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Percentage Calculator

One tool, 5 calculators: find a percentage of a number, discover what percent one value is of another, calculate percentage increase or decrease, track percentage change, and reverse a percentage back to the original number.

5
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Why Use This Percentage Calculator?

  • ✓ Covers every common percentage problem in one place.
  • ✓ Ideal for finance, discounts, tips, grades, statistics, and business growth.
  • ✓ Step-by-step formulas, worked examples, and a quick reference table included.

On This Page

Percentage Calculator Quick Reference Table Percentage Formulas Worked Examples Best Practices FAQs Related Calculators

Percentage Calculator

What is X% of Y?

Use this to calculate tips, discounts, taxes, exam scores, or any share of a total value.

Result
30

20% of 150 is 30.

X is what percent of Y?

Use this to find test scores, market share, completion rates, or any part-to-whole comparison.

Result
20%

30 is 20% of 150.

Percentage change between two values

Use this to measure growth or decline in sales, prices, weight, population, or any metric over time.

Result
+25%

80 increased to 100, a change of +25%.

Increase or decrease a number by a percentage

Use this for price markups, discounts, raises, pay cuts, or applying a fixed percentage adjustment.

Result
230

200 increased by 15% is 230.

X is Y% of what number?

Use this to find an original price before a discount, or a total before a known share of it.

Result
160

40 is 25% of 160.

Quick Percentage Reference Table

Percentage Of 50 Of 100 Of 500 Of 1,000

Percentage Formulas

Percentage of a Number

Result = (Percentage ÷ 100) × Number

X is What Percent of Y

Percentage = (X ÷ Y) × 100

Percentage Change

% Change = ((New − Old) ÷ Old) × 100

Percentage Increase/Decrease

New Value = Number × (1 ± Percentage ÷ 100)

Reverse Percentage

Original Number = X ÷ (Percentage ÷ 100)

Worked Examples

Example 1 — What is 15% of 80?

(15 ÷ 100) × 80 = 12

Example 2 — 45 is what percent of 180?

(45 ÷ 180) × 100 = 25%

Example 3 — Price change from $60 to $75

((75 − 60) ÷ 60) × 100 = +25% increase

Example 4 — Decrease 120 by 30%

120 × (1 − 0.30) = 84

Example 5 — 18 is 20% of what number?

18 ÷ 0.20 = 90

Where Percentage Calculations Are Used

🛍 Shopping & Discounts

Calculate sale prices, discounts, markups, and sales tax on purchases.

💰 Finance & Investing

Track interest rates, investment returns, loan payments, and portfolio growth.

🎓 Grades & Test Scores

Convert raw scores into percentages and calculate weighted grade averages.

📊 Business & Statistics

Measure growth rates, market share, conversion rates, and year-over-year change.

🍽 Tipping & Bills

Work out restaurant tips, service charges, and bill splits quickly.

⚖ Health & Nutrition

Calculate body fat percentage, macro splits, and weight change over time.

Best Practices & Common Mistakes

✅ Best Practices

  • Always confirm which number is the "whole" before dividing.
  • Use percentage change (not a flat difference) to compare growth over time.
  • Keep extra decimal places for financial or scientific calculations.
  • Double-check whether a rate is applied once or compounds repeatedly.
  • Label increases and decreases clearly to avoid sign confusion.

❌ Common Mistakes

  • Confusing percentage change with percentage points.
  • Using the new value instead of the original as the base.
  • Forgetting that a decrease followed by the same percentage increase does not return the original value.
  • Rounding too early in multi-step calculations.
  • Mixing up "of" and "is" in word problems.

Frequently Asked Questions

Multiply the number by the percentage and divide by 100. For example, 20% of 150 is (20 ÷ 100) × 150 = 30.
Divide the part by the whole and multiply by 100. For example, 30 is what percent of 150: (30 ÷ 150) × 100 = 20%.
Percentage change is a relative measure based on the original value, while percentage points measure the raw difference between two percentages. Going from 20% to 30% is a change of 10 percentage points, but a 50% relative increase.
Subtract the original value from the new value, divide by the original value, then multiply by 100. A positive result means an increase and a negative result means a decrease.
A reverse percentage finds the original number when you already know a value and the percentage it represents. Divide the known value by the percentage expressed as a decimal: X ÷ (percentage ÷ 100).
Yes. Percentages over 100% simply mean the part is larger than the whole it is being compared to, which is common when measuring growth or increases.
Because each percentage is applied to a different base value. Decreasing 100 by 10% gives 90, but increasing 90 by 10% only gives 99, not 100.
Yes. All five calculators use standard, internationally recognized percentage formulas and calculate results instantly in your browser.

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