Percentage Change Calculator

Most people use "percentage change" and "percentage difference" as if they mean the same thing. They do not. One is directional, tracking how a value moved from a starting point to an ending point. The other is symmetrical, measuring the gap between two values when neither counts as the "original." Using the wrong formula gives the wrong answer. This calculator handles both.

Use this when comparing before and after — one number came first.

The original value

The value after the change

How to use this calculator

1
Percentage change: choose this mode when one number came before the other in time. Enter the original value in From and the later value in To. A positive result is an increase; a negative result is a decrease.
2
Percentage difference: choose this mode when comparing two values that exist at the same point in time and neither is the "original." Enter the two values in Value A and Value B. The result is always positive.

Still unsure? Ask: "Did one of these numbers come first?" If yes, use percentage change. If both numbers exist at the same point in time, use percentage difference.

Formula

Percentage change (directional):

% change = ((To − From) ÷ From) × 100

Positive = increase · Negative = decrease

Percentage difference (non-directional):

% difference = (|A − B| ÷ ((A + B) ÷ 2)) × 100

Always positive · Same result regardless of order

Worked examples

Percentage change examples

Sales revenue: Q1 £84,000 → Q2 £97,000

((97,000 − 84,000) ÷ 84,000) × 100 = +15.48%

Student score: mock 54 → final 71

((71 − 54) ÷ 54) × 100 = +31.48%

Percentage difference examples

Trainers: £89 at one retailer vs £115 at another

|89 − 115| ÷ ((89 + 115) ÷ 2) × 100 = 25.49%

Job offers: £38,000 vs £44,500

|38,000 − 44,500| ÷ ((38,000 + 44,500) ÷ 2) × 100 = 15.76%

How it works

Take two numbers: 60 and 90. Run them through both formulas and the difference becomes clear.

Percentage change (60 as original):

(90 − 60) ÷ 60 × 100 = 50%

Percentage difference:

|90 − 60| ÷ ((90 + 60) ÷ 2) × 100 = 40%

Same two numbers, two different answers: 50% and 40%. Neither is wrong. They answer different questions. Percentage change says "90 is 50% more than 60." Percentage difference says "60 and 90 are 40% apart from each other, measured against their midpoint."

This matters in practice because using the wrong formula gives a misleading result. News reports and business presentations sometimes mix them up, producing a number that sounds plausible but describes the wrong thing.

Common uses

  • Quarterly or annual revenue comparison: track whether a business grew or shrank from one period to the next (percentage change)
  • Exam and test score improvement: see how much a student's performance moved between two sittings (percentage change)
  • Price comparison shopping: measure the gap between two products or retailers when neither price is the "original" (percentage difference)
  • Population growth: compare a city or country's population between two census years (percentage change)
  • Salary negotiation: quantify the gap between a current salary and a new offer, or between two competing offers (percentage difference)
  • Energy bill increases: calculate how much your electricity or gas bill has risen year on year (percentage change)
  • Investment portfolio tracking: measure the percentage change in the value of a portfolio over a set period (percentage change)
  • Comparing regional statistics: assess the gap between unemployment rates or average wages across two regions where neither is the baseline (percentage difference)

Frequently asked questions

Percentage change measures how a value moved from one point to another, with a clear starting value as the reference. It can be positive (an increase) or negative (a decrease). Percentage difference measures the gap between two values when neither is the starting point, using their average as the reference. It is always positive. Using the wrong one for a given situation gives a misleading result.

Subtract the old value from the new value, then divide by the old value, then multiply by 100. Written out: ((New − Old) ÷ Old) × 100. For example, a value rising from 200 to 250 gives ((250 − 200) ÷ 200) × 100 = 25%. A positive result means an increase; a negative result means a decrease.

Because neither of the two values is the "original" or reference point. If you used one of them as the denominator, the result would change depending on which one you chose. Using the average treats both values equally and produces a symmetrical result: the percentage difference between A and B is the same as between B and A.

Yes. A negative percentage change simply means the value fell. If a value dropped from 500 to 400, the percentage change is ((400 − 500) ÷ 500) × 100 = −20%. Percentage difference, by contrast, is always positive because it uses an absolute value and measures a gap rather than a direction.

No, and this catches many people out. A value rising by 50% and then falling by 50% does not return to where it started. If you start at 100, a 50% increase takes you to 150. A subsequent 50% decrease takes you to 75, not 100. The reason is that the 50% fall applies to the new, higher value of 150, not the original 100. To return from 150 to 100 requires a decrease of only 33.3%, not 50%.

Related calculators

Percentage Increase Calculator → Find the percentage by which a value has risen, with the full formula shown. Percentage Decrease Calculator → Calculate by how much a value has fallen, including the recovery paradox explained. CAGR Calculator → Find the compound annual growth rate when a value changes over multiple years.

Last reviewed: May 2026