Percentage Increase/Decrease Calculator
Enter an old value and a new value to instantly see the percentage change between them — updates live as you type, no button needed.
How to Use the Percentage Change Calculator
- Enter the starting ("Old") value — for example, last month's sales figure.
- Enter the ending ("New") value — for example, this month's sales figure.
- The percentage increase or decrease is calculated and displayed instantly as you type.
- A green result means an increase; a red result means a decrease.
Why Use This Tool?
What formula does this calculator use?
It uses the standard percentage change formula: ((New − Old) ÷ Old) × 100. If the result is positive, it's labeled a percentage increase; if it's negative, it's labeled a percentage decrease. The tool always shows the absolute percentage along with the correct label so there's no confusion about direction.
What happens if the old value is 0?
Percentage change is mathematically undefined when the starting value is 0, since you can't divide by zero. In that case, the tool shows a friendly message instead of an error — if the new value is also 0, it notes there's no change; otherwise it explains that percentage change can't be calculated from a zero starting point and suggests using a plain difference instead.
Who uses a percentage change calculator?
Students learning percentages, teachers building worked examples, shoppers comparing sale prices, and anyone tracking changes in sales, weight, prices, or scores relies on quick percentage change math. This tool removes the manual arithmetic so you get an instant, accurate answer.
Is this calculator free and private?
Yes — completely free, no signup required, and every calculation happens directly in your browser. Nothing you enter is ever sent to a server or stored anywhere.