Percentage Increase / Decrease Calculator

Enter the starting value in From value and the new one in To value. The calculator works out (to − from) ÷ from × 100 and shows the size of the change as a positive percentage, labelled Increase or Decrease. A second line, Difference, shows the plain gap to − from with its sign.

With the defaults, 80 to 100 is an Increase of 25.00% and a difference of 20. If both values are the same, you'll see an increase of 0.00%.

The percentage is always measured against the starting value, so the same gap gives a different percentage depending on direction:

This is why a 10% fall needs an 11.11% rise to recover. It also explains why gaining 50% and then losing 50% leaves you behind: 100 becomes 150, then 75, a 25% decrease overall.

If your conversion rate went from 2.5% to 3%, enter 2.5 and 3. The result is an Increase of 20.00%, and the Difference line shows 0.5. That 0.5 is the change in percentage points.

Both are correct, and they answer different questions. "Up half a point" describes the rate. "Up 20%" describes how much better it got relative to where it started. Say which one you mean when you report it, since a 20% rise sounds far bigger than half a point.

The calculator gives the total change between two values, not a yearly rate. If something grew from 100 to 150 over five years, the total is a 50% increase, but that is not 10% a year. Because growth compounds, the steady yearly rate is ((to ÷ from)^(1 ÷ years) − 1) × 100, which here is 8.45%.

Going the other way, successive changes multiply rather than add. Two 10% increases take 100 to 121, which the calculator confirms is a 21.00% increase in total.

• From 0: any change from zero is undefined as a percentage, so the result shows a dash. Report the Difference instead, such as "up 40 from zero".
• Falling to zero is a 100.00% decrease, and falling below zero goes past 100%. A profit of 40 that turns into a loss of 10 shows as a 125.00% decrease.
• A negative starting value flips the label. From −50 to −25 is shown as a 50.00% decrease, even though the value rose by 25, as the Difference line shows. The usual fix is to divide by the size of the starting value without its sign, which makes it a 50% improvement. When the start is negative, trust the Difference line for direction.