About Percentage Change
Percentage Change measures the movement between two values and reports both the magnitude and the direction. It subtracts the starting value from the ending value, divides by the size of the starting value, and multiplies by 100 — so 100 rising to 125 is reported as a 25.00% increase.
Dividing by the absolute value of the start, rather than the signed value, is a small decision with a visible consequence: going from -100 to -50 is reported as a 50% increase rather than a decrease. That is the interpretation most people want when they track a metric that happens to be negative, such as a temperature anomaly or a net cash position.
One case deserves a warning rather than a number. When the starting value is zero, percentage change is mathematically undefined — there is no finite rate that describes going from nothing to something. The tool returns 0.00% increase in that situation, which is a guard against a division error rather than a claim about your data.
What it will not do is chain or compound. A sequence of movements cannot be entered at once to get an overall change, and no cumulative figure is produced — which is worth noting because consecutive percentage changes do not simply add up, so summing them by hand gives the wrong answer. The result carries no intermediate working: the difference and the ratio are not shown, so checking the arithmetic means recomputing it elsewhere. There is also no period label, no annualised or per-month variant, and no way to reverse the calculation and recover a starting value from an ending value and a rate. Because the divisor is the absolute value of the start, a movement that crosses zero is reported in a way that a strictly signed calculation would not reproduce.
How to use Percentage Change
- 1 Enter the starting value in the From field.
- 2 Enter the ending value in the To field.
- 3 Read the result: a signed percentage plus the word increase or decrease.
Frequently asked questions
Why does going from -100 to -50 count as an increase?
Because the divisor is the absolute value of the starting point. The signed approach would label that same movement a decrease, which contradicts how people read a negative metric moving toward zero. The magnitude is identical either way; only the label changes.
What happens if the starting value is zero?
It reports 0.00% increase. The true answer is undefined, because no finite percentage describes growth from zero. Treat a zero starting point as a signal that percentage change is the wrong metric for that comparison.
How many decimal places does the result carry?
Two. That is enough for reporting and avoids implying more precision than two rounded inputs can support. If you need the raw ratio, divide the two values directly.
Can I use it for a percentage decrease?
Yes — just put the larger value in From. The sign and the direction word are both derived from the arithmetic, so 200 falling to 150 comes back as 25.00% decrease.
Free, online, and private
Free to use
Percentage Change is completely free. There is no account to create, no login, and no hidden charge or usage limit.
Runs online in your browser
It is a free online tool that runs entirely in your browser. Nothing to download or install — open the page and start using it right away.
Your data stays private
All processing happens locally on your device. Your input is never uploaded, stored, or tracked, so it never leaves your browser.
How Percentage Change behaves in detail
These are the specifics of this implementation — the exact ranges, defaults and fixed settings you are working with.
| Parameter | Value |
|---|---|
| Formula | (to − from) ÷ |from| × 100 |
| Direction label | "increase" or "decrease" appended to the figure, chosen by whether the signed change is at or above zero |
| Zero baseline | from = 0 short-circuits the division and reports a change of 0, printed as "0.00% increase" |
| Absolute denominator | the magnitude of the starting value is used, so a negative baseline still yields the expected direction |
| Precision | 2 decimal places |
| Defaults | from 100 to 125, which returns 25.00% increase |
Compiled from the implementation of this tool and checked against it by itoolnet.
What Percentage Change does not do
Knowing the edges of a tool saves more time than another list of its features. These are the cases where it will not do what you might expect.
- A starting value of zero is answered with a flat 0.00% increase because the divide-by-zero is short-circuited rather than reported. Going from 0 to 500 is not a 0% move under any definition, and 0 to 0 comes back looking like a real measured change.
- The denominator is the absolute starting value rather than the midpoint of the two, so a rise from A to B is not the mirror image of the fall from B to A. Neither the symmetric form nor a logarithmic change is offered, and the asymmetry is never mentioned.
- Only the two endpoints take part. There is no mode that accepts a series and reports a change per step, and no annualised or compound variant — a move spanning several years entered as two figures comes back as one flat percentage.
Tested and documented by itoolnet, the team that builds and maintains this site.