Percentage & Ratio Calculator
Calculate percentages, ratios, and proportions with ease
Common Formulas
Percentage Calculations
- X% of Y = (X × Y) ÷ 100
- X is what % of Y? = (X ÷ Y) × 100
- X is Y% of what? = X ÷ (Y ÷ 100)
- Percentage change = ((New - Original) ÷ Original) × 100
Ratio Calculations
- Simplify A:B = (A ÷ GCD):(B ÷ GCD)
- Ratio to decimal = A ÷ B
- Ratio to percentage = (A ÷ B) × 100%
- Proportion A:B = C:D means A ÷ B = C ÷ D
Common Examples
Sales Tax
Item cost: $50
Sales tax: 8%
Tax amount: $50 × 0.08 = $4
Total cost: $50 + $4 = $54
Discount
Original price: $80
Discount: 25%
Discount amount: $80 × 0.25 = $20
Sale price: $80 - $20 = $60
Tip Calculation
Bill amount: $45
Tip percentage: 15%
Tip amount: $45 × 0.15 = $6.75
Total payment: $45 + $6.75 = $51.75