Percentage Calculator

A percentage is a way of expressing a number as a fraction of 100. The word comes from the Latin per centum, meaning "per hundred." Understanding percentages is one of the most practical math skills you can have — they appear in discounts, grades, statistics, tax, interest rates, and everyday measurement.

The fundamental percentage formula is: Percentage = (Part ÷ Whole) × 100.

For example, if 16 out of 80 students passed an exam, the pass rate is (16 ÷ 80) × 100 = 20%.

Every percentage problem falls into one of three types:

• Type 1 — What is X% of Y? Example: What is 15% of 240? Answer: (15/100) × 240 = 36.
• Type 2 — X is what percent of Y? Example: 36 is what percent of 240? Answer: (36/240) × 100 = 15%.
• Type 3 — X is P% of what number? Example: 36 is 15% of what? Answer: 36 ÷ 0.15 = 240.

The formula for percentage change is: Change% = ((New − Old) ÷ Old) × 100.

If a price rose from $50 to $75: ((75 − 50) ÷ 50) × 100 = 50% increase. If it fell from $75 to $50: ((50 − 75) ÷ 75) × 100 = −33.3% decrease.

Percentages are everywhere. A 20% discount on a $60 item means you pay $60 × 0.80 = $48. A 6% sales tax on $120 means you add $120 × 0.06 = $7.20. An exam score of 43 out of 50 is (43/50) × 100 = 86%.

Memorise these common percentage equivalents to speed up mental math:

• 10% of a number = divide by 10
• 25% = divide by 4
• 50% = divide by 2
• 75% = multiply by 3, divide by 4
• 1% = divide by 100, then move decimal 2 places

See also: Discount Calculator | Percentage Change Calculator | Full Percentage Guide