How percent change is computed here

The percentage calculator has a percent-change mode that uses one formula: ((new value − old value) ÷ old value) × 100. That is the same arithmetic people use when a price, a score, or a count moves from one number to another.

Take a price that moves from 80 to 92. The difference is 12. Divide 12 by the old value of 80, then multiply by 100. The result is 15 percent. You can open the percentage calculator, choose percent change, and enter 80 then 92 to see that 15% on the readout.

The old value is the denominator. If the old value is 0, the division is undefined. The calculator reports that next to the field instead of showing Infinity. A drop uses the same formula and produces a negative percent. A move from 100 to 80 is ((80 − 100) ÷ 100) × 100 = −20 percent.

Percent change is not the same as “A is what percent of B.” Twelve is 15 percent of 80, and that uses (part ÷ whole) × 100. That second formula does not care which number came first in time. Percent change does, because it always divides by the old value.

This guide does not compute a loan payoff or a paycheck change. Those belong on other kinds of tools. For a percent of a known amount, stay on the first mode of the percentage calculator: (percent ÷ 100) × amount.