Free Online Percentage Calculator

Percentage calculations are a fundamental part of everyday math, used universally for figuring out retail sales tax, calculating shopping discounts, tracking business growth, or grading academic tests. Our free, multi-function percentage calculator tool takes the guesswork out of complex mathematics by applying three standard percentage formulas automatically.

1. Standard Percentage Value Formula (Find X% of Y)

Use this mode to find a specific fraction of a whole number.
Formula: (Percentage ÷ 100) × Total Value
Example: 20% of 50 is (20/100) × 50 = 10.

2. Percentage Proportion Formula (X is what % of Y)

Use this mode when you know the part and the total, but need to find the exact percentage.
Formula: (Part ÷ Total) × 100
Example: 10 is what percent of 50? (10/50) × 100 = 20%.

3. Find the Original Number (X is Y% of what?)

This reverse calculation helps you accurately find the original total when you only know the current percentage and the fractional part.
Formula: Part ÷ (Percentage ÷ 100)

Frequently Asked Questions (FAQ)

How do I calculate percentage increases and decreases?

To manually find a percentage change or difference, calculate the exact numerical difference between the two numbers, divide that difference by the original starting number, and multiply the final result by 100. This calculation is heavily used in corporate finance and marketing to track profit margins, sales growth, and web traffic changes over time.