Percentage Calculator: Formula & Everyday Uses

A percentage calculatorsolves common percentage problems in seconds — find what percent one number is of another, calculate a percentage increase or decrease, or determine the percentage of a given number. Percentages are everywhere: shopping discounts, restaurant tips, test scores, tax rates, and financial returns. This guide covers the core formulas and practical scenarios.

The Three Basic Percentage Formulas

These three patterns cover the vast majority of everyday percentage questions. Once you know which situation you are in, you pick the matching formula and plug in the numbers. Our percentage calculator does all three automatically so you do not have to memorize anything.

How to Use the Percentage Calculator

The tool offers three modes, each corresponding to one of the basic formulas:

• Find percentage of a number: Enter the percentage and the total — get the portion instantly.
• Find what percent one number is of another: Enter the part and the whole — get the percentage.
• Find the percentage change: Enter the old value and the new value — get the increase or decrease as a percentage.

Common Use Cases

• Shopping: Calculate the sale price after a 20% discount or compare "buy one get one" offers.
• Dining: Quickly compute a 15% or 20% tip on the bill total.
• Grades: Find out what percentage score you need on a final exam to reach a target grade.
• Finance: Track investment returns, interest rates, and budget percentages.
• Business: Measure growth rates, profit margins, and market share changes.

FAQ

Q: How do I calculate a 20% tip on my bill?
A: Multiply the bill total by 0.20 (or use the percentage-of-a-number mode: 20% of total). For example, 20% of $45 = $9.

Q: What is the difference between percentage increase and percentage points?
A: If a rate rises from 4% to 6%, that is a 2 percentage-point increase but a 50% increase (2 ÷ 4 × 100 = 50%). Percentage points describe the arithmetic difference; percentage increase describes the relative change.

Q: Can I calculate reverse percentages?
A: Yes. If you know the final price after a 15% discount is $85, divide by 0.85 to find the original price ($100). Our calculator's "find original value" mode handles this automatically.