Entropy Change Calculator

About this calculator

This calculator finds the entropy change of an isothermal, reversible process using ΔS = Q/T, where Q is the heat transferred and T is the absolute temperature (in kelvin) at which the transfer happens. Entropy is the thermodynamic measure of disorder or the number of microscopic ways energy can be arranged, and the second law of thermodynamics states that the total entropy of an isolated system never decreases.

Chemists and physicists use this formula to analyze phase changes like melting and boiling (where heat is absorbed or released at a constant temperature), to evaluate the efficiency limits of heat engines and refrigeration cycles, and to determine whether a process is thermodynamically favorable. Chemistry and physics students, thermodynamics researchers, and mechanical and chemical engineers designing engines or industrial processes use it to quantify how much a system's disorder increases or decreases.