The Ultimate Guide to Percentages
Percentages are everywhere. From figuring out the tip at a restaurant and calculating the discount on a pair of shoes, to analyzing business growth and grading exam papers, understanding how to calculate percentages is a fundamental life skill.
The word "Percent" literally translates to "per century" or "out of 100." When we say 50%, we are simply saying "50 out of every 100." Our 5-in-1 calculator above handles every single real-world percentage scenario you will encounter. Below is exactly how the math works.
1. How to Calculate a Basic Percentage
This is the most common use case. You want to find a specific slice of a whole number. For example: "What is 20% of 500?"
Result = (Percentage × Number) ÷ 100Example: (20 × 500) ÷ 100 = 100.
2. How to Calculate Percentage Increase
Used mostly in business and finance. If your salary was $50,000 last year and is $60,000 this year, you want to know your exact growth rate.
Increase = ((New Value - Original Value) ÷ Original Value) × 100Example: ((60,000 - 50,000) ÷ 50,000) × 100 = 20% Increase.
3. How to Calculate Percentage Decrease
Used to measure weight loss, stock market drops, or dropping sales numbers. If a website had 2,000 visitors yesterday and only 1,500 today, what was the drop?
Decrease = ((Original Value - New Value) ÷ Original Value) × 100Example: ((2,000 - 1,500) ÷ 2,000) × 100 = 25% Decrease.
4. How to Calculate a Discount
You are shopping and see a TV for $800 with a "15% Off" sticker. How much will you actually pay at the register?
Discount Amount = (Original Price × Discount %) ÷ 100Formula 2 (Final Cost):
Final Price = Original Price - Discount AmountExample: $800 × 15% = $120 Saved. Final price is $680.
5. Find What Percentage X is of Y
This is the "Exam Score" formula. If you answered 45 questions correctly out of a total of 60 questions, what is your grade?
Percentage = (Part ÷ Total) × 100Example: (45 ÷ 60) × 100 = 75%.
Frequently Asked Questions (FAQs)
Is "50% of 20" the same as "20% of 50"?
Yes! This is a fascinating mathematical trick called the commutative property of multiplication. 50% of 20 is 10. And 20% of 50 is also 10. You can always reverse the numbers to make mental math easier!
How do I add a 20% tip mentally?
To quickly find 20% without a calculator, just move the decimal point of the total bill one spot to the left (which gives you 10%), and then double it. If the bill is $45.00, 10% is $4.50. Double that is $9.00.