# Percentage Calculator

Free online percentage calculator. Find X% of Y, calculate what percent one number is of another, or compute percentage change between two values.

## What this calculates

Quickly solve any percentage problem with this free online calculator. Whether you need to find what percentage one number is of another, calculate a percentage of a value, or determine the percentage change between two numbers, this tool handles it all instantly.

## Inputs

- **Calculation Mode** — options: Find X% of Y, X is what % of Y?, Percentage change from X to Y — Select the type of percentage calculation you need.
- **Value X**
- **Value Y**

## Outputs

- **Result** — The calculated percentage result.
- **Explanation** — formatted as text — Step-by-step explanation of the calculation.

## Details

Percentages are one of the most commonly used mathematical concepts in daily life. From calculating discounts and tips to analyzing data and financial returns, understanding percentages is essential.

How Percentage Calculations Work

- Find X% of Y: Multiply Y by X/100. For example, 15% of 200 = (15/100) x 200 = 30.

- X is what % of Y: Divide X by Y, then multiply by 100. For example, 30 is what % of 200? (30/200) x 100 = 15%.

- Percentage Change: Subtract the old value from the new value, divide by the absolute value of the old value, and multiply by 100. For example, change from 200 to 250 = ((250-200)/200) x 100 = 25% increase.

Percentage calculations are foundational in finance (interest rates, returns on investment), retail (discounts, markups), science (concentration, error rates), and education (test scores, grading curves).

## Frequently Asked Questions

**Q: How do I calculate a percentage of a number?**

A: To find X% of a number Y, divide X by 100 and multiply by Y. For example, to find 25% of 80: (25/100) x 80 = 20. This works because 'percent' literally means 'per hundred.'

**Q: How do I find what percentage one number is of another?**

A: Divide the part by the whole and multiply by 100. For example, if you scored 45 out of 60 on a test: (45/60) x 100 = 75%. This tells you that 45 is 75% of 60.

**Q: What is the difference between percentage change and percentage difference?**

A: Percentage change measures the change from an original value to a new value: ((new - old) / |old|) x 100. Percentage difference compares two values without a clear 'original': (|A - B| / ((A + B) / 2)) x 100. Use percentage change when there is a clear before/after relationship.

**Q: Can a percentage be greater than 100%?**

A: Yes. A percentage greater than 100% simply means that the value exceeds the reference amount. For example, if a stock price goes from $50 to $150, the percentage change is 200%, meaning it tripled in value.

**Q: How do I reverse a percentage? For example, if a price after 20% discount is $80, what was the original?**

A: If a 20% discount results in $80, the discounted price represents 80% of the original (100% - 20% = 80%). So the original price = $80 / 0.80 = $100. In general, original = discounted price / (1 - discount rate).

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Source: https://vastcalc.com/calculators/math/percentage
Category: Math
Last updated: 2026-04-21