What is the percentage calculator — 3 types of % problems?
In short
25% of 200 = 50. To find what percent 30 is of 120: 30 ÷ 120 × 100 = 25%. A price change from $80 to $100 is a 25% increase. Three formulas cover all common percentage problems.
Solves the three most common percentage calculations: finding a percentage of a number, expressing one number as a percentage of another, and calculating the percent change between two values.
How to use this calculator
- 1Select the type of percentage problem from the dropdown.
- 2Enter the two numbers involved in your calculation.
- 3Read the result and the explanation showing the math.
The formula
- X
- — First value or percentage
- Y
- — Second value (base)
- Old/New
- — Original and new values for percent change
Worked example
The scenario
What is 15% of $85?
The result
(15/100)×85 = $12.75. This is the standard restaurant tip calculation on an $85 bill.
Common use cases
- Calculating tips, discounts, and tax amounts
- Finding a test score percentage
- Tracking price increases or salary raises
- Determining what portion of a budget you spent
Limitations & assumptions
- Percent change formula uses absolute value of the original, so changes from a negative base may be unintuitive.
- Does not handle compound percentage changes (e.g., 10% then 10% is not 20%).
Frequently asked questions
How do you calculate a percentage?
How do you find what percent one number is of another?
How do you calculate percent change?
What is the percentage difference vs percentage change?
How do I reverse a percentage (find the original price)?
Disclaimer: KalkWise calculators are provided for general informational and educational purposes only and do not constitute financial, investment, tax, or legal advice. Results are estimates based on the figures you enter and the assumptions described above. Actual outcomes will vary. Consult a qualified professional before making financial decisions.