Percentage Increase Calculator
Calculate the percentage increase or decrease between an old and a new value, with the signed percent change and the exact difference.
ToolsSoup's Percentage Increase Calculator works out exactly how much a value went up or down between two numbers. Enter the original value and the new value, and you instantly get the percentage change (positive for an increase, negative for a decrease), the raw difference between the two numbers, and the new value expressed as a percent of the old one. It is the fast way to answer questions like "what is the percentage increase from 80 to 100?" for prices, salaries, traffic, weight, scores, and any before-and-after comparison. Everything runs in your browser — no uploads, no sign-up, and your numbers never leave your device.
What is a percentage increase calculator?
A percentage increase calculator measures how much a number has grown relative to where it started, expressed as a percentage. If the new value is larger than the old value the result is a percentage increase; if it is smaller, the result is a percentage decrease (a negative number). This tool is built specifically for before-and-after comparisons, so instead of remembering the formula you just type the two values and read off the percent change, the exact difference, and the ratio between them.
How to calculate percentage increase
Calculating a percentage increase takes three quick steps, and this tool does them automatically as you type:
- Enter the original (old) value in the first field — this is your starting point or baseline.
- Enter the new value in the second field — the value after the change.
- Read the percentage change: a positive percent means an increase, a negative percent means a decrease, and the difference field shows the raw amount the value moved.
What is the percentage increase formula?
The percentage increase formula is: ((new value − old value) ÷ |old value|) × 100. First find the difference by subtracting the old value from the new value, then divide that difference by the absolute starting value, and finally multiply by 100 to turn it into a percentage. For example, going from 80 to 100 is ((100 − 80) ÷ 80) × 100 = 25%, a 25% increase. The same formula gives a negative result for a decrease — going from 100 to 80 is −20%.
Percentage increase vs percentage decrease
Increase and decrease use the same formula; only the sign of the result differs. When the new value is bigger than the old value the percent change is positive and we call it an increase, and when the new value is smaller the percent change is negative and we call it a decrease. A subtle point: the percentage is always measured against the original value, so a rise from 80 to 100 (+25%) and a fall from 100 to 80 (−20%) do not cancel out, because each is measured against a different starting number.
Why use this percentage increase calculator?
- Purpose-built for before-and-after comparisons: enter an old value and a new value and get the answer immediately.
- Shows the signed percentage change so you instantly know whether it is an increase or a decrease.
- Also gives the raw difference and the new value as a percent of the old, for a complete picture.
- Updates live as you type — there is no calculate button to press.
- Runs entirely in your browser, so your numbers are private, and it is 100% free with no ads or sign-up.
Frequently asked questions
How do I calculate the percentage increase between two numbers?
Subtract the old value from the new value, divide by the old value, and multiply by 100. For example, from 80 to 100 is ((100 − 80) ÷ 80) × 100 = 25%. Enter both numbers above and the calculator does it for you instantly.
What is the percentage increase from 80 to 100?
It is a 25% increase. The difference is 20, and 20 divided by the starting value of 80 is 0.25, which is 25%.
Can this calculator also show a percentage decrease?
Yes. If the new value is smaller than the old value, the percentage change comes out negative and the calculator labels it as a decrease. For example, going from 100 to 80 shows −20%.
Why isn't a 25% increase cancelled out by a 25% decrease?
Because each percentage is measured against a different starting value. Increasing 100 by 25% gives 125, but decreasing 125 by 25% gives about 94, not 100. The percentage always refers to the value you started from.
What happens if the original value is zero?
Percentage increase from zero is undefined, because you cannot divide by zero, so the percent change shows a dash. The calculator still shows the raw difference between the two values in that case.