Back to Math & Statistics

How to Use Our Percentage Calculator

3 min read

How to Use Our Percentage Calculator

Percentages come up constantly -- sales tax, tips, discounts, test scores, investment returns. Our Percentage Calculator handles all common percentage calculations instantly.

The Three Main Calculations

What is X% of Y?

Enter the percentage and the base number. For example: "What is 15% of 200?" Answer: 30. Use this for calculating tips, discounts, tax amounts, and commission.

X is what percent of Y?

Enter two numbers to find the percentage relationship. For example: "45 is what percent of 180?" Answer: 25%. Use this for calculating grades, completion rates, and proportions.

Percentage Change

Enter the original value and the new value to find the percentage increase or decrease. For example: from 80 to 100 is a 25% increase. Use this for tracking price changes, growth rates, and performance metrics.

Common Uses

  • Shopping: A $120 item at 30% off = $120 - $36 = $84
  • Tipping: 20% tip on a $65 bill = $13
  • Grades: 42 out of 50 = 84%
  • Investing: A stock goes from $50 to $62 = 24% return

Quick Mental Math Tip

To find 10% of any number, move the decimal point one place left. Then adjust from there: 20% is double the 10% amount, 5% is half of 10%, and 15% is 10% plus half of 10%.

Related Calculators