Free Percentage Calculator
Use any of the tools below to quickly solve common percentage math problems for shopping, budgeting, school, analytics, and planning.
1) What is X% of Y?
Example: What is 15% of 240?
2) A is what percent of B?
Example: 30 is what percent of 120?
3) Percentage increase or decrease
Example: from 80 to 100 is a 25% increase.
4) Add or subtract a percentage
Example: Increase 250 by 12% or decrease 250 by 12%.
Why a good percentage calculator matters
Percentages are everywhere. You use them when checking discounts, reviewing tax rates, understanding credit card interest, tracking investment returns, and even reading nutrition labels. A reliable percentage calculator saves time and prevents expensive mistakes, especially when you need quick decisions.
This page gives you four practical tools in one place so you can solve the most common percentage problems without memorizing every formula.
How to use each calculator quickly
Find X% of Y
Enter the percentage in the first box and the number in the second box. This is perfect for finding tips, discounts, and commissions.
- Tip calculation: 18% of a $65 bill
- Sale price reduction: 30% of a $120 jacket
- Tax estimate: 7.5% of a purchase total
Find what percent A is of B
Use this when you have two values and want the percentage relationship. It is useful for grades, completion rates, and performance metrics.
- Grades: 42 correct answers out of 50 questions
- Project progress: 18 tasks done out of 30
- Budget usage: $760 spent out of $1,000
Calculate percentage change
Enter the old value and the new value to measure growth or decline. The result clearly shows whether the change is an increase or decrease.
- Salary growth: from $52,000 to $57,200
- Traffic changes: from 14,000 visits to 11,200 visits
- Price movement: from $3.20 to $2.88
Add or subtract a percentage
Pick a base number, choose a percentage, then choose increase or decrease. Great for setting markups, markdowns, and target budgets.
Core percentage formulas (simple reference)
- X% of Y = (X ÷ 100) × Y
- A is what percent of B = (A ÷ B) × 100
- Percent change = ((New − Old) ÷ Old) × 100
- Increase by X% = Base × (1 + X ÷ 100)
- Decrease by X% = Base × (1 − X ÷ 100)
Even if you know these formulas, using a calculator reduces manual arithmetic errors and speeds up repetitive work.
Common real-world percentage use cases
Shopping and personal finance
Quickly find discount amounts, final sale prices, sales tax, and gratuity. If your savings goal is to cut spending by 12%, you can estimate your new monthly target in seconds.
Business and marketing
Teams often track conversion rate, growth rate, churn rate, and margin changes. Percentage calculators help standardize reporting and reduce confusion across departments.
Education
Students and teachers use percentages for test scores, attendance, and assignment completion. Simple calculations become easier to verify before submitting grades.
Mistakes people make with percentages
- Confusing percentage points with percent change.
- Using the wrong baseline when measuring increases or decreases.
- Forgetting that a value cannot be divided by zero.
- Assuming two opposite percentage changes cancel out (they usually do not).
Quick example
If something goes up 25% and then down 25%, it does not return to the original value. Starting at 100: up 25% gives 125; down 25% gives 93.75. The base changed, so the math changed.
Final thoughts
If you need to get a percentage calculator that is fast, clear, and practical, this page is designed for exactly that. Try each calculator above, test your own numbers, and use the formula section as a quick learning guide.