Percentage Calculator

Three types of percentage calculations, all in one place.

What is X% of Y?

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X is what percent of Y?

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Percentage change from X to Y

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About Percentage Calculator

This tool solves the three most common percentage problems in one place: finding X% of a number, determining what percentage one number is of another, and calculating the percentage change (increase or decrease) between two values. Results update instantly as you type.

Calculation modes explained

  • What is X% of Y? — Multiplies Y by X/100. For example: 20% of 150 = 30. Use this for calculating discounts, tax amounts, or tips.
  • X is what % of Y? — Divides X by Y and multiplies by 100. For example: 45 is 30% of 150. Use this for grades, market share, and composition ratios.
  • Percentage change from X to Y — Calculates ((Y − X) / |X|) × 100. Use this for price changes, growth rates, or comparing before-and-after values.

Common use cases

Percentage calculations appear in everyday life — calculating a restaurant tip, finding a sale discount, working out a student's grade, comparing salary increases, or analysing revenue growth. This calculator handles all of them without requiring you to remember the formulas.

About the Percentage Calculator

Percentage calculations show up everywhere: discounts on a shopping receipt, interest on a savings account, exam marks, tax adjustments, performance comparisons, and tip estimation. The arithmetic is straightforward but the mental gymnastics — "what is 15% of 280?", "100 is what percentage of 320?", "10 went to 12, what is the percentage increase?" — are surprisingly error-prone under time pressure. A dedicated calculator handles each of the standard percentage questions without ambiguity.

This calculator supports four common operations: percentage of a number (what is X% of N), the percent that one number is of another (X is what % of N), percentage change between two numbers (from A to B), and adding or subtracting a percentage from a number (tax-style adjustments).

The four common percentage questions

Most everyday percentage problems are one of: (1) X% of N — multiply X/100 by N; (2) X is what % of N — divide X by N and multiply by 100; (3) percentage change from A to B — (B − A) / A × 100; (4) add or subtract X% from N — N × (1 ± X/100). Memorising these four removes 90% of percentage confusion.

Percentage points vs. percent change

A frequent source of misreporting in headlines: if interest rates rise from 4% to 5%, that is a 1 percentage point increase, but a 25 percent increase (because 1 is 25% of 4). The two are not interchangeable. When comparing rates, statistics, or shares of a total, be explicit about which form you mean.

How to use the Percentage Calculator

  1. Pick the operation

    Choose the calculation you need — percent of a number, one number as a percent of another, percentage change, or add/subtract.

  2. Enter the values

    Fill in the two input fields. The result updates instantly; no submit button.

  3. Read both forms

    For percentage change, both the absolute and relative differences are shown so you can pick the form that fits your context.

Worked examples

Example 1

Input: 15% of 280

Result: 42

Typical "tip" or "discount" calculation.

Example 2

Input: 100 is what % of 320

Result: 31.25%

Used for budget shares, exam marks, and similar.

Example 3

Input: From 10 to 12

Result: +20%

Increase relative to the starting value of 10.

Example 4

Input: Add 8.5% sales tax to 49.99

Result: 54.24

Adding a percentage is multiplying by 1 + (rate/100).

Real-world use cases

  • Calculating tips, discounts, and sales tax at the till.
  • Comparing year-over-year growth in business reports.
  • Working out exam marks and grade percentages.
  • Estimating savings on advertised "% off" sales.
  • Calculating commission or bonus amounts as a percentage of revenue.

Tips & common mistakes

  • A percentage above 100 simply means more than the original — a 300% increase is four times the starting value.
  • Be careful chaining percentage changes: a 10% drop followed by a 10% rise does not return to the original (it lands at 99% of the start).
  • When comparing percentages, ensure the bases are the same. "10% of 1000" and "10% of 100" are very different absolute numbers.

Frequently asked questions

How do I find a percentage in my head?

For 10%, move the decimal one place to the left (10% of 245 = 24.5). For 1%, two places (1% of 245 = 2.45). Combine these to get others: 15% = 10% + 5% = 24.5 + 12.25 = 36.75.

What does a negative percentage change mean?

A decrease. From 100 to 80 is −20% (the value fell by 20% of the starting value).

How is percentage change different from percentage points?

Percentage points are an absolute difference between two percentages; percentage change is the relative change. From 4% to 5% is +1 percentage point and +25% relative change.

Related tools

→ Tip Calculator→ Compound Interest→ Loan & EMI Calculator

Last updated: June 2026 · All processing happens locally in your browser.