Percentage Change Calculator
Enter an old value and a new value to see the percent increase or decrease, the absolute difference, and the relative variance.
This calculator runs entirely in your browser. Nothing you type is uploaded or stored.
How to use this tool
Type the original number in the "Old value" field and the new number in the "New value" field, then press Calculate. The percentage change calculator shows whether the value went up or down, the percent of that change, and the plain difference between the two numbers. Use Copy result to grab a clean text summary, or Clear to start over.
The formula
To calculate the increase or decrease percent, subtract the old value from the new value, divide by the absolute size of the old value, and multiply by 100. A positive result is an increase, a negative result is a decrease. The absolute difference is simply new minus old. The relative variance described on this page is the same percentage figure, often used when comparing a budget to actual spending or a forecast to a real outcome.
A real example
Say a product cost 200 dollars last year and now costs 250 dollars. The difference is 250 - 200 = 50. Divide by the old value: 50 / 200 = 0.25. Multiply by 100 and you get a 25% increase, with an absolute difference of 50 dollars. If instead the price dropped from 250 to 200, the percent difference between the two values would be -20%, a decrease of 50 dollars.
Common questions
What is the difference between percent change and absolute difference?
The absolute difference is just new minus old measured in the original units, such as dollars or units sold. The percent change scales that difference against the starting value, so it tells you how big the move was relative to where you began.
How do I calculate a percent increase versus a percent decrease?
Use the same formula for both. If the new value is larger than the old value the result is positive, which is an increase. If the new value is smaller the result is negative, which is a decrease. This tool labels each case for you.
Why does the old value need to be non-zero?
The formula divides by the old value, and dividing by zero is undefined. If your starting value is zero there is no meaningful percentage change to report, only the absolute difference.
What is relative variance?
Relative variance compares a result to a baseline as a percentage, for example actual sales against a forecast. It is the same calculation as percent change, with the baseline acting as the old value.
Are negative starting values supported?
Yes. The tool divides by the absolute size of the old value so the percentage stays meaningful, while still reporting the true signed difference between the two numbers.