01
The busiest shop on the lane
Fiction Meera and Shop No. 14 are invented.
Meera runs a provisions shop in a Delhi market. Business is good. Footfall is up, the new detergent brand is moving, and three housing societies nearby now order by phone. By every measure she can see from behind the counter, the shop is growing.
Then, in the second week of the month, she can’t pay the wholesaler in full. Nothing has gone wrong. No theft, no slump, no disaster. Her own notebook says she made a profit last month and will make a bigger one this month.
What happened is ordinary. To sell more, she bought more stock — and paid for it upfront. To keep the housing societies happy, she let them settle at month-end — so a chunk of her sales became promises rather than notes in the drawer. Rent, wages and electricity arrived on schedule regardless. Profit is a story about whether the business earns more than it spends over a period. Cash is a story about whether there is money in the box today. A growing shop can win the first story and lose the second.
Sales measure activity. Profit measures whether that activity is worth doing. Cash measures whether you can keep doing it.
Families who have run shops often know this in their bones without having names for it. This page gives it names and numbers — not to turn a shop into a spreadsheet, but so that the owner, the people who work there and the customers who depend on it are not ambushed by arithmetic.
Context The author grew up around family retail. That exposure shaped the questions here, but no real ledgers, incomes or shop results are used or described; all examples are constructed.
The three calculators
Each calculator below opens with fictional defaults. Change any number and the results update. Formulas and a worked example sit under each one. Educational approximation, not business advice. Use prices without GST: GST collected is owed to the government and is not the shop’s revenue.
02
Markup is not margin
Established framework
Buy a packet for ₹80, sell it for ₹100. You made ₹20. Is that 25% or 20%? Both — it depends on what you divide by.
- Markup divides the ₹20 by the cost: 20 ÷ 80 = 25%.
- Gross margin divides the ₹20 by the selling price: 20 ÷ 100 = 20%.
The confusion is expensive in one direction only. If someone says “we need a 25% margin” and you add 25% to cost, you get ₹100 — a 20% margin. To truly earn 25% of the selling price on an ₹80 item, the price must be 80 ÷ (1 − 0.25) = ₹106.67. Margin can never reach 100% (the item would have to cost nothing); markup has no ceiling at all. That asymmetry is why margin is the safer number to plan with: it tells you how much of every rupee that comes in is left to pay for everything else.
03
The rent doesn’t care how busy you were
Established framework Cost-volume-profit analysis
Some costs move with every sale: the cost of the goods themselves, a carry bag, a card-payment fee. These are variable costs. Others arrive every month whether you sell ten units or ten thousand: rent, salaries, electricity, the accountant. These are fixed costs — fixed over a normal range of activity, not forever.
What each sale leaves behind after its own variable cost is its contribution: the amount it contributes towards the fixed costs. Sell a ₹100 item with ₹70 of variable cost and each sale contributes ₹30. If fixed costs are ₹45,000 a month, the shop needs 45,000 ÷ 30 = 1,500 units just to stand still. Open 26 days a month, that is roughly 58 units a day before the first rupee of profit.
The most common hidden error is leaving the owner out. If the owner works full days and takes nothing from the shop until “profit”, their labour is a cost the model doesn’t see. Add a modest ₹30,000 monthly draw to the fixed costs above and break-even jumps from 1,500 to 2,500 units. Interpretation Many shops that “just about break even” are quietly being subsidised by an unpaid family member.
04
Money that sits on shelves
Established framework Illustration
Stock is cash wearing a disguise. Every packet on the shelf is money that was paid out and has not yet come back. That is not bad — an empty shop sells nothing — but it means the speed at which stock turns into sales matters as much as the margin on it.
Accountants measure that speed with inventory turnover: cost of goods sold in a year divided by the average value of stock held. Divide 365 by turnover and you get days of inventory — roughly how long an average rupee of stock waits before it is sold.
Worked example Fiction
| Cost of goods sold in the year | ₹18,00,000 |
|---|---|
| Stock at start / end of year | ₹2,00,000 / ₹4,00,000 |
| Average stock | (2,00,000 + 4,00,000) ÷ 2 = ₹3,00,000 |
| Turnover | 18,00,000 ÷ 3,00,000 = 6 times a year |
| Days of inventory | 365 ÷ 6 ≈ 61 days |
If the same sales could be supported with ₹1,50,000 of average stock, turnover doubles to 12 and days fall to about 30. Same sales, same margin — and ₹1,50,000 of cash released from the shelves.
