The formulas this calculator uses
There isn't one single "percentage formula" — there are three, one for each type of question. Here's exactly which formula runs behind each box above, with a worked example for each.
1. What is X% of Y
Result = (X ÷ 100) × Y
Example: what is 20% of 150? → (20 ÷ 100) × 150 = 0.2 × 150 = 30
2. X is what percent of Y
Result = (X ÷ Y) × 100
Example: 30 is what percent of 120? → (30 ÷ 120) × 100 = 0.25 × 100 = 25%
3. Percentage change from A to B
Result = ((B − A) ÷ A) × 100
Example: change from 80 to 100 → ((100 − 80) ÷ 80) × 100 = (20 ÷ 80) × 100 = 25% increase
How to Calculate Percentage of Marks
Calculating the percentage of marks is one of the most common uses of a percentage calculator. Whether you're a student checking your exam results or a teacher preparing a grade sheet, the formula is simple:
Percentage of Marks = (Marks Obtained ÷ Total Marks) × 100
Example: If you scored 480 out of 600 → (480 ÷ 600) × 100 = 80%
If you have multiple subjects, add up all your marks and divide by the total maximum marks across all subjects. For example, if you scored 85 in Maths (out of 100), 90 in Science (out of 100), and 75 in English (out of 100), your total is 250 out of 300 → (250 ÷ 300) × 100 = 83.33%.
How to Calculate Percentage in Excel
Excel makes percentage calculations extremely easy with built-in formulas. To calculate what percentage one number is of another in Excel:
- Enter the part value in cell A1 (e.g., 30).
- Enter the whole value in cell B1 (e.g., 120).
- In cell C1, type =A1/B1
- Right-click cell C1, select "Format Cells," and choose "Percentage."
The result will display as 25%. To calculate what is X% of Y in Excel, use the formula =X%*Y or =(X/100)*Y.
Percentage Calculator for Money
Percentages are used constantly with money — tips at restaurants, discounts while shopping, taxes on purchases, and interest on loans. To calculate a percentage of any amount of money:
Amount = (Percentage ÷ 100) × Total Money
Example: 15% tip on a $200 bill → (15 ÷ 100) × 200 = $30
Percentage Difference Calculator
Percentage difference is different from percentage change. While percentage change uses the original value as the base, percentage difference compares two values relative to their average. The formula is:
Percentage Difference = |A − B| ÷ ((A + B) ÷ 2) × 100
Example: Difference between 80 and 100 → |80 − 100| ÷ ((80 + 100) ÷ 2) × 100 = 20 ÷ 90 × 100 = 22.22%
Add Percentage Calculator
An add percentage calculator helps you add a percentage to a number — useful for calculating prices with GST, VAT, tips, or markups. The formula is:
Final Value = Original Value × (1 + Percentage ÷ 100)
Example: Add 18% GST to ₹1,000 → 1000 × (1 + 18 ÷ 100) = 1000 × 1.18 = ₹1,180
Grade Percentage Calculator
Teachers and students often need to convert raw scores into grade percentages. The formula is the same as percentage of marks:
Grade % = (Marks Obtained ÷ Total Marks) × 100
Common letter grade ranges used in many schools and universities:
| Grade | Percentage Range |
|---|---|
| A | 90–100% |
| B | 80–89% |
| C | 70–79% |
| D | 60–69% |
| F | Below 60% |
What a percentage actually measures
A percentage is a way of describing part of something as if the whole were split into exactly one hundred equal pieces. The word itself comes from the Latin "per centum," meaning "by the hundred." When you say a shirt is 30% cotton, you are saying that if the fabric were divided into 100 equal parts, 30 of those parts would be cotton. This hundred-part frame is what makes percentages so easy to compare across completely different situations.
The three questions a percentage calculator answers
Almost every real-world percentage problem falls into one of three shapes. The first is "what is X% of Y" — for example, working out a 20% tip on a $150 bill. You solve this by turning the percentage into a decimal (divide by 100) and multiplying: 20 ÷ 100 × 150 = 30. The second shape flips the question around: "X is what percent of Y" — say, figuring out what share 30 correct answers make up out of 120 total questions. Here you divide the part by the whole and multiply by 100: (30 ÷ 120) × 100 = 25%. The third shape is percentage change, used whenever a value moves from one number to another over time, such as a price going from 80 to 100. You take the difference, divide by the original value, and multiply by 100: ((100 − 80) ÷ 80) × 100 = 25% increase.
