Shopping & Small Business

Markup and margin sound identical but give different prices. Learn the profit margin vs markup formulas, with worked examples in USD, GBP and AUD.

How to calculate a restaurant tip correctly: pre-tax vs post-tax, how to spot auto-gratuity on group bills, and worked examples in USD, GBP and AUD.

Ordering holiday inventory before working out your break-even point can turn a sure sale into a loss. The exact formula, with a worked example.

Stacked store discounts don't add — they multiply. Here's the real math behind 'extra % off' sales, worked through with actual back-to-school numbers.

Etsy fees quietly eat 9–15% of every sale before your own costs. Here's the real math behind Etsy profit margins, worked through with actual numbers.

Splitting group trip costs by headcount rarely comes out fair. The exact math for equal splits, itemized splits and multi-currency trips.