MultiConvers

Percentage Change Calculator

Measure how far a figure moved from its own starting point — a price, a headcount, a score — not “what percent is the new number of the old one.”

Updated

How to use

  1. Enter the original value (last year’s rent, last quarter’s users, the old price).
  2. Enter the new value after the change.
  3. Read the signed percent. Positive is an increase; negative is a decrease.
  4. Use the percentage calculator if you instead know a part and a whole, and Discount if you already know the percent off.

How it works

Percentage change asks how far you travelled relative to where you started. From 80 to 60 the drop is 20, and 20 is 25% of the original 80. 60 is still 75% of 80 — that second sentence is a static ratio, not a change, and belongs on the ordinary percentage page.

A raise from 40,000 to 44,000 is ((44,000 − 40,000) ÷ 40,000) × 100 = 10%. People often divide by the new number instead and report 9.09%, which understates the raise. The denominator is always the original.

The absolute value on the original amount is there for signed starting points. A reading from −50 to −40 became less negative: the change is +10 on a base of 50, so +20%. From −20 to −30 is a 50% decrease. Without the absolute value those signs flip in confusing ways.

Zero as a start is a hard stop. You cannot say a figure “grew 100% from nothing” as a finite percent; the formula would divide by zero. If both values are zero the change is 0%.

This is not a discount tool. “20% off 80” is a planned markdown. “80 became 64” is a measured change that happens to equal 20% off. Use Discount when you already know the percent; use this page when you have two observed totals.

Formula

Percentage change = ((new − old) ÷ |old|) × 100

Worked examples

  • 50 to 75

    old 50, new 75 → 50% increase

  • 80 to 60

    old 80, new 60 → 25% decrease

Useful notes

  • Always divide by the original value, not the new one.
  • A 0% result means the two values are equal.
  • Growth from 0 to a non-zero value is undefined here.

FAQ

How do I calculate percentage increase?

Subtract the original value from the new value, divide by the absolute original value, and multiply by 100. From 50 to 75 that is ((75 − 50) ÷ 50) × 100 = 50%.

What if the original value is zero?

If both values are zero, the change is 0%. If the original is zero and the new value is not, percentage change is undefined because the formula would divide by zero.

Is percentage change the same as “what percent is X of Y”?

No. “10 is what percent of 50” is a static ratio (20%). Percentage change asks how far you moved from the starting number.

Why is an increase from 50 to 100 called 100%, not 200%?

You added 50 onto a base of 50, which is 100% of the start. 200% would mean the new value is 150 (the start plus twice the start).

Can I use this for a percent-off sale?

Only after you already have both prices. If you know the percent and the list price, the discount calculator is the direct tool.

Guides

Related tools

See all Math tools.