Your bedroom drifts toward mess on its own, and physics has a name for that drift: entropy. In thermodynamics, entropy measures disorder — and for a reversible heat transfer, the change is simply the heat energy divided by the absolute temperature: ΔS = Q / T. Add heat at high temperature and entropy barely budges; dump the same heat into something cold and entropy jumps.

The second law of thermodynamics says the universe's total entropy never decreases, which is why heat flows from hot to cold and never the reverse on its own. Your refrigerator fights this law around the clock, spending electrical work to pump heat from the cold interior to the warm kitchen — and the entropy math sets the minimum energy that fight must cost. Power plants live by the same accounting: the bigger the temperature gap between boiler and cooling tower, the more useful work each joule of heat can do.

This calculator performs the entropy division's core step. Type the heat energy in joules in the Variable A box and the reciprocal of the absolute temperature (1/T, using kelvin) in the Variable B box. The Result box gives the entropy change in joules per kelvin — the disorder price tag of that heat transfer.

With the pre-filled defaults — Variable A 10, Variable B 5 — the Entropy Calculator returns Result 50.0000. Change any input and those results update instantly, so you can see exactly how each number you enter moves the answer.