Percentage Change Calculator

How it works

Percentage change is a general way to express how much something has changed relative to its starting value. Unlike percentage increase or decrease individually, this calculator handles both directions and clearly labels the result.

The formula

A positive result means the value has increased; a negative result means it has decreased. The sign tells you the direction and the number tells you the magnitude.

Why this works: The formula always expresses the change relative to the starting value, so a £200 rise from £1,000 and a £200 rise from £2,000 produce different percentages (20% and 10% respectively), which correctly reflects their different significance. The sign makes the direction explicit without needing a separate formula.

Difference from percentage increase or decrease

The formula is identical to increase and decrease, but this calculator accepts both directions and labels the result accordingly. If you only need one direction, use the dedicated tool to calculate a percentage rise or the one that finds the percentage that a value has fallen by. For comparing two values without a time reference, the percentage difference calculator treats both values equally.

Worked examples

When to use this

Percentage change is the go-to measure whenever you need to express how much something has moved relative to a starting point. Here are four typical UK situations:

• Monitoring food inflation: The Office for National Statistics tracks grocery price changes month on month. Expressing those shifts as a percentage change makes it easy to compare across product categories and over time.
• Tracking investment fund performance: A SIPP or stocks and shares ISA worth £15,000 that grows to £17,400 has risen by 16%. The percentage change is the standard way fund managers and comparison sites present returns.
• Reporting business KPIs: A monthly website traffic report showing 8,400 sessions up from 7,000 last month shows a 20% increase. Percentage change makes these figures comparable across months with different baselines.
• Comparing school performance: A school whose GCSE pass rate moved from 68% to 74% year on year has improved by 8.8%. Quoting the percentage change avoids ambiguity about whether you mean percentage points or relative improvement.

Understanding the result

A positive percentage change means the value has grown relative to the starting point. A negative percentage change means it has fallen. Zero means no change. The magnitude tells you how significant the change is as a proportion of the original.

One important asymmetry: if a value rises by 50% and then falls by 50%, you do not return to the original. After a 50% rise from 100 you have 150, and 50% of 150 is 75, leaving you at 75 rather than 100. The percentage change in each step uses a different base, which is why sequential percentage changes cannot simply be added or subtracted.

Related concepts

➡ When you need to express the arithmetic gap between two rates (such as comparing two interest rates) rather than how one changed from the other, you can find the difference between two percentages expressed in percentage points. ➡ To find what a value was before a change was applied, the reverse percentage calculator undoes the change to reveal the original figure. ➡ If you want to know the absolute pound amount the percentage change represents, the percentage of a number calculator converts any rate into a real-world amount.

How to do this in Excel

Put the old value in A1 and the new value in B1. Using ABS() around the denominator ensures the formula handles negative starting values correctly, which matters when tracking items such as a loss that has reduced. For positive values only, you can simplify to =(B1-A1)/A1*100.

How to do this without a calculator

Subtract the old value from the new to get the change. Then divide the change by the old value and multiply by 100. For quick mental maths, round the original to the nearest convenient number first. If a bill went from £95 to £114, round to £100 and see that the change (£19) is close to 20% of £100, so the answer is roughly 20%. The exact answer is 20%, which confirms the estimate.

Common mistakes

Related calculators