# Percentage Calculator

> Three percentage tools in one: percent of a value, ratio as a percent, and percent change.

URL: https://uttir.com/percentage-calculator
Categories: calculators, math-tools
Privacy: Calculations run locally in your browser.

## About

The three most common percentage questions, answered side by side: “What is X% of Y?”, “X is what percent of Y?”, and “What is the percent change from X to Y?”. Results update as you type.

Percent change uses the standard formula (new − old) ÷ |old| × 100, so decreases show as negative values.

## How to use

1. **Pick the card that matches your question** — Each card is one of the three classic percentage problems.
2. **Enter the numbers** — The answer appears instantly below the inputs.

## Examples

### Tip on a bill

15% of a $200 bill.

Input:

```
15% of 200
```

Output:

```
30
```

### Discount as a percent

Paying 75 for something listed at 100.

Input:

```
75 of 100
```

Output:

```
75%
```

### Price increase

From 50 to 75.

Input:

```
50 → 75
```

Output:

```
+50%
```

## FAQ

### How is percent change calculated?

As (new − old) divided by the absolute value of old, times 100. A rise from 50 to 75 is +50%; a fall from 75 to 50 is −33.33%.

### Why is division by zero shown as a dash?

Percentages of or changes from zero are mathematically undefined, so the tool shows a dash instead of a misleading number.

### What is percentage change?

((new - old) / old) * 100. If a value goes from 100 to 120, the percentage change is +20%. If it goes from 100 to 80, it is -20%. The tool handles the direction automatically.

### How is "X% of Y" calculated?

The formula is (X / 100) × Y. For "what percent is A of B", the formula is (A / B) × 100. The tool handles both directions and rounds to your chosen precision.

## Related tools

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- [BMI Calculator](https://uttir.com/bmi-calculator) — Calculate your Body Mass Index and see where you fall on the healthy range.
- [Grade Calculator](https://uttir.com/grade-calculator) — Average your grades and work out what you need on the final to reach your target.
- [Date Calculator](https://uttir.com/date-calculator) — Count the days between two dates, or add and subtract days from any date.
- [Profit Margin Calculator](https://uttir.com/margin-calculator) — Calculate profit, margin, and markup from cost and selling price — or find the price needed for a target margin.

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For the full HTML page with the live tool, visit https://uttir.com/percentage-calculator.
This file is the markdown rendering at https://uttir.com/percentage-calculator.md. See https://uttir.com/llms.txt for a site-wide summary.