Three percentage modes

Percentage Calculator

Choose the mode that matches your question, enter the two numbers, and get the result with the exact formula used.

Calculate a percentage

Pick the question that matches your task. The inputs and result will follow that mode.

Choose your percentage question Find amount 15% of 80 Find percent 15 is what % of 60 Find change 80 to 100

Use this when you know the percentage and the base number.

Percentage (%)

Base number

Part value

Whole value

Original value

New value

Use the right percentage mode

Percent of a number

Use when you know the percent and the base: 15% of 80.

result = percent / 100 × number

Part as a percent

Use when you know the part and whole: 15 is what percent of 60?

percent = part / whole × 100

Percent change

Use when a value moves from one number to another: 80 to 100.

change = (new - old) / old × 100

Real calculator example

Find 15% of 80

This matches the default mode in the calculator above.

Percentage: 15
Base number: 80
Calculation: 80 × 15 / 100
Result: 12

Quick checks before you trust the result

If the question says "of", use the base number as the amount being multiplied.
For discounts, subtract the percentage result from the original price.
For percent change, the original value is the denominator. Reversing old and new changes the answer.

Frequently Asked Questions

How do I convert a percentage to a decimal?

Divide by 100. For example, 15% becomes 0.15 before multiplying by the base number.

Why is percentage change based on the original value?

The original value is the starting point. A move from 80 to 100 is 20 divided by 80, so the change is 25%.

Can I use negative values?

Yes. Negative values work mathematically, but make sure the sign matches the real context of your problem.