ChemCalc
Molarity, dilution, pH, stoichiometry, and reaction yield. Fast answers for the lab bench or the homework set.
Molarity Calculator
Calculate molarity from mass, molar mass, and volume. Or find any missing variable.
Dilution Calculator (C1V1 = C2V2)
Calculate dilution volumes using the C1V1 = C2V2 equation.
pH Calculator
Convert between pH, pOH, [H⁺], and [OH⁻]. Enter any one to find the rest.
Stoichiometry Calculator
Convert between moles, grams, and molecules using molar mass and Avogadro’s number.
Reaction Yield Calculator
Calculate theoretical yield, actual yield, and percent yield for chemical reactions.
About ChemCalc
ChemCalc provides free chemistry calculators for students, lab technicians, and researchers. Molarity, dilution, pH, stoichiometry, and reaction yield — all running in your browser with no data leaving your device.
Bookmark calculations or share them via URL. Every result includes the formula used so you can verify the math.
Molarity and concentration: molarity (M) = moles of solute / liters of solution. Moles = mass (grams) / molecular weight (g/mol). To make 500 mL of 0.5 M NaCl: moles needed = 0.5 M × 0.5 L = 0.25 mol. Mass = 0.25 mol × 58.44 g/mol = 14.61 g NaCl dissolved and diluted to 500 mL total volume. Dissolving in water then adding more water to reach total volume is critical — not adding a fixed volume of water to the solute.
Dilution: C₁V₁ = C₂V₂ (concentration × volume is conserved). To dilute 10 mL of 5 M HCl to 0.1 M: V₂ = C₁V₁/C₂ = (5 × 10)/0.1 = 500 mL final volume. Add 490 mL of water to 10 mL of stock (always add acid to water, not water to acid, to dissipate heat safely).
pH and pOH: pH = −log₁₀[H⁺]. A solution with [H⁺] = 10⁻³ M has pH 3. pH + pOH = 14 at 25°C (the pKw of water). A pH 3 solution has pOH = 11 and [OH⁻] = 10⁻¹¹ M. Strong acids (HCl, H₂SO₄, HNO₃, HBr, HI, HClO₄) dissociate 100% — pH = −log(concentration). Weak acids use the Ka equilibrium expression: [H⁺] = √(Ka × C) for a simple monoprotic weak acid at typical dilutions.
Stoichiometry: balanced equations give mole ratios. 2H₂ + O₂ → 2H₂O: 2 moles H₂ react with 1 mole O₂ to produce 2 moles H₂O. Limiting reagent is the reactant that runs out first. To find it: convert both reactants to moles of product; whichever yields less product is the limiting reagent. Theoretical yield = moles of limiting reagent × stoichiometric ratio × molecular weight of product.