How do I calculate what percentage one number is of another?

Use the formula: (Part ÷ Whole) × 100. For example, to find what percentage 25 is of 100: (25 ÷ 100) × 100 = 25%. This is useful for calculating test scores, completion rates, and comparing values in business and academic contexts.

How do I calculate percentage increase and decrease?

For increase: ((New Value - Original Value) ÷ Original Value) × 100. For decrease, the result will be negative. Example: price goes from $50 to $60, that's ((60-50) ÷ 50) × 100 = 20% increase. Essential for tracking price changes, salary raises, and investment returns.

What is the fastest way to calculate tips at restaurants?

For 15% tip: move decimal point one place left and add half that amount. For $40 bill: 10% = $4, half of $4 = $2, so 15% = $6. For 20% tip: double the 10% amount. These mental math tricks work great when you don't have a calculator handy.

How do I calculate discounts and sale prices?

For a 30% discount on $100 item: $100 × 0.30 = $30 discount, final price = $100 - $30 = $70. Or directly: $100 × 0.70 = $70. Always verify sale prices at checkout - sometimes additional discounts apply or exclusions exist.

How do compound percentages work in investments?

Compound percentages multiply each period. 10% annual return for 3 years: Year 1: $1000 × 1.10 = $1100, Year 2: $1100 × 1.10 = $1210, Year 3: $1210 × 1.10 = $1331. Total return is 33.1%, not 30%. This is why starting early makes huge differences in retirement savings.

What are basis points and how do they relate to percentages?

One basis point equals 0.01% or 1/100th of a percent. Used in finance for small changes. 100 basis points = 1%. If interest rates rise from 3.25% to 3.50%, that's a 25 basis point increase. Common in mortgage rates, bond yields, and investment fees.

How do I calculate percentage change between negative numbers?

Use the same formula but be careful with interpretation. From -$10 loss to -$5 loss: ((-5 - (-10)) ÷ (-10)) × 100 = 50% improvement (reduction in loss). However, going from -$10 to +$5 is often described as "turning profitable" rather than a percentage change.

How do I convert fractions and decimals to percentages?

Multiply by 100 and add % symbol. Fraction: 3/4 = 0.75 = 75%. Decimal: 0.125 = 12.5%. To go backwards: 85% = 0.85 = 17/20. These conversions are essential for understanding proportions, probabilities, and statistical data in everyday situations.

What is the difference between percentage point and percent change?

Percentage points measure absolute difference between percentages. If unemployment goes from 5% to 7%, that's 2 percentage points or 40% relative increase ((7-5)/5 × 100). Media often confuses these - always clarify which is being used for accurate understanding of statistics.

How do I calculate weighted percentages and averages?

Multiply each percentage by its weight, sum results, divide by total weights. Test scores: 80% (weight 3) + 90% (weight 2) = (80×3 + 90×2) ÷ (3+2) = 420 ÷ 5 = 84%. Common in grades, portfolio allocations, and survey analysis where some data points matter more than others.

Percentage Calculator

Calculate percentages, percentage increase/decrease, tips, discounts, and more with our comprehensive percentage calculator.

Calculation Type

What is X% of Y?

Percentage (%)

Of Number

Common Uses

Tips & Service

• 15% tip on restaurant bill
• 20% tip for good service
• Service charge calculations

Shopping & Sales

• Discount percentages
• Sale price calculations
• Tax calculations

Finance

• Interest rate calculations
• Investment returns
• Loan percentage rates

Statistics

• Grade percentages
• Data analysis
• Survey results