Anyone who’s ever looked at a test score, a sale price, or a budget spreadsheet has needed to work out a percentage. The good news: you don’t need a math degree to get it right. This guide walks you through the core formula, real examples like finding 20% of 70 or calculating exam marks, and how to handle percentages in Excel — all with clear steps you can use today.
Basic percentage formula: (part / whole) × 100 = percentage · Example: 20% of 70: 14 · Example: 30% of 300: 90 · Percentage of marks formula: (marks obtained / total marks) × 100
Quick snapshot
- Formula: part ÷ whole × 100 (Microsoft Support)
- Example: What percent is 20 of 70? 28.57% (Microsoft Support)
- Use for discounts, grades, statistics (Microsoft Support)
- Multiply number by percentage (as decimal)
- 20% of 70 = 70 × 0.2 = 14
- 30% of 300 = 300 × 0.3 = 90
- Total marks ÷ maximum marks × 100
- Example: 280 out of 500 = 56%
- Quick for report cards
- Excel: =part/total → format % (Academy of Learning Career College)
- Calculator: divide then multiply by 100 (Academy of Learning Career College)
- Use for budgets and money (Academy of Learning Career College)
The six facts below cover the core values you need when checking any percentage calculation.
| Fact | Value | Source |
|---|---|---|
| Percentage definition | A ratio expressed as a fraction of 100 | Microsoft Support |
| Core formula | Percentage = (part / whole) × 100 | Microsoft Support |
| 20% of 70 | 14 | Standard arithmetic |
| 30% of 300 | 90 | Standard arithmetic |
| 5% of 70 | 3.5 | Standard arithmetic |
| 40% of 80 | 32 | Standard arithmetic |
How do I calculate percentage?
The universal formula works for every scenario.
What is the percentage formula?
- Percentage = (part / whole) × 100 — this is the universal formula (Microsoft Support).
The “part” is the portion you care about; the “whole” is the total amount. Multiply the division result by 100 to express it as a percentage.
How to calculate percentage step by step
- Identify the part and the whole.
- Divide the part by the whole.
- Multiply the result by 100.
- Add the % sign.
Example: 20 out of 70. Part = 20, whole = 70. 20 ÷ 70 = 0.2857. 0.2857 × 100 = 28.57%. So 20 is 28.57% of 70.
The implication: once you learn the three-step rule, you never need to guess again.
How to calculate percentage of marks?
Students and teachers use this formula constantly.
How to calculate percentage of marks for multiple subjects?
- Formula: (marks obtained / total marks) × 100 (Microsoft Support).
If a student scores 280 out of 500 across five subjects: 280 ÷ 500 = 0.56; 0.56 × 100 = 56%.
How to calculate percentage of marks in exams
- Sum the marks obtained in each subject.
- Divide by the total possible marks.
- Multiply by 100.
Example: 45 out of 60 on a test. 45 ÷ 60 = 0.75; 0.75 × 100 = 75% (Academy of Learning Career College).
The pattern: this same method applies to any exam or report card.
How do I calculate 20% of an amount?
This is one of the most common percentage questions people ask.
How to find 20% of a number?
- 20% = 20/100 = 0.2. Multiply the amount by 0.2.
Example: 20% of 70 = 70 × 0.2 = 14.
Quick trick for 20%
- Divide the number by 5 (since 20% = 1/5). 70 ÷ 5 = 14.
This works for any amount: 20% of 300 = 300 ÷ 5 = 60.
The catch: dividing by 5 is faster and works every time.
How to calculate percentage of total?
Budgeting and data analysis rely on this formula.
How to calculate percentage from total in Excel?
- Excel formula: =part/total. Then format the cell as a percentage. (Microsoft Support).
For example, to find what percentage 45 is of 60, enter =45/60 and apply Percent Style; Excel displays 75%.
Percentage of total formula
- Percentage of total = (part / total) × 100.
In a budget, if you spent $350 out of a total $1,000, your percentage of total is (350/1000)×100 = 35%.
The implication: Excel handles the multiplication by 100 for you.
How to calculate percentage in calculator?
With a calculator, the steps are straightforward.
How to calculate percentage of money?
- Enter the part, press ÷, enter the whole, press =, then multiply by 100.
To find 30% of $300: enter 300, press ×, enter 0.3, press =; result $90. Or use the % button if your calculator has one.
Using a calculator for percentages
- Most calculators: type the number, press ×, type the percentage (e.g., 20), press % — some models show the result directly.
Test: 20% of 70 on a standard calculator: 70 × 20 % = 14.
The pattern: calculator methods vary by model, but the logic stays the same.
Step-by-step guide to calculating percentage manually
- Identify the part and the whole. Example: you scored 35 points out of 50.
- Divide the part by the whole. 35 ÷ 50 = 0.7.
- Multiply by 100. 0.7 × 100 = 70.
- Add the percent sign. 70%.
That’s it. The same steps work for any scenario — marks, sales tax, discounts, or survey data.
Mastering the percentage formula means you can quickly evaluate deals, understand grades, and manage budgets without guessing. Even in Excel, the logic is identical — just let the software handle the multiplication by 100.
Confirmed facts
- Percentage formula: (part / whole) × 100 (Microsoft Support)
- 20% of 70 = 14
- 30% of 300 = 90
- 5% of 70 = 3.5
- 40% of 80 = 32
- Excel formula for percentage: =part/total (Academy of Learning Career College)
What’s unclear
- No major uncertainties — the basic percentage calculation is universally defined.
“A simple percentage example in Excel is =10/100, which returns 0.1 before formatting.”
— Microsoft Support (official documentation)
“Typing =45/60 and then formatting the cell as percentage yields 75%.”
— Academy of Learning Career College (Excel tutorial)
The pattern is clear: the core formula hasn’t changed in centuries. For students checking report cards, shoppers comparing discounts, or analysts building spreadsheets, the same three-step rule applies. The implication: once you learn it, you never need to guess again.
For a detailed tutorial with additional examples, you can calculate percentage step by step to see the formulas broken down clearly.
Frequently asked questions
How do you calculate 10% of a number?
Divide the number by 10. For example, 10% of 200 = 20.
How do you find the percentage of a total?
Use the formula: (part ÷ total) × 100.
What is the easiest way to calculate percentages?
Convert the percentage to a decimal and multiply. For 20% of 70, use 70 × 0.2 = 14.
How do you calculate percentage increase or decrease?
Find the difference, divide by the original value, multiply by 100.
How do you convert a fraction to a percentage?
Divide the numerator by the denominator, then multiply by 100.
How do you calculate percentage off a price?
Multiply the original price by the discount percentage (as a decimal) and subtract.
How do you calculate percentage in Excel without a formula?
Use the quick analysis tool or simply type =number/total and press Enter, then click Percent Style.
What is 15% of 200?
15% of 200 = 200 × 0.15 = 30.
Noah Foster is Senior Reporter at Australian Insight, covering breaking stories and explainers.