Business math refresher for traders
Margins and markups, discounts, GST, break-even, simple and compound interest, stock turnover, the cash cycle, reordering, average cost and unit prices, with worked examples and quizzes.
A trader lives on thin margins, so small arithmetic mistakes become real losses: a markup mistaken for a margin, GST counted as income, a cash discount skipped when it was worth taking. These pages are a refresher.
Each topic has a plain-words explanation, the standard formulas with their terms, worked examples at three levels (Basic Intermediate Advanced), and a quiz that tells you instantly whether you were right and why.
Every number on these pages is calculated by a script and checked against the page before it is published.
- Margins, markups and discountsMargin and markup are not the same number. Price to a target margin, and see why 10% + 5% is not 15% and when a cash discount is worth borrowing for.6 worked examples · 16 quiz questions
- GST math for tradersInclusive and exclusive prices, taking GST out of an MRP, input tax credit and your net GST payable.3 worked examples · 8 quiz questions
- Break-even for tradersHow many units, or how many rupees of sales, before you start making money; and what a price cut or GST mistake does to that number.5 worked examples · 8 quiz questions
- Simple and compound interestSupplier late-payment charges, short loans in days, compounding frequency, effective annual rate and the rule of 72.7 worked examples · 16 quiz questions
- Stock turnover, holding cost and the cash cycleHow fast your stock moves, what holding it costs, and how inventory, debtor and creditor days add up to your cash conversion cycle.6 worked examples · 14 quiz questions
- Reorder level, order quantity and average costWhen to reorder, how much to order (EOQ, explained simply), and the weighted average cost of stock bought at different prices.7 worked examples · 15 quiz questions
- Unit conversions and per-unit pricesQuintals, tonnes, cases and gross; comparing packs by price per kg or litre; and pricing after loss in handling.3 worked examples · 7 quiz questions
- Mixed quizQuestions across all topics, basic to advanced.12 quiz questions
Related topics on other levels. The same skills carry up the ladder: see dealer business math for schemes, stock financing and showroom returns.
How numbers are rounded on these pages. Calculations are done at full precision and rounded only at the end, half up. Rupee amounts are rounded to the nearest rupee unless shown with paise, in which case to the nearest paisa. Percentages are shown to two decimal places, and days to one decimal place. Break-even quantities and reorder levels are rounded up to the next whole unit, because rounding down would leave you short. Economic order quantity is rounded to the nearest whole unit. Interest for a number of days uses a 365-day year. All examples and quiz questions are Hypothetical: they show the method, not real prices or rates.