Percentage Calculator — Find Percent Of, Increase, Decrease & More

This percentage calculator handles the three most common percent problems in one place: finding a percentage of a number, calculating a percentage increase or decrease, and determining what percentage one number is of another. Get instant answers without memorizing formulas.

Why use this Percentage Calculator?

  • Three calculation modes covering the most common percentage questions
  • Results update instantly as you type — no submit button needed
  • Displays both the formula used and the numeric answer
  • Free and works on any device, including mobile

How to use the Percentage Calculator

  1. Pick your calculation type: Choose from 'What is X% of Y?', 'X is what percent of Y?', or 'Percentage change from X to Y?' using the mode selector.
  2. Enter your numbers: Fill in the input fields — for example, type 15 and 200 to find 15% of 200.
  3. Read the instant result: The answer and the formula appear immediately below the inputs so you can see exactly how the calculation works.

Frequently Asked Questions

How do I calculate what percent one number is of another?

Divide the part by the whole and multiply by 100. For example, to find what percent 45 is of 180: (45 ÷ 180) × 100 = 25%. The calculator's 'X is what % of Y?' mode does this automatically.

How do I calculate a percentage increase or decrease?

The formula is: ((New Value − Old Value) ÷ Old Value) × 100. A positive result is an increase; a negative result is a decrease. For example, a price rising from $80 to $100 is a 25% increase: ((100 − 80) ÷ 80) × 100 = 25%.

What is 20% of 350?

20% of 350 is 70. The calculation is 350 × 0.20 = 70. You can verify this instantly using the 'What is X% of Y?' mode on this calculator.

How do I add a percentage to a number (like a tax or tip)?

Multiply the original number by (1 + percentage/100). For example, adding 8% tax to $50: $50 × 1.08 = $54. You can also find 8% of $50 ($4) using this calculator and add it mentally.

What's the difference between percentage points and percent change?

Percentage points measure the arithmetic difference between two percentages (e.g., a rate rising from 2% to 5% is a 3 percentage-point increase). Percent change is relative: that same move is a 150% increase relative to the starting value. The distinction matters in finance, polling, and economics.

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