Molarity Calculator - g/mL to Molarity, g/L to Molarity and Grams to Moles
Convert g/mL, g/L or grams to molarity (M). Calculate moles, millimoles and concentration from mass, molar mass and volume.
Molarity (M) is the number of moles of solute per liter of solution - the most common concentration unit in chemistry. This calculator handles every common workflow: converting g/mL to molarity (density × 1000 / molar mass), g/L to molarity (concentration / molar mass), mg/mL to molarity (divide by molar mass) and grams to moles (mass / molar mass). The general formula is M = (mass in g / molar mass in g/mol) / volume in L. Quick reference for concentrated reagent stock solutions: 37% HCl at 1.19 g/mL ≈ 12.1 M, 98% H2SO4 at 1.84 g/mL ≈ 18.4 M, 65% HNO3 at 1.40 g/mL ≈ 14.4 M, 25% ammonia at 0.91 g/mL ≈ 13.4 M. For pure liquids: water (1.00 g/mL, 18.02 g/mol) = 55.5 M, ethanol (0.789 g/mL, 46.07 g/mol) = 17.1 M.
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Frequently asked questions
Multiply density (g/mL) by 1000 to get g/L, then divide by molar mass in g/mol. Formula: M = (density × 1000 × purity) / molar mass. Examples: pure water (1.00 g/mL, 18.02 g/mol) = 1000 / 18.02 = 55.5 M. Pure H2SO4 (1.84 g/mL, 98.08 g/mol) = 1840 / 98.08 = 18.76 M. For 98% concentrated H2SO4, multiply by 0.98 to get 18.4 M. For 37% HCl (1.19 g/mL, 36.46 g/mol), the answer is 1190 × 0.37 / 36.46 = 12.1 M.
Divide g/L by molar mass to get M directly. Example: 40 g/L of NaOH (molar mass 40 g/mol) = 1 M. 58.44 g/L of NaCl = 1 M. For mg/mL the value is numerically identical to g/L (1 mg/mL = 1 g/L), so use the same formula. The units g/L cancel with g/mol to leave mol/L = M.
For volume: V (mL) = (moles × 1000) / molarity. To get 0.05 mol from a 0.5 M solution, you need 0.05 / 0.5 = 0.1 L = 100 mL. For mass: grams = molarity × volume (L) × molar mass. To make 250 mL of 1 M NaCl: 1 × 0.25 × 58.44 = 14.61 g of NaCl in 250 mL water.
Dissolve one molar mass in 1 L for 1 M, then dilute with C1V1 = C2V2. NaCl (58.44 g/mol): 58.44 g/L = 1 M, 5.844 g/L = 0.1 M, 0.584 g/L = 0.01 M. NaOH (40 g/mol): 40 g/L = 1 M. Glucose (180.16 g/mol): 180.16 g/L = 1 M. KCl (74.55 g/mol): 74.55 g/L = 1 M. Always add the solid to a partially filled volumetric flask, dissolve, then fill to the mark.
Molarity (M) is moles of solute per liter of solution - temperature-dependent because volumes expand. Molality (m) is moles per kilogram of solvent - temperature-independent, used for colligative properties (freezing point, boiling point). Normality (N) is equivalents per liter - used in acid-base titrations. For HCl, N = M; for H2SO4, N = 2M because it donates two protons.