Two cautions. First, an average hides the shape: a shop can have fast-moving rice and dal alongside a back shelf of slow items bought on a hunch three years ago. Turnover by category is far more useful than one number. Second, higher turnover is not always better. Run stock too lean and customers find gaps, walk to the next shop and — this is the part no ratio shows — may not come back. Interpretation The goal is not minimum stock; it is stock that earns its shelf space.
05
Why profit is not cash
Established framework Accrual accounting and the cash conversion cycle
Profit is counted when a sale happens and matched with the cost of the goods sold. Cash is counted when money actually changes hands. Between those two moments, rupees can be in three places that are not the cash box:
- On the shelf as inventory you have paid for but not yet sold.
- In customers’ pockets as receivables — the khata, the month-end account, the “I’ll pay you Monday”.
- And in the opposite direction, in your pocket but owed to suppliers as payables — goods received on credit.
That gives a reconciliation every owner can memorise:
Change in cash = Profit − increase in stock − increase in money owed to you + increase in money you owe
(Real statements add more lines — loans, equipment, depreciation, tax, the owner’s withdrawals — but for day-to-day trading these four carry most of the story.) The same idea, expressed in days, is the cash conversion cycle: days of inventory + days customers take to pay − days you take to pay suppliers. If stock waits 61 days, customers take 20 and suppliers give you 15, every rupee you put into stock is away for about 66 days. Growth makes that hole bigger, because more sales need more stock and more credit before they bring cash back.
Things to try: set “You pay suppliers after” to 1 month and watch the crunch disappear. Set growth to 0% and the crunch eases too — Interpretation which is why fast growth, not slow trade, is often what stretches a small shop’s cash.
06
The arithmetic of a discount
Established framework Contribution and price elasticity
A 10% discount sounds like it costs 10% of profit. It usually costs far more, because the discount comes entirely out of the margin. On a ₹100 item with ₹70 of variable cost, contribution is ₹30. Cut the price to ₹90 and contribution falls to ₹20 — a third of the contribution gone for a tenth of the price. To earn the same total contribution, the shop must sell 50% more units (30 ÷ 20 = 1.5).
Run the logic the other way and price rises look less frightening than they feel. At a 30% contribution margin, a 5% increase means the shop could lose up to about 14% of its unit sales and still earn the same contribution. Whether customers actually leave depends on price elasticity — how strongly quantity bought responds to price — which differs by product, neighbourhood, competition and season, and which no calculator on this page can know for you.
Interpretation Discounts are not always wrong. They can clear stock before it expires, win a customer whose later purchases carry better margins, or match a competitor when walking away would cost more. The point is to know the price of the discount before offering it — and to notice that “we’re busier than ever” is exactly what a too-generous discount feels like from the inside.
07
Three stories, three cash leaks
Fiction All three shops and every figure are invented. Arithmetic is real.
1 · The festive discount
Arjun runs a small household-goods shop: average price ₹100, variable cost ₹70, fixed costs ₹45,000 a month. He usually sells 2,000 units and earns about ₹15,000. Before the festival he puts up a banner: 10% off everything. The shop is packed. He sells 2,000 units — the same as usual, because his regular customers simply bought at the lower price.
Contribution per unit fell from ₹30 to ₹20, so 2,000 units now contribute ₹40,000 against ₹45,000 of fixed costs: a ₹5,000 loss in his best-feeling month of the year. Break-even rose from 1,500 to 2,250 units. To match his usual ₹15,000, he needed 3,000 units — 50% more.
Lesson: a discount must be judged against the extra units it brings, not the crowd it draws.
2 · The bulk-buy bargain
A wholesaler offers Farida 4% off if she buys three months of a ₹50 item at once instead of monthly. She sells 400 a month. Monthly buying costs ₹20,000 each month; the bulk deal costs 1,200 × ₹48 = ₹57,600 today. Saving: ₹2,400.
The catch is timing. In month 1 she has paid ₹37,600 more than usual; by month 2, ₹17,600 more; only in month 3 does she come out ₹2,400 ahead. If that money had to be borrowed at a hypothetical 1.5% a month, the interest is roughly ₹564 + ₹264 ≈ ₹830 — so the deal still wins on paper. What the paper misses: the ₹37,600 she couldn’t spend on faster-moving items in month 1, the risk that sales slow to 300 a month (stretching the stock to four months), and expiry dates. Interpretation Bulk deals are often good. They are rarely free.
Lesson: a discount on purchases is paid for with cash today and risk tomorrow.
