Percentage Calculator
7 percentage calculators in one tool. Find X% of Y, calculate percentage increase & decrease, reverse percentages, discounts, tips & more — with instant results and step-by-step formula breakdown.
What is X% of Y?
Find a percentage of any number — for tips, discounts, test scores & more.
How to Use the Percentage Calculator
Select the calculator type using the tabs at the top. Each tab solves a different percentage problem — enter your values and the result appears instantly. The formula box shows the exact formula used and walks you through each calculation step so you understand the math.
Use the decimal places control to set precision from 0 to 4 decimal places. Click Copy to copy the result to your clipboard. Quick examples are available below the calculator for common real-world scenarios.
Percentage Formulas Explained
What is X% of Y?
Example: What is 20% of 500?
(20 ÷ 100) × 500 = 0.20 × 500 = 100
X is what percent of Y?
Example: 50 is what percent of 200?
(50 ÷ 200) × 100 = 0.25 × 100 = 25%
Percentage Increase
Example: Price rose from $100 to $150.
((150 − 100) ÷ 100) × 100 = 50% increase
Percentage Decrease
Example: Price dropped from $200 to $150.
((200 − 150) ÷ 200) × 100 = 25% decrease
Reverse Percentage (find original price)
Example: You paid $80 after a 20% discount. What was the original price?
80 ÷ (1 − 0.20) = 80 ÷ 0.80 = $100
Common Percentage Use Cases
Shopping discounts: Use the Discount tab to find the sale price and how much you save before buying. Enter the original price and the discount percentage.
Restaurant tips: The Tip Calculator tab calculates the tip amount and total bill. Enter the number of people to split the bill evenly between friends.
Salary raises: Use "Value After % Change" (Increase) to calculate your new salary after a raise. Or use "Reverse %" to find your pre-raise salary from your current pay.
Test scores: Use "X is what % of Y" to convert a score to a percentage — e.g. 43 correct out of 50 questions = (43 ÷ 50) × 100 = 86%.
Tax & VAT: Use "Value After % Change" (Increase) to add a sales tax or VAT percentage to a base price.
Frequently Asked Questions
How do I calculate a percentage of a number?
Use the formula: (X ÷ 100) × Y. For example, 20% of 500 = (20 ÷ 100) × 500 = 100. Enter the percentage and the number in the first tab for instant results.
What is the percentage increase formula?
Percentage increase = ((New − Old) ÷ Old) × 100. From 100 to 150 = ((150 − 100) ÷ 100) × 100 = 50% increase. Use the "% Change" tab.
How do I find the original price after a discount?
Use reverse percentage: Original = Final ÷ (1 − Discount%/100). If you paid $80 after 20% off: 80 ÷ 0.80 = $100 original. Use the "Reverse %" tab.
How do I calculate a percentage decrease?
Percentage decrease = ((Old − New) ÷ Old) × 100. From 200 to 150: ((200 − 150) ÷ 200) × 100 = 25% decrease. Use the "% Change" tab which auto-detects increases and decreases.
How do I split a restaurant bill with tip?
Use the Tip Calculator tab. Enter the bill amount, tip percentage (usually 15–20%), and the number of people. The calculator shows tip per person and total per person automatically.
Is this percentage calculator accurate?
Yes. All calculations use JavaScript's native floating-point arithmetic and are accurate to at least 10 significant figures. Use the precision control to display 0–4 decimal places.
Is this calculator free and private?
Completely free — no account, no signup, no premium tier. All calculations happen in your browser. Nothing is sent to any server. Your history is saved locally in your browser only.