Percentage Calculator

How to Calculate a Percentage of a Number

To find what X% of a number Y is, multiply Y by X and divide by 100. For example, to find 20% of 150: multiply 150 × 20 = 3,000, then divide by 100 = 30. This is the most common percentage calculation used for tips, discounts, and tax.

Common examples

• 15% of 50 = 7.5 — typical restaurant tip
• 20% of 200 = 40 — 20% discount on $200 item
• 8% of 500 = 40 — 8% sales tax on $500 purchase
• 10% of 1000 = 100 — 10% raise on $1,000 salary

How to Calculate Percentage Change

Percentage change tells you how much a value increased or decreased relative to its starting point. Subtract the old value from the new value, divide by the old value, then multiply by 100. A positive result means an increase; negative means a decrease.

Common examples

• 100 to 120 = +20% increase — salary raise
• 200 to 150 = −25% decrease — price drop
• 50 to 75 = +50% increase — investment growth
• 1000 to 800 = −20% decrease — budget cut

How to Calculate Percentage Difference

Percentage difference compares two values without a defined starting point — useful when neither value is the "original." Subtract the smaller from the larger, divide by their average, then multiply by 100. Unlike percentage change, order doesn't matter.

Common examples

• 100 and 150 = 40% difference
• 200 and 250 = 22.22% difference
• 500 and 750 = 40% difference

Tip Calculator — How Much to Tip

Tipping is one of the most common uses for a percentage calculator. The standard tip in the US is 15–20% for restaurants. To calculate a tip, multiply your bill by the tip percentage and divide by 100. For a $45 bill with an 18% tip: 45 × 18 ÷ 100 = $8.10.

Quick tip reference

• 15% tip: $30 bill → $4.50 | $50 bill → $7.50 | $100 bill → $15
• 18% tip: $30 bill → $5.40 | $50 bill → $9 | $100 bill → $18
• 20% tip: $30 bill → $6 | $50 bill → $10 | $100 bill → $20
• 25% tip: $30 bill → $7.50 | $50 bill → $12.50 | $100 bill → $25

Discount Calculator — Sale Price

To find the sale price after a discount, calculate the discount amount first, then subtract it from the original price. For a 30% discount on a $200 item: 30% of 200 = $60, so the sale price is $200 − $60 = $140. Alternatively, multiply by (1 − discount%) = 200 × 0.70 = $140.

Common discount calculations

• 10% off: $50 → save $5 | $100 → save $10 | $500 → save $50
• 20% off: $50 → save $10 | $100 → save $20 | $500 → save $100
• 25% off: $80 → save $20 | $200 → save $50 | $400 → save $100
• 50% off: $100 → save $50 | $300 → save $150 | $1000 → save $500

Frequently Asked Questions