Percentage Calculator

Percentage Calculator

Mode 1: What is X% of Y?

% of

Mode 2: X is what % of Y?

is what % of

Mode 3: Percentage Change from X to Y

Percentage Calculator – Complete Guide

Our free percentage calculator handles all three common percentage problems in one place. Whether you need to find a percentage of a number, determine what percent one value represents of another, or compute a percentage increase or decrease, this tool gives you an instant answer without needing a formula.

The Three Percentage Formulas Explained

Mode 1 – What is X% of Y? This is the most common percentage calculation. Formula: Result = (X ÷ 100) × Y. Example: What is 20% of 150? Answer: (20 ÷ 100) × 150 = 30. Used for discounts, tax amounts, and tips.

Mode 2 – X is what % of Y? Formula: Percentage = (X ÷ Y) × 100. Example: 45 is what percent of 180? Answer: (45 ÷ 180) × 100 = 25%. Used for test scores, market share, and composition ratios.

Mode 3 – Percentage change from X to Y. Formula: Change = ((Y − X) ÷ |X|) × 100. A positive result means an increase; negative means a decrease. Example: Price went from $80 to $100 — that is a 25% increase.

Real-World Applications

  • Shopping discounts: A 30% off sale on a $250 item saves you $75.
  • Sales tax: An 8% tax on a $60 purchase adds $4.80.
  • Grade calculation: 72 correct out of 90 questions = 80%.
  • Salary raise: Going from $50,000 to $55,000 is a 10% increase.
  • Investment returns: A portfolio grew from $10,000 to $13,500 — a 35% gain.
  • Body weight change: Losing 8 kg from 80 kg is a 10% reduction.

Why Percentages Matter

Percentages are one of the most universally used mathematical concepts in daily life. They appear in nutrition labels, bank interest rates, election results, sports statistics, weather forecasts, and financial reports. Understanding percentages helps you make smarter decisions about money, health, and data.

Frequently Asked Questions

How do I calculate a percentage discount?
Use Mode 1. Enter the discount percentage in X and the original price in Y. The result is the discount amount. Subtract it from the original price to get the sale price.
What is the difference between percentage point and percent change?
A percentage point is an absolute arithmetic difference between two percentages (e.g., from 10% to 15% is 5 percentage points). Percent change is relative: (15−10)/10 × 100 = 50% increase. These are often confused in financial and political reporting.
Can I calculate percentage decrease with Mode 3?
Yes. Enter the larger original value in X and the smaller new value in Y. The calculator will automatically show the result as a percentage decrease with the correct sign.
What if the original value is zero in Mode 3?
Percentage change from zero is mathematically undefined (division by zero). The calculator will hide the result in this case. If your original value is zero, the concept of percentage change does not apply.
How accurate are the results?
Results are rounded to four decimal places, which is more than sufficient for virtually all real-world percentage calculations including financial and scientific work.