomic weights of every atom in the formula (from the periodic table) by count. This conversion has very broad uses: first, when preparing a solution of a specified molar concentration, first compute the required moles from n = C·V, then convert to grams to weigh using m = n·M. Second, in stoichiometric calculations, convert the moles of reactant or product into weighable mass, or reverse — convert the weighed mass into moles to judge the limiting reagent and compute theoretical yield. Third, dilution, titration and standard preparation all rely on this step. Notes: first, the molar mass must be computed from the correct formula; hydrates (e.g. CuSO₄·5H₂O) must include the water of crystallisation. Second, the units of n and m must match M (if M is g/mol, then n is mol and m is g; kg/kmol also works with the same number). Third, this tool assumes you already know the molar mass and computes m from n and M; to reverse from mass to moles use n = m/M. In short, m = n·M is the key step that translates the 'mole language' of stoichiometry into the 'grams' a balance can measure — an essential tool for every chemistry student and lab worker.