01 · Calculators

Percentage Calculator

Four common percentage calculations in one place. Results update as you type and show the formula, so you can check the math.

What is X% of Y?

—

X is what percent of Y?

—

Percentage change

—

Increase or decrease by %

—

How to use the percentage calculator

  1. Pick the calculation that matches your question.
  2. Enter your numbers. Commas are fine (for example 1,250).
  3. Read the result and the formula used underneath it.

Percentage formulas explained

What is X% of Y?
result = X ÷ 100 × Y. Example: 20% of 150 = 0.2 × 150 = 30.
X is what percent of Y?
result = X ÷ Y × 100. Example: 30 is 20% of 150.
Percentage change from A to B
result = (B − A) ÷ |A| × 100. Example: from 50 to 75 is a 50% increase.
Increase or decrease Y by X%
result = Y × (1 ± X ÷ 100). Example: 200 increased by 15% = 230.

Percentage change vs. percentage points

If an interest rate rises from 4% to 5%, it has risen by 1 percentage point, but by 25 percent relative to where it started. Mixing these up is one of the most common percentage mistakes in reports and news articles.

Also note that percentage changes are not symmetric: a 50% drop followed by a 50% rise leaves you at 75% of the original value, not 100%.

Examples

A $80 jacket is 25% off

25% of 80 = 20, so the sale price is $60

Traffic grew from 1,200 to 1,500 visits

Percentage change = +25%

Questions

Why can’t I calculate percentage change from zero?

Percentage change divides by the starting value. When the starting value is zero, the result is undefined, so the calculator shows a message instead of a misleading number.

How many decimal places are shown?

Results are rounded to up to four decimal places for readability.

Can I use negative numbers?

Yes. Percentage change uses the absolute value of the starting number, so moving from −50 to −25 is shown as a 50% increase.