Percentage Calculator
Use this calculator to solve the most common percentage problems in seconds: percent of a number, what percent one number is of another, percent change, and adding/subtracting percentages.
What Is a Percentage?
A percentage is a way to express a number as a fraction of 100. The symbol % literally means “per hundred.” For example, 25% means 25 out of 100, which is the same as 0.25 in decimal form or 1/4 as a fraction.
Percentages are used everywhere: discounts in shopping, tax rates, test scores, business growth, interest rates, nutrition labels, and financial reports. Learning how to calculate percentages quickly can save money and improve decisions.
How to Use This Percentage Calculator
1) What is X% of Y?
Use this when you want to find a portion of a number. Example: What is 15% of 240? Enter X = 15 and Y = 240.
2) X is what percent of Y?
Use this when you know the part and the whole. Example: 45 is what percent of 60? Enter X = 45 and Y = 60.
3) Percentage change from A to B
Use this to measure increase or decrease over time. Example: if a price rises from 80 to 92, the calculator shows the percentage increase.
4) Add or subtract a percentage
Use this for things like adding sales tax, applying a tip, or reducing a value by a discount. Enter your base number, percentage, and choose add/subtract.
Percentage Formula Cheat Sheet
- Percent of a number: Result = (X ÷ 100) × Y
- What percent: Percent = (Part ÷ Whole) × 100
- Percentage change: ((New − Original) ÷ Original) × 100
- Add percentage: New Value = Base × (1 + X/100)
- Subtract percentage: New Value = Base × (1 − X/100)
Worked Examples
Example 1: Shopping discount
A jacket costs $120 and is marked 30% off.
- Discount amount = 30% of 120 = 36
- Sale price = 120 − 36 = 84
You pay $84.
Example 2: Test score percentage
You got 42 correct answers out of 50 questions.
- Percent score = (42 ÷ 50) × 100 = 84%
Your score is 84%.
Example 3: Salary increase
Your salary moved from 58,000 to 61,480.
- Difference = 61,480 − 58,000 = 3,480
- Percent increase = (3,480 ÷ 58,000) × 100 = 6%
Your salary increased by 6%.
Common Percentage Mistakes to Avoid
- Mixing up part and whole: In “X is what percent of Y,” Y must be the whole.
- Forgetting divide-by-100: 15% is 0.15, not 15.
- Using wrong base in percent change: Always divide by the original value.
- Applying percentages in the wrong order: Two sequential percentage changes are not simple addition/subtraction.
Where Percentage Skills Help Most
- Personal finance: budgeting, loan rates, investment growth, inflation
- Work and business: KPI improvements, conversion rates, profit margins
- School: grades, score analysis, data interpretation
- Everyday life: restaurant tips, retail discounts, tax calculations
Quick FAQ
Can percentages be negative?
Yes. A negative percentage usually means a decrease or loss.
What if the original value is zero in percent change?
Standard percent change is undefined because division by zero is not allowed. In that case, report absolute change instead.
How many decimal places should I use?
For daily use, 1–2 decimals are usually enough. For technical or financial reporting, you may need more precision depending on context.
Final Takeaway
If you understand a few core formulas, percentage math becomes simple. Use the calculator above whenever you need speed, then review the steps shown in the result area to build confidence. Over time, these calculations become second nature.