📊 How to Calculate Percentage
Percentages show up everywhere — restaurant tips, sales tax, discounts, test scores, salary raises, investment returns. Here are the 4 formulas you'll actually use, with examples.
The basic formula: Percent = (Part ÷ Whole) × 100. Get instant answers with the Percentage Calculator — supports all 4 types.
🎯 The 4 Types of Percentage Problems
Example: What is 15% of $80?
Formula: (X ÷ 100) × Y = $12
Example: 30 is what % of 150?
Formula: (X ÷ Y) × 100 = 20%
Example: $50 → $65
Formula: ((New − Old) ÷ Old) × 100 = 30% increase
Between two numbers, either direction
Formula: |A − B| ÷ ((A+B)÷2) × 100
🧮 Worked Examples (Step-by-Step)
Example 1: Tip Calculation
You want to tip 20% on a $65 bill.
Step 1: 20 ÷ 100 = 0.20
Step 2: 0.20 × 65 = $13 tip
Step 3: $65 + $13 = $78 total
Example 2: Test Score
You got 45 correct out of 50 questions.
Step 1: 45 ÷ 50 = 0.90
Step 2: 0.90 × 100 = 90%
Example 3: Discount Shopping
A $120 jacket is 30% off.
Step 1: 30 ÷ 100 = 0.30
Step 2: 0.30 × 120 = $36 discount
Step 3: $120 − $36 = $84 final price
Example 4: Salary Raise
Your salary went from $60K to $66K.
Step 1: 66,000 − 60,000 = 6,000
Step 2: 6,000 ÷ 60,000 = 0.10
Step 3: 0.10 × 100 = 10% raise
💡 Quick Mental Math Tricks
Move the decimal point one place left. 10% of $45 = $4.50
10% of $45 is $4.50, so 5% = $2.25
For a 20% tip on $45: $4.50 × 2 = $9
On $45: $4.50 + $2.25 = $6.75
📉 Percentage vs Percentage Points
If a mortgage rate goes from 5% to 6%, that's a 1 percentage point increase, but a 20% relative increase (1 ÷ 5 = 0.20). News headlines confuse these constantly.
❓ FAQ
What's the easiest way to calculate percentages?
For 10%: move the decimal one place left. For 5%: half of that. For 15%: add them together. For 20%: double 10%. This covers most everyday situations.
How do I calculate a percentage increase?
Subtract the original from the new value, divide by the original, then multiply by 100. Example: 50 → 65 = (15 ÷ 50) × 100 = 30% increase.
How do I find the original price from a discount?
Divide the sale price by (1 − discount%). Example: $84 is 30% off, so original = $84 ÷ 0.70 = $120.
What's the difference between percent and percentage point?
"Percent" refers to a fraction of 100. "Percentage point" measures the absolute difference between two percentages. 5% → 6% is +1 percentage point (or +20% relative).
Solve Any Percentage Problem
Free calculator with step-by-step solutions for all 4 types.
🧮 Try the Percentage Calculator →