Percentage Calculator

What is 15% of 200? 45 is what percent of 180? 80 is 40% of what number? Your price increased by 12% — what's the new amount?

The percentage calculator handles all four question types instantly — enter any two known values and get your answer without touching a formula.

What Is a Percentage?

A percentage is a rate, number, or amount expressed as a fraction of 100 — represented by the symbol %.

Derived from the Latin per centum ("by the hundred"), percentages compare a value to a total of 100, making it easy to express ratios, probabilities, and changes in a universally understood format.

• 50% = half of the whole

• 100% = the complete whole

• 200% = twice the whole

• 1% = one hundredth of the whole

Where Percentages Are Used Every Day

• Discounts and sales prices

• Tax rates and VAT (Value Added Tax) calculations

• Test scores and grades

• Interest rates and loan repayments

• Statistics and probability

• Business growth and decline rates

Percentage Formulas — All Four Types

Type 1 — What is p% of x?

y = (x × p) ÷ 100

Example: What is 20% of 150? y = (150 × 20) ÷ 100 = 30

Type 2 — x is What Percent of y?

p = (x × 100) ÷ y

Example: 45 is what percent of 180? p = (45 × 100) ÷ 180 = 25%

Type 3 — x is p% of What?

y = (x × 100) ÷ p

Example: 80 is 40% of what? y = (80 × 100) ÷ 40 = 200

Type 4 — Percentage Increase or Decrease

y = ±x × (100 + p) ÷ 100

• For increase: y = x × (100 + p) ÷ 100

• For decrease: y = x × (100 − p) ÷ 100

Example: What is 250 increased by 20%? y = 250 × (100 + 20) ÷ 100 = 250 × 1.20 = 300

Example: What is 250 decreased by 20%? y = 250 × (100 − 20) ÷ 100 = 250 × 0.80 = 200

Core Percentage Formulas — Quick Reference

How to Use the Percentage Calculator

What is p% of x?

• Enter p (percentage) in the first field

• Enter x (the whole number) in the second field

• y = result auto-calculated

• Formula used: y = (x · p) / 100

x is What Percent of y?

• Enter x (the part) in the first field

• Enter y (the whole) in the second field

• p = percentage result auto-calculated

• Formula used: p = (x · 100) / y

x is p% of What?

• Enter x (the known part) in the first field

• Enter p (the percentage) in the second field

• y = the original whole auto-calculated

• Formula used: y = (x · 100) / p

What is x Increased/Decreased by p%?

• Select increased or decreased

• Enter x (original value) in the first field

• Enter p (percentage change) in the second field

• y = new value auto-calculated

• Formula used: y = ±x × (100 + p) / 100

How to Calculate Percentage — Step by Step Examples

Example 1 — Find Percentage of a Number

What is 15% of 300?

1. y = (300 × 15) ÷ 100

2. y = 4,500 ÷ 100

3. y = 45

Example 2 — Find What Percent

30 is what percent of 120?

1. p = (30 × 100) ÷ 120

2. p = 3,000 ÷ 120

3. p = 25%

Example 3 — Find the Original Value

60 is 30% of what number?

1. y = (60 × 100) ÷ 30

2. y = 6,000 ÷ 30

3. y = 200

Example 4 — Percentage Increase

A product costs $80. Price increases by 15%. New price?

1. y = 80 × (100 + 15) ÷ 100

2. y = 80 × 1.15

3. y = $92

Example 5 — Percentage Decrease

A salary of $5,000 decreases by 10%. New salary?

1. y = 5,000 × (100 − 10) ÷ 100

2. y = 5,000 × 0.90

3. y = $4,500

Percentage Quick Reference Table

Quick Percentage Tips

• Reverse percentage trick: 10% of 50 is the same as 50% of 10 — both equal 5. This works for any two numbers and makes mental math faster

• Fast 10% rule: To find 10% of any number, move the decimal point one place to the left. 10% of 350 = 35. 10% of 4,200 = 420

• Excel formula: Use =Part/Total and format the cell as percentage — Excel handles the ×100 automatically

• Percentage vs percentage points: A rise from 20% to 25% is a 5 percentage point increase but a 25% relative increase — these are different things

Fun Fact That'll Make You Laugh 😄

The word "percent" comes from Latin per centum — meaning "by the hundred."

The Romans used percentages long before the % symbol existed — Emperor Augustus taxed goods at 1/100th of their value, which is literally 1%.

So the next time you complain about a 1% bank fee — just know that Julius Caesar was already doing it 2,000 years ago, and nobody stopped him either. 😂

Frequently Asked Questions

How do you calculate a percentage?

Divide the part by the whole and multiply by 100. Formula: (Part ÷ Whole) × 100 = Percentage. Example: 30 out of 120 = (30 ÷ 120) × 100 = 25%.

What is the percentage formula?

There are four core formulas: y = (x × p) ÷ 100 (find p% of x), p = (x × 100) ÷ y (find what percent), y = (x × 100) ÷ p (find the whole), and y = x × (100 ± p) ÷ 100 (find increase or decrease).

What is 20% of 150?

20% of 150 = (150 × 20) ÷ 100 = 30. Using the quick tip: 10% of 150 = 15, so 20% = 15 × 2 = 30.

How do you calculate a percentage increase?

Subtract the original value from the new value, divide by the original value, and multiply by 100. Formula: ((New − Original) ÷ Original) × 100. Example: price rises from $80 to $92 = ((92 − 80) ÷ 80) × 100 = 15% increase.