Percentage Calculator

A percentage calculator is a versatile math tool that helps you solve the three most common percentage problems: finding a percentage of a number, determining what percentage one number is of another, and calculating the percentage change between two values. Percentages are used daily in finance, shopping, academics, cooking, health, and countless other areas.

Our free online percentage calculator provides three distinct calculation modes to cover every percentage scenario you might encounter. Whether you need to figure out the sale price of an item (What is 25% of $80?), determine your test score (42 is what percent of 50?), or analyze growth rates (percentage change from 100 to 150), this tool gives you instant, accurate results.

The calculator handles decimal values, negative numbers, and large numbers with precision, displaying results with up to 6 decimal places. All calculations are performed in real time as you type, providing immediate feedback without needing to click a calculate button.

This is a client-side tool that runs entirely in your browser. No data is sent to any server, and no personal information is collected. Use it as many times as you need, completely free.

1. Select a calculation mode — Choose from "What is X% of Y?", "X is what % of Y?", or "% Change" depending on your calculation needs.
2. "What is X% of Y?" — Enter the percentage and the number. For example, enter 15 and 200 to find that 15% of 200 is 30.
3. "X is what % of Y?" — Enter the part and the whole. For example, enter 30 and 200 to find that 30 is 15% of 200.
4. "% Change" — Enter the original value and the new value. For example, from 100 to 125 shows a 25% increase.
5. View results — Results appear instantly as you type, showing both the calculation description and the answer.
6. Reset — Click Reset to clear all values and start a new calculation.

The percentage calculator uses three fundamental formulas:

What is X% of Y?
Result = (X / 100) × Y
Example: What is 15% of 200? → (15 / 100) × 200 = 30

X is what % of Y?
Percentage = (X / Y) × 100
Example: 30 is what % of 200? → (30 / 200) × 100 = 15%

Percentage Change:
Change = ((New Value - Old Value) / |Old Value|) × 100
Example: From 100 to 125 → ((125 - 100) / 100) × 100 = 25% increase

The absolute value in the percentage change formula ensures correct calculation even when the original value is negative.