Percentage Calculator
Three ways to solve any percentage
How to Calculate Percentages
A percentage is a number expressed as a fraction of 100. This calculator handles three common percentage calculations: finding a percentage of a number, finding what percent one number is of another, and calculating percentage change.
Common percentage mistakes to avoid
Percentages can be confusing when the base number changes. A 20% increase followed by a 20% decrease does not return to the original value. Always check what number the percentage is being applied to before using the result.
Percentage Calculator: practical guide
The Percentage Calculator is built for people who want a fast answer without losing context. It keeps the calculation simple, shows the result clearly, and helps you understand what the number means before you use it in a real decision.
This tool is built for quick everyday math. It can help with shopping, invoices, schoolwork, reports, and checking manual calculations.
What is the best way to use the Percentage Calculator?
Enter the values carefully, review the units, and use the result as a reliable reference point. The Percentage Calculator is most useful when you compare scenarios or repeat the calculation with consistent inputs.
Is the Percentage Calculator accurate?
The calculator follows standard calculation logic, but accuracy depends on the values you enter and the assumptions behind the formula. For important math decisions, use it as guidance and verify the result with a trusted source.
Understanding percentage calculations
A percentage is a way of expressing a number as a fraction of 100. The word "percent" comes from the Latin "per centum" meaning "by the hundred." Percentages are used in virtually every area of daily life — from discounts and tax rates to exam scores, interest rates, and health statistics.
The four most common percentage calculations
1. What is X% of Y? (Finding a percentage of a number)
Formula: Result = (X ÷ 100) × Y
Example: What is 15% of $2,400? = (15 ÷ 100) × 2,400 = $360
2. X is what percent of Y? (Finding what percentage one number is of another)
Formula: Percentage = (X ÷ Y) × 100
Example: 45 is what percent of 180? = (45 ÷ 180) × 100 = 25%
3. Percentage increase
Formula: % Increase = [(New Value – Old Value) ÷ Old Value] × 100
Example: Price increased from $800 to $920: = [(920 – 800) ÷ 800] × 100 = 15% increase
4. Percentage decrease
Formula: % Decrease = [(Old Value – New Value) ÷ Old Value] × 100
Example: Salary reduced from $50,000 to $45,000: = [(50,000 – 45,000) ÷ 50,000] × 100 = 10% decrease
Real-world percentage examples
- Shopping discount: A $3,500 jacket with a 30% discount: Discount = $1,050. Final price = $2,450
- Salary hike: Monthly salary of $40,000 with a 12% increment: New salary = 40,000 × 1.12 = $44,800
- GST calculation: Product at $5,000 with 18% GST: GST amount = $900. Total price = $5,900
- Exam score: Scored 68 out of 80: Percentage = (68 ÷ 80) × 100 = 85%
- Weight loss: Starting weight 90 kg, current weight 81 kg: % lost = (9 ÷ 90) × 100 = 10%
Percentage points vs percentage change
This is one of the most commonly misunderstood concepts in percentage calculations. If an interest rate rises from 5% to 8%, it has increased by 3 percentage points — but by 60% in relative terms (since 3 is 60% of 5). In financial news and economic reporting, always clarify which measure is being used.
Successive discounts — a common trap
Two successive discounts of 20% and 10% do NOT equal a 30% total discount. On $1,000: After 20% off = $800. After 10% off $800 = $720. Total discount = $280 on $1,000 = 28% total, not 30%.
Successive percentage changes must be applied sequentially, not added. The formula for the combined effect of two successive percentage changes (a% then b%) is: Combined = a + b + (a × b ÷ 100)
Frequently asked questions about percentages
How do I calculate 20% of a number quickly? Divide by 10 (to get 10%) then double it. For $450: 10% = $45, so 20% = $90.
How do I find the original price before a discount? Divide the discounted price by (1 – discount rate). If an item costs $680 after a 15% discount: Original = $680 ÷ 0.85 = $800.
What is the percentage difference between two numbers? Use the percentage change formula. The direction matters — always use the original (starting) value as the denominator.
Is percentage the same as percentile? No. Percentage is a proportion out of 100. Percentile is a ranking position — the 90th percentile means you scored higher than 90% of the group.