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Old value to new value

Percent Change Calculator

Percentage increase or decrease from an original value to a new value. A zero baseline is not defined.

Your numbers

Percent change

How much a value rose or fell from an original baseline.

Percent change

25%increase
How we got this
  1. Original80
  2. New100
  3. Percent change(new − original) ÷ |original| × 10025%
What we assumed
  • Percent change uses the absolute value of the original number in the denominator.
  • A zero original value is not a defined percent change.
Technical details

Method percent-change-v1.0.0Data Manual inputs / fixed rules

Guide

Increase or decrease from an original value

CostAnswer editorialIndependent calculator publisher

Percent change is (new − original) / original. A zero original is undefined and rejected. This is not inflation (use CPI-U) and not a log return.

Up 50% then down 50% is not back to start

100 increased by 50% is 150. 150 decreased by 50% is 75. Sequential percent changes do not cancel. Run each step separately if you need a chain.

Questions about this calculator

How do I calculate a percentage increase?

Enter the original and the new value. The sign shows increase versus decrease. Zero as a baseline is not defined.

Terms used here

Baseline
The original value in the denominator. It cannot be zero on this page.

Practical tips

  • For buying power across years, use the inflation calculator, not a homemade percent on two prices of different goods.

Limits and caveats

  • Exact for two numbers. Not a market return with dividends.

Results are for information. They are not legal, tax, medical, or financial advice. How the math is maintained · Report a wrong figure.

Engine notes

Rounding, versioning, and omissions that sit beside the guide rather than repeating it.

  • Formula. ((new − old) ÷ |old|) × 100. From 80 to 100 that is a 25% increase.
  • Zero original. When the original value is zero, percent change is not defined. The calculator says so instead of inventing a number.
  • Not the Percentage Calculator. “What is 15% of 200?” is a different intent and stays on the Percentage page.

Calculation receipt

What each number here is

This answer is arithmetic on what you enter. No outside dataset is involved, so nothing here can go out of date.

Percentage change is (new − old) ÷ old.

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