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Percentage Calculator

Calculate percentages instantly — find what percent of a number is, determine what percentage one value is of another, or find the percentage change between two numbers.

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What is the percentage increase/decrease from to ?

What Is a Percentage?

A percentage is a way of expressing a number as a fraction of 100. The word comes from the Latin per centum, meaning “out of a hundred.” When you say 25%, you mean 25 out of every 100 — or equivalently, one quarter of any total.

Percentages appear everywhere: discounts, interest rates, exam scores, battery levels, and statistics all rely on percentage notation because it provides an instantly comparable scale regardless of the underlying quantity.

The Three Core Percentage Calculations

1. Finding a Percentage of a Number

Formula: Result = (Percentage ÷ 100) × Number

Example: What is 18% of 250? 18 ÷ 100 = 0.18 → 0.18 × 250 = 45

This is the most common type: calculating a tip, a discount amount, a tax, or a commission.

2. Finding What Percentage One Number Is of Another

Formula: Percentage = (Part ÷ Whole) × 100

Example: What percentage is 45 out of 180? (45 ÷ 180) × 100 = 25%

Use this when you want to express a score, a share, or a ratio as a percentage. Getting 36 out of 40 questions right is (36 ÷ 40) × 100 = 90%.

3. Percentage Change (Increase or Decrease)

Formula: Change = ((New Value − Old Value) ÷ |Old Value|) × 100

A positive result means an increase; a negative result means a decrease.

Examples:

  • Sales grew from 400 to 500 units: ((500 − 400) ÷ 400) × 100 = 25% increase
  • Temperature fell from 20°C to 15°C: ((15 − 20) ÷ 20) × 100 = 25% decrease

Practical Examples

SituationCalculationResult
20% off a $60 item0.20 × 60$12 discount
Scored 42 out of 50(42 ÷ 50) × 10084%
Salary raised from $50k to $55k((55k − 50k) ÷ 50k) × 10010% increase
Stock fell from $80 to $64((64 − 80) ÷ 80) × 10020% decrease
Population tripled from 1,000 to 3,000((3,000 − 1,000) ÷ 1,000) × 100200% increase

Percentage vs. Percentage Points

These two terms are frequently confused.

Percentage points measure an absolute difference between two percentages. If an interest rate rises from 3% to 5%, that is a 2 percentage-point increase.

Percentage change measures a relative difference. That same rise from 3% to 5% is a 66.7% increase (because 2 ÷ 3 × 100 ≈ 66.7%).

News reports often say “the rate rose by 2%” when they mean 2 percentage points — which can significantly understate the relative change.

How to Reverse a Percentage

If you know a value after a percentage was applied and want to find the original, divide by the multiplier:

  • After an increase of P%: Original = Result ÷ (1 + P/100)
  • After a decrease of P%: Original = Result ÷ (1 − P/100)

Example: A jacket costs $130 after a 30% markup. What was the original price? 130 ÷ 1.30 = $100

Example: A discounted price of $85 reflects a 15% discount. What was the original? 85 ÷ (1 − 0.15) = 85 ÷ 0.85 = $100

Frequently Asked Questions

How do I calculate a percentage of a number?

Multiply the number by the percentage and divide by 100. For example, 15% of 200 = (15 × 200) / 100 = 30. Alternatively, convert the percentage to a decimal (15% = 0.15) and multiply: 0.15 × 200 = 30.

How do I find what percentage one number is of another?

Divide the part by the whole and multiply by 100. For example, to find what percentage 30 is of 200: (30 / 200) × 100 = 15%.

How is percentage increase calculated?

Subtract the original value from the new value, divide by the original value, and multiply by 100. Formula: ((new − old) / |old|) × 100. For example, an increase from 80 to 100 is ((100 − 80) / 80) × 100 = 25% increase.

How is percentage decrease calculated?

The same formula as percentage change applies. If the new value is smaller than the original, the result is negative — that magnitude is the percentage decrease. For example, a drop from 100 to 80: ((80 − 100) / 100) × 100 = −20%, which is a 20% decrease.

Can percentage change be more than 100%?

Yes. A 100% increase means the value doubled. A 200% increase means it tripled. For example, going from 50 to 200 is a 300% increase: ((200 − 50) / 50) × 100 = 300%.

What is the difference between percentage change and percentage points?

Percentage points describe an absolute difference between two percentages: going from 20% to 30% is a 10 percentage-point increase. Percentage change describes a relative difference: that same move from 20% to 30% is a 50% increase (because 10 / 20 × 100 = 50%). These are often confused in news reporting.

How do I reverse a percentage calculation?

To find the original value before a percentage was applied, divide by (1 + percentage/100) for an increase, or by (1 − percentage/100) for a decrease. For example, a price of $120 after a 20% increase means the original was 120 / 1.20 = $100.