Percentage Change Calculator

Tracking growth, losses, or price differences is much clearer when expressed as a percentage. The Percentage Change Calculator compares an old value and a new value to instantly show the exact percent increase or decrease, along with the raw numeric difference. It handles all cases correctly, including negative starting values and changes that result in values over 100%, making it versatile for financial, scientific, and everyday comparisons. Percentage change is directional by design — the original value is always the reference — which distinguishes it from percentage difference, where no value is treated as the baseline. This calculator is commonly used to measure year-over-year revenue growth, track personal fitness milestones, evaluate investment performance, and analyse trends in any data set where you need to communicate movement from one value to another in a standardised, universally understood format. The raw numeric difference is shown alongside the percentage so you can see both the relative and absolute magnitude of the change in a single view.

The calculator subtracts the old value from the new value to find the raw numeric difference. That difference is then divided by the absolute value of the original number, which ensures correct sign handling even when the starting value is negative — for example, a recovery from a loss. Multiplying by 100 converts the proportion into a percentage. A positive result means the value increased from old to new, while a negative result means it decreased. The calculator also shows the raw numeric difference alongside the percentage, so you can see both the relative and absolute magnitude of the change at a glance. Note that the original value cannot be zero, since percentage change is mathematically undefined when dividing by zero.