Percentage Calculator
Solve everyday percentage problems including percent of a number, percentage increase, percentage decrease, discounts, sales tax, tips, grades, and part-to-whole comparisons. Enter the values you know, calculate the result, then use the examples and formulas below to understand what the percentage means.
Percentage Calculator Tips
Percentages are easiest when you first decide what the original amount is and what question you are answering. Use percent of for part-of-a-number questions, percent change for increases or decreases, and part divided by whole for what-percent questions. The same 20% can mean $4, $40, or $400 depending on the base amount.
Quick Guide
- Identify the original or whole amount before calculating.
- Use percent of when you need a portion of a number.
- Use percent change when comparing old and new values.
- Keep extra decimal places until the final answer.
Percent Of a Number
Find amounts such as 15% of 80, 20% of a bill, or 7.5% sales tax.
Percent Change
Calculate percentage increase or decrease when comparing an old value with a new value.
Real-World Uses
Handle discounts, grades, tips, markups, statistics, tax, and finance comparisons.
Common Percentage Formulas
Percentages compare a part to a whole using a base of 100. The most important step is identifying the base number, because every percentage answer depends on what the percent is being taken from.
- Percent of a number: number × percent ÷ 100
- What percent is A of B: A ÷ B × 100
- Percent increase: (new − old) ÷ old × 100
- Percent decrease: (old − new) ÷ old × 100
Worked Percentage Examples
Example 1: 15% of 80 is 80 × 15 ÷ 100 = 12. Example 2: if a price increases from $40 to $50, the increase is $10 and the percent increase is 10 ÷ 40 × 100 = 25%. Example 3: if a $75 item is 20% off, the savings are $15 and the sale price is $60.
Quick Percentage Reference Table
| Percent | Of 50 | Of 100 | Of 250 | Of 500 | Of 1,000 |
|---|---|---|---|---|---|
| 5% | 2.5 | 5 | 12.5 | 25 | 50 |
| 10% | 5 | 10 | 25 | 50 | 100 |
| 15% | 7.5 | 15 | 37.5 | 75 | 150 |
| 20% | 10 | 20 | 50 | 100 | 200 |
| 25% | 12.5 | 25 | 62.5 | 125 | 250 |
| 50% | 25 | 50 | 125 | 250 | 500 |
When to Use a Percentage Calculator
Use this calculator when you need a fast percent answer for shopping discounts, restaurant tips, school grades, sales tax, commission rates, price increases, weight changes, sports stats, finance returns, or any part-to-whole comparison.
- Discounts: find savings and sale prices.
- Grades: compare points earned with total points possible.
- Finance: compare rates, returns, fees, and growth.
- Everyday math: split amounts, compare sizes, and estimate changes.
Common Percentage Mistakes
The most common mistake is using the wrong base number. A change from 50 to 60 is a 20% increase, but a change from 60 down to 50 is a 16.67% decrease because the starting number is different. Another common mistake is rounding too early in a multi-step problem.
Percentage Calculator FAQs
What is a percentage?
A percentage is a way of expressing a number as part of 100. For example, 25% means 25 out of every 100.
How do I calculate 20% of a number?
Multiply the number by 20 and divide by 100. You can also multiply the number by 0.20.
What is the difference between percent and percentage points?
Percent is a relative change. Percentage points are the direct difference between two percentages, such as 40% to 45% being a 5 percentage point increase.
How do I calculate percentage increase?
Subtract the old number from the new number, divide by the old number, and multiply by 100.
How do I calculate percentage decrease?
Subtract the new number from the old number, divide by the old number, and multiply by 100.
Why does the original number matter?
The original number is the base of the comparison. Changing the base changes the percentage result.