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Master percentage calculations for everyday life — discounts, tax, tip, salary increase, compound growth, and more. Includes formulas, examples, and shortcuts.
Everything you need to know
Percentages appear everywhere — calculating a 30% discount at a sale, figuring out a 20% tip, understanding that your salary increased by 8%, or knowing that inflation at 6% reduced your savings' real value. Mastering percentage calculations saves you money and helps you make better financial decisions daily.
Skip the Math: Use our free Percentage Calculator for instant calculations without any formulas.
Answer = (X / 100) × Y
Example: What is 20% of $350? = (20/100) × 350 = 0.20 × 350 = $70
Real use: Calculating a tip or discount amount.
Percentage = (X / Y) × 100
Example: 45 is what percent of 180? = (45/180) × 100 = 0.25 × 100 = 25%
Real use: Test scores, budget tracking ("I spent 35% of my income on housing").
% Change = [(New Value - Old Value) / Old Value] × 100
Example: Your salary went from $65,000 to $71,500. What's the percentage increase? = [(71,500 - 65,000) / 65,000] × 100 = [6,500 / 65,000] × 100 = 10%
Real use: Salary increases, investment returns, price changes.
Original Value = Final Value / (1 + percentage/100)
Example: A jacket costs $84 after a 30% discount. What was the original price? = $84 / (1 - 0.30) = $84 / 0.70 = $120
Real use: Working backwards from sale prices or tax-inclusive prices.
The 10% shortcut: Move the decimal one place left
The 5% shortcut: Take half of 10%
The 1% shortcut: Move decimal two places left
Quick mental math: 18% tip on $80? = 10%($8) + 5%($4) + 3%(~$2.40) ≈ $14.40