3 · The generous khata
Kabir’s shop sells ₹3,00,000 a month at a 20% gross margin. About 20% of sales are on credit, settled within a month and a half. To keep up with a new competitor, he lets more regulars buy on account: credit rises to 50% of sales. Nothing else changes.
Money waiting in the khata rises from about 20% × ₹3,00,000 × 1.5 = ₹90,000 to 50% × ₹3,00,000 × 1.5 = ₹2,25,000. His profit is unchanged, but ₹1,35,000 more of his cash now lives in other people’s homes. If even 2% of credit sales are never paid, that is ₹3,000 a month — about 5% of his ₹60,000 monthly gross profit, gone quietly.
Lesson: credit is a loan you make to customers. It can build loyalty and serve neighbours who are short this week; it still needs to be financed by someone.
08
Who pays for a thinner margin?
Interpretation Evidence where cited
Every lever on this page moves money between people. A margin is not just a ratio; it is a decision about who absorbs the cost when things are tight. The arithmetic is neutral. The choices are not.
Pay suppliers later
Owner: frees cash instantly — in Calculator 3, it can erase the crunch.
Supplier: becomes the shop’s unpaid lender. If they are a micro or small enterprise, they may have less cushion than the shop.
Worker: indirectly safer, if the alternative was cutting hours.
Evidence In India, Section 15 of the MSMED Act, 2006 caps the time a buyer may take to pay a registered micro or small supplier at 45 days where agreed in writing, or 15 days without an agreement (see sources).
Cut staff costs
Owner: lowers fixed costs and break-even fast.
Worker: carries the whole adjustment — fewer hours, more tasks, less rest.
Customer: longer queues, less help, more mistakes.
A shop whose margin depends on unpaid overtime has a margin problem that has been moved, not solved.
Shrink the pack, keep the price
Owner: protects margin without a visible price rise.
Customer: pays more per gram, often without noticing.
Worker: answers the questions when regulars do notice.
Legal is not the same as trustworthy. In a neighbourhood shop, trust is part of the product.
Stop giving credit
Owner: cash arrives faster; bad-debt risk falls.
Customer: those paid weekly or daily may lose an informal safety net.
Worker: no longer has to chase awkward dues.
Smaller limits, clear dates or deposits are middle paths between “unlimited khata” and none.
Hypothesis A small business that makes these trade-offs explicitly — writing down who bears each cost before deciding — will make fewer choices it later regrets than one that optimises a single number. This is a proposition to test, not a finding.
The International Labour Organization’s idea of decent work — productive employment with rights, social protection and a voice — is a useful reminder that a business’s numbers and its people’s conditions are measured on different ledgers. For a longer argument about not treating people as inventory, see Human Capital for Humans.
09
Objections, limits and myths
The strongest objection
“Shopkeepers have run on instinct and a khata for generations. They know their customers, their suppliers and their stock better than any formula. This is classroom arithmetic for people who don’t stand behind a counter.”
Much of that is right. An experienced owner often carries a remarkably accurate mental model of which items move, who will pay and when to say no. Formulas don’t replace that knowledge; they rarely even capture it. The case for the arithmetic is narrower: Interpretation instinct is calibrated on the past, and it is least reliable exactly when the shop changes — growing quickly, adding a product line, taking on bulk orders, facing a new competitor. Those are the moments when the sense of “we’re doing well” and the cash box can drift apart without anyone noticing until a payment is due.
Where these tools break
- Costs aren’t straight lines. A second helper, a bigger fridge or a new shutter turns “fixed” costs into steps. Break-even only holds within a range.
- Shops sell many things. A shop-wide margin is a weighted average that shifts whenever the mix shifts — sell more low-margin staples and the average falls even if no price changed.
- Seasons and festivals. Monthly averages hide the weeks when stock must be built ahead of demand.
- Shrinkage and expiry. Breakage, theft, spoilage and stale stock are real costs that rarely appear in a back-of-envelope margin.
- Taxes and compliance. GST timing, input credits and income tax change both profit and cash; none are modelled here.
- Counterexample: some businesses are profitable and cash-rich because customers pay before suppliers must be paid — a shop with fast-moving stock and supplier credit can have a negative cash conversion cycle. Profit-not-cash cuts both ways.
Common misconceptions
- “Busy means profitable.”
- Busy means volume. Volume at too thin a contribution can lose money faster.
- “Profit means I can spend it.”
- Only if it has become cash and isn’t already promised to a supplier.
- “A 25% markup is a 25% margin.”
- It is a 20% margin. The denominators differ.
- “More stock is always safer.”
- It is safer for availability and riskier for cash, expiry and storage.
