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Percentage Calculator — Free Online Percent Tool

Calculate percentage, percentage change (increase/decrease), and what percent one number is of another. Free, instant, runs in your browser.

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How to calculate percentage change

Switch to the % change mode, enter the original value and the new value. The tool applies the formula ((new - original) / original) × 100and tells you whether it's an increase or decrease.

Find what percent one number is of another

Use the X is what % of Y mode. Divide the part by the whole and multiply by 100. For example, 25 out of 200 = (25 / 200) × 100 = 12.5%.

Private and instant

All math runs locally in your browser. No signup, nothing uploaded — results update as you type.

Frequently Asked Questions

How do I calculate percentage change?
Percentage change = ((new value - original value) / original value) × 100. A positive result is an increase; a negative result is a decrease. Enter both values and the tool computes it instantly.
How do I find what percent one number is of another?
Divide the part by the whole and multiply by 100. For example, 25 out of 200 = (25 / 200) × 100 = 12.5%.
Is this percentage calculator free?
Yes, completely free with no signup or limit. All math runs locally in your browser.