Enthalpy, entropy, Gibbs energy, and reaction energy calculators. Browse our free thermochemistry tools below — all calculators are instant, accurate, and require no sign-up.
Activation Energy Calculator — Calculate activation energy using the Arrhenius equation with two-temperature rate data. Supports Ea from rate constants, frequency factor estimation, and temperature dependence analysis.
Arrhenius Equation Calculator — Solve the Arrhenius equation for rate constant, activation energy, frequency factor, or temperature. Includes Arrhenius plot data and multi-temperature analysis.
Combustion Analysis Calculator — Determine empirical and molecular formulas from combustion analysis data. Enter masses of CO₂ and H₂O produced to find percent composition and molecular formula.
Combustion Reaction Calculator — Calculate heat released, oxygen required, and products formed in combustion reactions. Supports hydrocarbons, alcohols, and custom organic fuels with complete/incomplete combustion.
Entropy Calculator — Calculate entropy change for chemical reactions, phase transitions, and mixing processes. Covers ΔS°rxn from standard molar entropies and Boltzmann entropy.
Equilibrium Constant Calculator — Calculate equilibrium constant Kc, Kp, and reaction quotient Q. Determine equilibrium concentrations, predict reaction direction, and convert between Kc and Kp.
Gibbs Free Energy Calculator — Calculate Gibbs free energy (ΔG) from enthalpy and entropy, determine spontaneity, and find equilibrium temperatures. Supports ΔG°rxn from formation data and ΔG = ΔH - TΔS.
Heat of Combustion Calculator — Calculate standard enthalpy of combustion for fuels and organic compounds. Compare higher and lower heating values, energy density, and CO₂ intensity across fuels.
Rate Constant Calculator — Calculate reaction rate constants from experimental data for zero, first, and second order reactions. Determine reaction order, half-life, and rate law parameters.