Percentage Calculator
Use any tool below to quickly solve common percentage problems.
1) What is X% of Y?
Example: 15% of 240 = 36
2) X is what percent of Y?
Example: 45 is 25% of 180
3) Percent increase or decrease
Example: from 80 to 92 is a 15% increase
4) Add or subtract a percentage
Example: 120 + 10% = 132
Quick answer: how to use percentage on calculator
If your calculator has a % button, percentage math is fast. In many cases, you type: number × percent % for finding a percentage value, or number ± percent % for adding/subtracting percentages.
Examples
- Find 20% of 50: 50 × 20 % → 10
- Add 15% tip to 80: 80 + 15 % → 92
- Subtract 30% discount from 200: 200 - 30 % → 140
Different calculator brands can behave a little differently, so if your answer looks odd, use the universal formula method below.
Understand what percentage means
A percentage is just “per hundred.” So 25% means 25 out of 100, or 0.25 in decimal form. This one idea makes all percentage problems easier:
- Convert percent to decimal by dividing by 100.
- Then multiply or divide depending on the question.
How to do percentage calculations on any calculator
1) Find X% of Y
Formula: (X ÷ 100) × Y
Example: 18% of 250 = (18 ÷ 100) × 250 = 45
2) Find what percent one number is of another
Formula: (Part ÷ Total) × 100
Example: 30 is what percent of 120? (30 ÷ 120) × 100 = 25%
3) Add a percentage
Formula: Original × (1 + percent ÷ 100)
Example: Add 8% tax to 75 → 75 × 1.08 = 81
4) Subtract a percentage
Formula: Original × (1 - percent ÷ 100)
Example: 40% off 90 → 90 × 0.60 = 54
5) Percent change (increase/decrease)
Formula: ((New - Old) ÷ Old) × 100
Example: Price from 50 to 65 → ((65 - 50) ÷ 50) × 100 = 30% increase
Using the % button correctly
On most standard calculators, the % key treats the entered percent as a fraction of the number already on screen. That is why 200 + 10% usually gives 220 and 200 - 10% gives 180.
- Good for: tax, tips, discounts, markups.
- Potential issue: scientific and app calculators may interpret % differently.
If unsure, use the formula method to avoid mistakes.
Real-world examples
Sales discount
A jacket costs $120 with a 25% discount. Discount = 120 × 0.25 = $30. Final price = 120 - 30 = $90.
Restaurant tip
Bill is $64, tip is 18%. Tip = 64 × 0.18 = $11.52. Total = 64 + 11.52 = $75.52.
Salary raise
Salary goes from $48,000 to $52,800. Percent increase = ((52,800 - 48,000) ÷ 48,000) × 100 = 10%.
Common mistakes to avoid
- Forgetting to divide by 100 when converting percent to decimal.
- Dividing by the wrong base when finding percent change.
- Applying discounts and taxes in the wrong order.
- Assuming all calculators use the % key the same way.
Fast mental shortcuts
- 10% of a number = move decimal one place left (10% of 250 = 25).
- 1% = divide 10% by 10.
- 5% = half of 10%.
- 15% = 10% + 5%.
These shortcuts help you check your calculator result in seconds.
Final takeaway
To master how to use percentage on calculator, learn two things: the % key behavior on your device and the core formulas. Once you know both, you can handle discounts, tax, tips, growth rates, and percentage comparisons with confidence. Use the calculator tool above whenever you need a quick and accurate result.