The five numbers that tell you if your store is profitable

Open a typical store owner's laptop and count the tabs: Shopify analytics, a Meta Ads dashboard, a spreadsheet someone built eighteen months ago that nobody quite trusts anymore. Every tab has a number somebody insists matters. Most of them don't move the business at all.

The instinct when a metric feels important is to keep watching it. That instinct is the problem. A finance team tracking fifteen KPIs a day isn't more in control than one tracking five. It's just busier, and slower to notice when something is genuinely wrong, because the signal is buried under noise that looks exactly like signal.

The book behind this kit, 5 Numbers Every E-Commerce CFO Must Know, cuts the picture down to five: gross margin, cash conversion cycle, marketing ROI, inventory turnover, and net profit per order. Not because five is a tidier number than fifteen, but because these five move each other, and a store can act on each one this week.

The five numbers, and where each one comes from

Gross margin is revenue minus cost of goods sold, over revenue, except the book's version of "cost of goods" is wider than most spreadsheets allow. Shipping and fulfillment, returns and refund costs, payment and platform fees, and packaging all belong in the calculation, not just what you paid the supplier. A healthy e-commerce margin runs 40-60%, though the trend matters more than the number itself: a 5-point improvement on $10 million in revenue is $500,000 in additional gross profit, assuming operating costs hold steady. The same 5-point move in the other direction means finding 25% more revenue just to stay where you were.

Cash conversion cycle measures how long your money is tied up between buying inventory and collecting payment: days inventory outstanding, plus days sales outstanding, minus days payables outstanding. A business doing $10 million a year with a 90-day cycle needs roughly $2.5 million in working capital just to keep operating. Trim that to 60 days and over $800,000 comes free: money that was sitting in a warehouse or waiting on a payment processor, now available to fund the next order instead of just the current one.

Marketing ROI, not ROAS, accounts for what a channel actually returns once acquisition cost, lifetime value, and channel-specific contribution margin are in the picture. ROAS answers "how much revenue did this ad generate." Marketing ROI answers the question that determines whether you should spend more: how much of that revenue was profitable, and will the customer still be buying in six months.

Inventory turnover (how many times stock sells and gets replaced in a year) typically runs 4 to 8 times in a healthy operation, tracked at the SKU level rather than as one blended average. An apparel retailer holding $2 million in inventory at 4 turns makes $8 million in sales; push that to 6 turns and $670,000 in cash comes free, without adding a single new customer.

Net profit per order is where the other four numbers actually land. Two identical $100 orders can show the same revenue and opposite outcomes: one clears $24 in profit, the other loses $12, once payment processing, fulfillment, return probability, customer service allocation, and platform fees are attached to that specific transaction rather than averaged across the business. One apparel brand's order-level audit found 35% of its transactions were losing money while its aggregate reporting still showed a healthy margin. Fixing what the audit found lifted net profit per order 28% within six months.

Where people go wrong

The first failure is treating all five numbers as equally urgent every day. They're not. The book's own cadence puts gross margin, cash position, and marketing performance on a daily check; inventory turnover and cash conversion cycle trends on a weekly one; and marketing ROI by channel, cohort performance, and margin trends as a monthly deep dive. Checking all five daily just means checking none of them properly.

The second is chasing ROAS because it updates faster than marketing ROI does. A channel with a strong ROAS and a customer base that only ever buys once is not a good channel. It's a fast way to spend money finding that out.

The third, and most expensive, is measuring without a threshold. A number you glance at but haven't set an action trigger for is decoration, not management. The book's discipline is blunt: define, for each metric, exactly what value makes you act, and act the same week you see it, because a margin problem caught in month one is a pricing fix, and the same problem caught in month six is a cash-flow emergency. The full system for making a store's numbers hold together, not just these five in isolation, is in the e-commerce guide.