Percentage Calculator

How to Use the Percentage Calculator

This calculator handles three of the most common percentage questions, each on its own mode. Choose "% of number" to take a portion of a value, "% change" to compare two values over time, or "what %" to express one number as a share of another. Enter the two numbers for whichever mode you pick and the answer appears instantly, with no rounding surprises.

The Three Percentage Formulas

A percent literally means "per hundred," so every calculation scales by 100. Finding a percentage of a number uses result = (percent ÷ 100) × number, so 15% of 200 is 0.15 × 200 = 30. Percentage change uses ((new − old) ÷ old) × 100, so a price moving from 80 to 100 is a (20 ÷ 80) × 100 = 25% increase. And "what percent is X of Y" uses (part ÷ whole) × 100, so 42 out of 50 is 84%.

Percentage Change vs. Percentage Points

A common source of confusion is that percentage change is always measured relative to the starting value, which keeps moving. A 50% drop followed by a 50% rise does not return to the original — $100 falls to $50, then rises only to $75. This also explains percentage points: an interest rate going from 10% to 15% is a 5 percentage-point rise, but a 50% relative increase. Keeping the base straight prevents costly misreadings of statistics.

Where Percentages Show Up

Percentages are the everyday language of proportion. You use them to add sales tax at checkout, work out a restaurant tip, gauge a discount while shopping, read the interest rate on a loan or savings account, track investment returns, and interpret news figures like inflation or poll results. Because the underlying formulas are easy to transpose, this calculator lets you jump between the three modes without re-learning the math each time.