Free Percent Online Calculator
Quickly solve percentage problems for discounts, grades, tips, growth rates, and more. Choose a section below and enter your numbers.
1) What is X% of Y?
Example: What is 15% of 240?
2) X is what percent of Y?
Example: 30 is what percent of 120?
3) Percent increase or decrease
Example: from 80 to 100 = 25% increase.
How to use this percentage calculator
This percent online calculator combines three of the most common percentage formulas in one place. Whether you're checking a sale price, calculating tax, measuring business growth, or figuring out exam scores, you can get a precise answer in seconds.
Enter values as whole numbers or decimals. The calculator handles both positive and negative values, which is useful when working with losses, refunds, or downward changes.
Common percentage formulas
1. Percentage of a number
Formula: Result = (Percent ÷ 100) × Number
Use this when you need to find a specific fraction of a value, like 18% tip on a restaurant bill or 7.5% tax on a purchase.
2. What percent one number is of another
Formula: Percent = (Part ÷ Whole) × 100
This is ideal for grade calculations, conversion rates, and completion percentages. For example, if you finished 42 tasks out of 60, your completion is 70%.
3. Percent increase/decrease
Formula: Percent Change = ((New − Old) ÷ Old) × 100
Use this for investment performance, salary changes, population trends, traffic growth, or cost inflation.
Real-life use cases
- Shopping: Calculate discounts and final prices before checkout.
- Personal finance: Compare monthly budget changes and savings rates.
- Education: Turn test scores into percentages quickly.
- Business analytics: Track growth rates in leads, revenue, or retention.
- Health and fitness: Measure body weight change over time.
Worked examples
Example A: Discount price
A jacket costs $120 and is marked down 25%. First calculate 25% of 120 = 30. Then subtract 30 from 120. Final price = $90.
Example B: Grade percentage
You got 37 questions correct out of 50. Compute (37 ÷ 50) × 100 = 74%.
Example C: Monthly growth
Your website visits rose from 8,000 to 10,400. Percent change = ((10,400 − 8,000) ÷ 8,000) × 100 = 30% increase.
Tips for accurate percentage calculations
- Double-check whether you're solving for a part, a percent, or a change.
- Use the original value as the denominator in percent change calculations.
- When old value is 0, percent change is undefined (division by zero).
- Keep enough decimal places for financial or scientific work, then round at the end.
Final thoughts
A reliable percentage calculator saves time and prevents mental-math mistakes. Bookmark this tool whenever you need a fast percent finder, a percent increase calculator, or an easy way to answer “what percent is this?”