((v2 - v1) / v1)*100 your percent change. v1 is the original value, and v2 is the value it changed to.
The percent error is used in many scientific applications. In labs, it measures how
accurate an experiment is, compared to the expected (often numerical) outcome.
Calculating percentage change and expressing an increase or decrease. ( ΔV / |V1| ) * 100 = ((V2 - V1) / |V1|) * 100 = percentage change.