- “Credit customers are just slower customers.”
- They are customers you are financing. Some never pay.
- “Break-even is a target.”
- It is the floor. Owner’s pay, savings and repairs come after it.
10
Before you believe the dashboard
Point-of-sale apps and accounting software produce confident numbers. Before trusting one, check what sits underneath it. Ticking boxes here is session-only: nothing is stored.
0 of 10 checked
11
Glossary
- Markup
- Gross profit as a percentage of cost.
- Gross margin
- Gross profit as a percentage of selling price.
- Variable cost
- A cost that rises with each unit sold (goods, packaging, per-sale fees).
- Fixed cost
- A cost that stays roughly the same each month within a normal range of activity (rent, salaries).
- Contribution
- Price minus variable cost: what each sale adds toward fixed costs and profit.
- Break-even point
- The sales level at which total contribution exactly covers fixed costs.
- Margin of safety
- How far expected sales could fall before reaching break-even.
- Inventory turnover
- Cost of goods sold ÷ average inventory, for a period.
- Days of inventory
- 365 ÷ annual inventory turnover: roughly how long stock waits to be sold.
- Receivables
- Money customers owe the shop for goods already supplied.
- Payables
- Money the shop owes suppliers for goods already received.
- Working capital
- Current assets (cash, stock, receivables) minus current liabilities (payables and other short-term dues): the money tied up in running day to day.
- Cash conversion cycle
- Days of inventory + days to collect − days to pay suppliers.
- Accrual accounting
- Recording revenue and expenses when earned or incurred, not when cash moves.
- Price elasticity of demand
- How strongly the quantity bought responds to a change in price.
- Khata
- An informal running account in which a shop records goods given on credit to regular customers.
12
Sources — what each establishes, and what it doesn’t
Links checked on 24 October 2026. Textbook formulas are standard; the examples, interpretations and hypotheses on this page are the author’s own.
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Franklin, M., Graybeal, P., & Cooper, D. (2019). Principles of Accounting, Volume 2: Managerial Accounting, Ch. 3, “Calculate a Break-Even Point in Units and Dollars”. OpenStax. openstax.org
Establishes: contribution margin, break-even in units and sales, and the assumptions behind them (linear costs, constant price, constant sales mix). Doesn’t: describe Indian retail or say what any real shop’s costs are.
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Franklin, M., Graybeal, P., & Cooper, D. (2019). Principles of Accounting, Volume 1: Financial Accounting, Ch. 16, “Statement of Cash Flows” (key terms). OpenStax. openstax.org
Establishes: how accrual profit differs from cash flow, and the indirect method that reconciles them. Doesn’t: provide the simplified six-month model used here, which is the author’s illustration.
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Shapiro, D., MacDonald, D., & Greenlaw, S. A. (2022). Principles of Microeconomics 3e, Ch. 5, “Elasticity”. OpenStax. openstax.org
Establishes: the concept and measurement of price elasticity of demand. Doesn’t: give elasticities for any product or neighbourhood; the price table above assumes nothing about how customers will actually respond.
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Lok Sabha, Unstarred Question No. 91, “Payment to SMEs by Big Companies”, answered by the Ministry of Finance (25 November 2024). eparlib.sansad.in (PDF)
Establishes: the official statement of Section 15 of the MSMED Act, 2006 — payment to micro and small suppliers within the agreed date, not exceeding 45 days, or 15 days without a written agreement. Doesn’t: apply to a shop’s retail customers, or constitute legal advice on any particular case.
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Marathe, M. M. (2026). “From Delays to Discipline: Unlocking MSME Liquidity through Reforms”. The Chartered Accountant Journal, ICAI. cajournal.icai.org
Establishes: a professional overview of delayed-payment reforms, including Section 43B(h) of the Income-tax Act and the move of new delayed-payment cases to the MSME online dispute resolution portal from 15 October 2025. Doesn’t: serve as primary law; check current official notifications before acting.
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International Labour Organization. “Decent work and the 2030 Agenda for sustainable development” (topic page). ilo.org
Establishes: the ILO’s framing of decent work around employment, rights at work, social protection and social dialogue. Doesn’t: prescribe how a particular small business should set wages or margins.
For longer essays on work, behaviour and everyday decisions, see Sahil’s writing archive on Medium. Essays are opinion and reflection, not scholarly evidence.
An open question
If a shop can stay profitable only by paying its suppliers late, its workers less, or its customers in smaller packets, is it profitable — or is someone else quietly lending it the difference?
There is no formula for that answer. But you can only ask it once you can see where the money actually goes.