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Online Percentage Calculator

Calculate percentages, increases, decreases and rates quickly with our free tool.

Percent of a number

Enter percent
Enter base number
Example
20% of 100 = 20

Apply percentage increase

Enter number to increase
Enter increase percentage
Example
100 + 2% = 102

Apply percentage decrease

Enter number to decrease
Enter decrease percentage
Example
100 - 20% = 80

What percentage is A of B?

Enter number to compare
Enter reference number
Example
25 of 100 = 25%

Percentage change

Enter end value
Enter start value
Example
From 100 to 125 = +25% change

What is a percentage?

A percentage is a share "out of a hundred". 15% means 15 out of 100, i.e. 0.15. This lets you compare values and measure changes.

Percentages are used for discounts, grades, statistics and price or population trends.

Basic formulas

  • Part of whole: Part = Total × % / 100.
  • Percentage: % = (Part / Total) × 100.
  • Increase: End = Start × (1 + %/100).
  • Decrease: End = Start × (1 − %/100).
  • Change rate: ((End − Start) / Start) × 100.

Short method

First decide whether you are calculating a part of a whole or a change between two values, then apply the right formula.

Tip: 10% = divide by 10, 5% = half of 10%, 20% = double 10%.

Percentage vs percentage points

Don't confuse "+5 percentage points" and "+5%". From 20% to 25% is +5 points, but +25% relative increase.

Examples

20% of 150 = 30.

Discount: 150 − 20% = 120.

Increase: 80 → 100 = +25%.

Part: 25 of 100 = 25%.

Change rate: 153 → 187 = ((187−153)/153) × 100 ≈ 22.2%.

Quick reference

  • 1% = 1/100 of the whole.
  • 5% = 1/20 of the whole.
  • 25% = 1/4 of the whole.
  • 50% = half of the whole.
  • 75% = three quarters of the whole.

Typical uses

  • Discounts, promotions, VAT, sale prices.
  • Grades, averages, school results.
  • Budget, statistics, data trends.
  • Comparing shares (market, surveys, population).

Common mistakes

  • Confusing "part of whole" and "change".
  • Forgetting to divide by 100 after multiplying.
  • Applying the percentage to the wrong base.
  • Interpreting a point drop as a percentage drop.

FAQ

  • Increase vs percentage of a total? One compares a change, the other a share.
  • Different result? Check whether you're calculating a share, a decrease or a change.
  • Need a step-by-step explanation? The Math AI assistant can explain in detail.