Percentage Calculator

How to use the Percentage Calculator

1. Select your calculation mode: "X% of Y," "X is what % of Y," or "% Change."
2. Enter your numbers in the input fields. The result appears instantly as you type.
3. Review the formula shown alongside the result to verify the math.
4. Use the quick-reference buttons below the result to see common percentages of your number at a glance.

The percentage-change trap

If a price drops 50% and then rises 50%, it does not return to the original price. A $100 item drops to $50 (−50%), then a 50% increase on $50 is only $25, bringing it to $75. Percentage changes are relative to whatever value they're calculated from, not to some fixed original. This is why "prices rose 20%, then fell 20%" always nets out to a small overall decrease, not zero.

Frequently asked questions

How do I calculate a percentage increase?

Subtract the original value from the new value, divide by the original value, and multiply by 100. The calculator's "percentage change" mode does this automatically and tells you whether it's an increase or decrease.

How is "X is what percent of Y" different from "what is X% of Y"?

The first finds what proportion one number represents of another (e.g., 30 is what % of 120 → 25%); the second applies a known percentage to a number (e.g., 25% of 120 → 30). Same numbers, opposite direction. Pick the mode that matches your question.

Why do reverse-percentage results sometimes look odd with negative numbers?

Percentage change involving a negative starting value doesn't behave intuitively (division by a negative flips the sign); if your original value can be negative, sanity-check the result rather than trusting the sign blindly.