Percentage Calculator
Calculate percentages with ease. Perfect for discounts, tips, grades, statistics, and everyday math.
Understanding Percentages
A percentage is a way of expressing a number as a fraction of 100. The word "percent" means "per hundred." Percentages are used everywhere in daily life - from calculating discounts and tips to understanding statistics and financial data.
Common Percentage Calculations
1. Calculate X% of Y (Percentage of a Number)
Formula: (X ÷ 100) × Y
Examples:
- 15% of 200 = (15 ÷ 100) × 200 = 30
- 25% tip on a $80 bill = (25 ÷ 100) × 80 = $20
- 30% discount on $150 item = (30 ÷ 100) × 150 = $45 off
2. X is What % of Y?
Formula: (X ÷ Y) × 100
Examples:
- 45 is what % of 180? = (45 ÷ 180) × 100 = 25%
- Scored 85/100 on test = (85 ÷ 100) × 100 = 85%
- $40 of $200 budget = (40 ÷ 200) × 100 = 20%
3. X is Y% of What Number?
Formula: (X × 100) ÷ Y
Examples:
- 60 is 30% of what? = (60 × 100) ÷ 30 = 200
- $15 tip is 20% of what bill? = (15 × 100) ÷ 20 = $75
- 18 students is 15% of what class? = (18 × 100) ÷ 15 = 120 students
4. Percentage Increase/Decrease
Formula: ((New Value - Original Value) ÷ Original Value) × 100
Examples:
- From $50 to $65 = ((65-50) ÷ 50) × 100 = +30% increase
- From 200 to 150 = ((150-200) ÷ 200) × 100 = -25% decrease
- Price rose from $80 to $100 = ((100-80) ÷ 80) × 100 = +25%
Practical Applications
Shopping & Discounts
- Calculate sale price: $100 item with 30% off = $100 - ($100 × 0.30) = $70
- Compare discounts: 25% off $80 vs $15 off $75 - which is better?
- Sales tax: Add 8% tax to $50 purchase = $50 × 1.08 = $54
Finance & Money
- Interest rates: Calculate interest earned or owed
- Investment returns: Track portfolio performance
- Budget tracking: What % of income goes to rent?
- Commission: Calculate sales commissions and bonuses
School & Grades
- Test scores: Convert points to percentage grades
- GPA calculations: Determine academic standing
- Attendance: Calculate attendance percentage
Business & Analytics
- Growth rates: Year-over-year revenue increase
- Conversion rates: Website visitors to customers
- Market share: Company's share of total market
- Profit margins: Calculate gross and net margins
Quick Percentage Tips
- 50% = half: Divide by 2
- 25% = quarter: Divide by 4
- 10% is easy: Move decimal one place left (10% of 80 = 8)
- 5% = half of 10%: Find 10%, then divide by 2
- 1% = 1/100: Move decimal two places left
- To add 15%: Multiply by 1.15
- To subtract 20%: Multiply by 0.80
Frequently Asked Questions
How do I calculate a discount percentage?
To find discount amount: multiply the original price by the discount percentage (as a decimal). For example, 20% off $50 = $50 × 0.20 = $10 discount. Final price = $50 - $10 = $40.
What's the difference between percentage increase and percentage point increase?
Percentage increase is relative to the original value. If something goes from 20% to 25%, that's a 5 percentage point increase, but a 25% relative increase ((25-20)/20 × 100).
How do I convert a fraction to a percentage?
Divide the numerator by the denominator and multiply by 100. For example: 3/4 = 0.75 × 100 = 75%. Or simply: (3 ÷ 4) × 100 = 75%.
How do I calculate percentage change over multiple periods?
For compound changes, multiply the change factors: From 100 to 120 (+20%) to 150 (+25% of 120). Total change: ((150-100)/100) × 100 = 50% total increase.
Why doesn't a 50% increase followed by a 50% decrease return to the original?
Because percentages are relative to different base values. Starting at 100: +50% = 150, then -50% of 150 = 75, not 100. The decrease is calculated on the new, higher value.
How do I calculate what percentage one number is of another?
Divide the part by the whole and multiply by 100. Formula: (Part ÷ Whole) × 100. Example: 30 is what % of 150? (30 ÷ 150) × 100 = 20%.
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Aggiornato Febbraio 2026 · Testati e verificati
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