Percentage Calculator

Calculate percentages instantly — percent of a number, percent change, and more.

Percentage Calculator
What is X% of Y?

How to use:

  • • What is X% of Y? - Find a percentage of a number
  • • X is what percent of Y? - Find what percent one number is of another
  • • Percent change - Calculate percentage increase or decrease

What Is a Percentage?

A percentage is a way of expressing a number as a fraction of 100. The word itself comes from the Latin "per centum," meaning "out of a hundred." Percentages show up everywhere in daily life: your phone battery is at 73%, a sale offers 20% off, your income tax rate is 22%, a student scores 91% on an exam, and a sports team wins 60% of its games. They give us a universal, intuitive scale for comparing quantities regardless of the original totals.

This calculator solves the three core percentage problems you encounter most often. First, finding what P% of a number X is — useful for calculating tips, discounts, or tax amounts. Second, figuring out what percentage one number is of another — handy for test scores or market share. Third, computing percent change between two values — essential for tracking price moves, growth rates, and statistical shifts. Enter your values, choose the calculation type, and get the answer instantly with a full explanation.

How to Use This Calculator

  1. 1Choose the type of calculation you need: "What is P% of X?", "X is what % of Y?", "Percent change from X to Y", or "X is P% of what number?"
  2. 2Enter the numbers in the input fields that appear for your chosen calculation type.
  3. 3Click the Calculate button to run the calculation.
  4. 4Read the result — the calculator shows the final answer along with a plain-language explanation of how it was computed.

Percentage Formulas

1. What is P% of X? Result = X × (P / 100) 2. X is what % of Y? Percentage = (X / Y) × 100 3. Percent change from X to Y: Change % = ((Y − X) / |X|) × 100 Positive = increase, Negative = decrease 4. X is P% of what number? Whole = X / (P / 100)

Formula 3 uses the absolute value of the original number |X| in the denominator. This handles cases where the starting value is negative — for example, a loss turning into a gain — and ensures the direction of change (increase vs. decrease) is captured by the sign of the result, not by a quirk of the original value.

Worked Examples

What is 15% of $85? (Restaurant tip)

Use formula 1: Result = 85 × (15 / 100) = 85 × 0.15 = $12.75. A 15% tip on an $85 restaurant bill comes to $12.75, making your total $97.75. You can also check this mentally: 10% of $85 is $8.50, and 5% is half of that ($4.25), so 15% = $8.50 + $4.25 = $12.75.

A stock goes from $120 to $156 — how much did it gain?

Use formula 3: Change % = ((156 − 120) / |120|) × 100 = (36 / 120) × 100 = 0.3 × 100 = 30% increase. The stock price rose by $36, which represents a 30% gain from the original $120. If the price had instead dropped to $96, the change would be ((96 − 120) / 120) × 100 = −20%, a 20% decrease.

You scored 42 out of 50 on a test — what is your grade?

Use formula 2: Percentage = (42 / 50) × 100 = 0.84 × 100 = 84%. Scoring 42 correct answers out of 50 total questions gives you an 84% grade. In most grading scales that lands solidly in the B range. If the test had been scored out of 60 and you answered 42 correctly, the percentage would be (42 / 60) × 100 = 70%.

Frequently Asked Questions

How do you calculate a percentage increase?▾
Subtract the original value from the new value, divide by the original value, then multiply by 100. Formula: ((New − Original) / |Original|) × 100. For example, if a price rises from $50 to $65, the increase is ((65 − 50) / 50) × 100 = 30%. A positive result means an increase; a negative result means a decrease.
What is the difference between percent and percentage point?▾
A percent is a relative change, while a percentage point is an absolute difference between two percentages. If an interest rate rises from 4% to 6%, that is a 2 percentage-point increase — but it is a 50% increase in relative terms ((6 − 4) / 4 × 100). Mixing up the two is one of the most common errors in reporting financial and statistical data.
How do you find the original price before a discount was applied?▾
Use the reverse percentage formula: Original = Sale Price / (1 − Discount%). For example, if an item is on sale for $68 after a 15% discount, the original price is 68 / (1 − 0.15) = 68 / 0.85 = $80. You can verify: 15% of $80 = $12, and $80 − $12 = $68. This is the same as formula 4 in our calculator ("X is P% of what number?").
How do you calculate compound percent growth over multiple periods?▾
For compound growth you cannot simply add percentages — you must apply each percentage change sequentially. The formula is: Final = Start × (1 + r)^n, where r is the growth rate as a decimal and n is the number of periods. For example, $1,000 growing at 8% per year for 5 years: $1,000 × (1.08)^5 = $1,469.33. Our Compound Interest calculator handles multi-period growth in detail.
What is a basis point and how does it relate to percentages?▾
A basis point (bp or bps) is one-hundredth of a percentage point, i.e., 0.01%. Basis points are used in finance to describe small changes in interest rates, bond yields, and fees with precision. For example, if a mortgage rate rises from 6.50% to 6.75%, that is a 25-basis-point increase. The term avoids ambiguity: saying "rates rose 0.25%" could be interpreted as a relative change, but "25 bps" is always an absolute difference.