MATH · PERCENTAGE CHANGE
Percentage Change Calculator
Calculate the percentage increase or decrease between two values. Handles positive, negative, and zero-result cases with clear directional output.
About This Calculator
Find out how much something changed — as a percentage. Enter a starting value and an ending value and this calculator tells you the percentage increase or decrease, the direction (increase or decrease), and an interpretation line you can read at a glance.
How It Works
The formula is ((new − old) / old) × 100. A positive result is an increase; a negative result is a decrease. The calculator guards against the edge case where the old value is zero — division by zero is undefined, so the calculator returns an error instead of an incorrect or infinite result.
The Formula
% Change = ((New − Old) / Old) × 100
- New
- the ending or final value
- Old
- the starting or original value (cannot be zero)
Frequently Asked Questions
- What is the difference between this and the Percentage Calculator?
- The existing Percentage Calculator covers three modes — X% of Y, % change, and % difference. This calculator is the dedicated, higher-traffic version of % change only — ((new−old)/old)×100 — with a cleaner interface and signed output. If you need X% of a number or the symmetric % difference, use the Percentage Calculator instead.
- Why does percentage change return an error when the old value is zero?
- The formula divides by the old value. Dividing by zero is mathematically undefined — there is no percentage change from zero, only an absolute change. The calculator surfaces this as an error rather than returning infinity or NaN.
- Can old and new values be negative?
- Yes. The formula works for any real numbers except old=0. However, be aware that when the old value is negative, the sign of the result can be counterintuitive — the formula still divides by a negative denominator.
- What is the formula for percentage increase vs. percentage decrease?
- There is only one formula for both — ((new−old)/old)×100. A positive result is an increase; a negative result is a decrease. The calculator labels the direction explicitly so you do not have to interpret the sign yourself.