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Percentage Change Calculator

Two figures, one before and one after: this works out how far it moved as a percentage, in which direction, and against which number. That last part is where most percentage-change sums go wrong.

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The earlier figure. Everything is measured against this one.

The later figure.

Loaded with an example. Type over either field.

Answer

20%

From 150 to 180 is a 20% increase — up ↑

From
150
To
180
The increase
+30

What each figure is

A percentage means nothing on its own. These are the numbers it is made of.

  • FromYou entered thisthe starting figure — everything is measured against this150
  • ToYou entered thisthe figure you ended up with180
  • The increasethe gap between the two, in plain units+30

How that was worked out

Each step, and why it is that step.

  1. Step 1 — Find the gap

    180 − 150 = 30

    How far it moved, before turning that into a percentage of anything.

  2. Step 2 — Divide by where you started

    30 ÷ 150 = 0.2

    Percentage change is always a share of the ORIGINAL figure. This is the step people get wrong.

  3. Step 3 — Scale it to a hundred

    0.2 × 100 = 20%

    Same last step as every other percentage question.

Check it backwards: 150 × 1.2 = 180 — the figure you ended on

The mistake this prevents

Dividing by 180 instead of 150 gives 16.67%, which is a different question — that is what 30 is as a share of where you finished, not of where you began.

Check this before you rely on it. A free everyday calculator, provided as a guide — not tax, accounting, financial or legal advice. The working is shown above so you can verify it against your own figures. See our terms of use.

How it works

STEP 1

Enter the earlier figure

Last year’s revenue, the old price, the reading you took first. This is the number everything is measured against, and putting the wrong figure here is what produces a wrong answer that looks plausible.

STEP 2

Enter the later figure

Where it ended up. Higher gives an increase, lower gives a decrease, and the direction is stated in words as well as a sign.

STEP 3

Check which number it divided by

The working shows the division explicitly, and the page also shows what you would have got by dividing by the finishing figure instead — a different question, and the usual error.

The guideHow to calculate percentages — the five sums people actually needTo find P% of a number, multiply by P ÷ 100. To find what one number is as a percentage of another, divide the part by the whole and multiply by 100.Read it

Common questions

What is the percentage change formula?

(new − old) ÷ old × 100. From 150 to 180 that is 30 ÷ 150 × 100 = a 20% increase. The division is by the OLD figure, always — dividing by 180 instead gives 16.67%, which answers "what is the gap as a share of where I finished".

Is percentage change the same as percentage difference?

No. Change has a direction and is measured against the starting figure; difference is symmetric and measured against the midpoint of the two. 150 and 180 are a 20% change but an 18.18% difference. If swapping your two numbers ought to leave the answer alone, you want the difference calculator.

How do I work out year-on-year change?

Put last year in the first field and this year in the second. For several years running, compare each year with the one before it rather than with the first year — otherwise you are measuring cumulative growth, which is a compound-interest question.

What if the starting figure is zero?

There is no answer. Any increase from zero is infinitely large as a percentage, so the calculator says so rather than printing a misleading number. Quote the absolute change instead — "up by 40" rather than "up by 4,000%".

Is a percentage point the same as a percent?

No. A rate moving from 4% to 5% has risen by one percentage point, but that is a 25% increase. Newspapers mix these up constantly. Use this calculator for the percentage and plain subtraction for the points.

Can it handle negative numbers?

Yes. The division is by the magnitude of the starting figure, so going from −50 to −25 reads as a 50% improvement rather than a −50% one.

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