Standard tipping in the US: 18-20% for sit-down restaurants, 15-18% for counter service with table delivery, 10-15% for takeout/counter pickup, $1-$2 per drink at bars, 15-20% for hair salons and spas. For exceptional service, 25%+ is appropriate. Tip on the pre-tax amount. Many restaurants now suggest 20-25-30% on tablets — choose what fits the service level.

Gross profit margin = (Revenue - Cost of Goods Sold) ÷ Revenue × 100. Net profit margin = (Revenue - All Expenses) ÷ Revenue × 100. For example, if you sell a product for $100, it costs $40 to make, and you have $30 in other expenses: gross margin = 60%, net margin = 30%. Healthy margins vary by industry — retail averages 3-5% net, software 20-30%, consulting 15-25%.

Markup is the percentage added to cost to get selling price. Margin is the percentage of selling price that is profit. They use different denominators: Markup = (Price - Cost) ÷ Cost × 100. Margin = (Price - Cost) ÷ Price × 100. Example: cost $60, price $100 → markup is 66.7%, but margin is 40%. A common mistake is confusing the two — a 50% markup only gives you a 33% margin.

At 3% annual inflation, your money loses about half its purchasing power in 24 years. A $50,000 salary today would need to be $67,000 in 10 years to maintain the same standard of living. To protect against inflation: invest in assets that historically outpace inflation (stocks average 7-10%/year), consider I-bonds or TIPS, negotiate annual raises of at least 3-4%, and avoid holding too much cash.

Multiply your hourly rate by 2,080 (40 hours × 52 weeks) for a standard full-time salary. For example: $25/hour = $52,000/year. Quick mental math: double your hourly rate and add three zeros ($25 → $50,000 — close enough for estimates). Remember to account for unpaid time off, benefits value, and taxes when comparing hourly vs. salary positions.