Calculate a percentage of a number
Example: What is 20% of $500?
%
$
Calculation Result
0.00
Results are estimates. Not professional advice.
Common Percentage Calculations
Calculating Tips
To calculate a tip, multiply the bill amount by the tip percentage divided by 100. For example, an 18% tip on $87.50: 0.18 × $87.50 = $15.75.
Calculating Discounts
For a 30% discount on $120: discount = 0.30 × $120 = $36. Sale price = $120 - $36 = $84.
Calculating Percentage Increase
Formula: ((New Value - Old Value) ÷ Old Value) × 100. Example: salary increase from $52,000 to $57,200 = ((57,200 - 52,000) ÷ 52,000) × 100 = 10% increase.
Quick Mental Math Shortcuts
- 10%: Move decimal one place left (10% of $50 = $5)
- 5%: Find 10% then halve it (5% of $50 = $2.50)
- 20%: Find 10% then double it (20% of $50 = $10)
- 50%: Divide by 2 (50% of $60 = $30)
- 25%: Divide by 4 (25% of $100 = $25)
Frequently Asked Questions
How do I calculate percentage?
Percentage = (Part ÷ Whole) × 100. For example, 25 out of 100 = (25/100) × 100 = 25%.
How do I calculate percentage increase or decrease?
Use: ((New Value - Old Value) ÷ Old Value) × 100. If positive, it's an increase; if negative, it's a decrease.
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