Where percentages show up day to day
Percentages sit quietly behind an enormous number of everyday decisions. A restaurant bill, a loan's interest rate, a battery indicator, exam results, election polling, a nutrition label's "daily value," and a sale sign in a shop window are all percentages doing different jobs.
A common mixup: percentage vs. percentage point
One mistake worth avoiding is confusing a percentage change with a percentage point change. If an interest rate moves from 5% to 7%, that is a 2 percentage point increase, but it is a 40% increase relative to the original rate (2 ÷ 5 × 100).
Tips for calculating percentages without a tool
For quick mental estimates, it helps to know that finding 10% of a number is as simple as moving the decimal point one place to the left, and every other round percentage can be built from there — 5% is half of 10%, 20% is double 10%, and 15% is 10% plus 5%.
How to use this calculator
- Pick the box that matches your question — "what is X% of Y", "X is what % of Y", or percentage change.
- Type your numbers into the input fields.
- The answer updates instantly as you type — no button to press.
- Use the formula box above if you want to do the same calculation by hand next time.
Related calculators
You might also find these tools useful:
- Calculate discounts and sale prices with our Discount Calculator.
- Add GST to any amount with our GST Calculator.
- Calculate loan repayments with our EMI Calculator.
Frequently asked questions
How do I calculate a percentage of a number?
Divide the percentage by 100 and multiply it by the number. For example, 20% of 150 is (20 ÷ 100) × 150 = 30.
How do I find what percentage one number is of another?
Divide the part by the whole and multiply by 100. For example, 30 out of 120 is (30 ÷ 120) × 100 = 25%.
How do I calculate my percent?
To calculate your percent score, divide the number you got by the total possible number, then multiply by 100. For example, if you scored 45 out of 60, your percentage is (45 ÷ 60) × 100 = 75%.
What is 20% out of 70?
20% of 70 is 14. You calculate it as (20 ÷ 100) × 70 = 0.2 × 70 = 14.
How to calculate the percentage?
The basic formula is: Percentage = (Part ÷ Whole) × 100. For example, if you have 30 out of 120, the percentage is (30 ÷ 120) × 100 = 25%.
How to calculate percentage of marks?
To calculate the percentage of marks, divide the total marks you obtained by the maximum possible marks, then multiply by 100. For example, if you scored 480 out of 600, your percentage is (480 ÷ 600) × 100 = 80%.
How to calculate percentage in Excel?
In Excel, use the formula =Part/Whole and format the cell as a percentage. For example, if A1 contains 30 and B1 contains 120, then =A1/B1 gives 0.25, which displays as 25% when formatted as a percentage.
How do you calculate percentage difference?
Percentage difference is calculated as |A − B| ÷ ((A + B) ÷ 2) × 100. It measures how different two values are relative to their average, unlike percentage change which uses the original value as the base.
What is an add percentage calculator?
An add percentage calculator helps you add a percentage to a value — for example, adding 18% GST to a price. The formula is: Final Value = Original Value × (1 + Percentage ÷ 100).
How do you calculate percentage for money?
To calculate a percentage of money, multiply the amount by the percentage and divide by 100. For example, 15% of $200 is (15 ÷ 100) × 200 = $30. This is useful for tips, discounts, taxes, and interest.
How do you calculate grade percentage?
To calculate grade percentage, divide the marks obtained by the total marks, then multiply by 100. For example, 85 out of 100 is 85%. Many schools use letter grades based on ranges: A (90-100%), B (80-89%), C (70-79%), D (60-69%), F (below 60%).
How do I calculate percentage increase or decrease?
Subtract the original value from the new value, divide by the original value, then multiply by 100. A rise from 80 to 100 is ((100 − 80) ÷ 80) × 100 = 25%.
Is a percentage point the same as a percentage?
No. If a rate moves from 5% to 7%, that's a 2 percentage point increase, but a 40% increase relative to the original 5% figure.