Fazley RabbiUnit economics is the money story of a single unit of your business: one order, one product or one customer. It asks a simple question: when you make one more sale, do you end up with more money or less? If each unit earns more than it costs to make, deliver and win, growth makes the business stronger. If each unit loses money, growth only makes the losses bigger, however busy the business looks.
Three numbers carry most of the story: margin, customer acquisition cost (CAC) and customer lifetime value (LTV). You do not need an accountant's training to understand them, but you do need honest records.
Start by defining the unit
Before any formula, decide what "one unit" means for you. For an online clothing seller it is usually one order. For a coaching centre it may be one student for one term. For a software business it is one paying account per month. For a wholesaler it might be one carton.
Pick the thing your customers actually pay for. Everything else is measured against it.
Margin: what one sale leaves behind
Gross margin is the selling price minus the direct cost of the item you sold. If you buy a shirt from a supplier and sell it, the gap between the two prices is your gross margin.
That number flatters most small businesses, because many costs sit between the supplier and the customer. Contribution margin is more useful. It subtracts every cost that rises with each extra sale:
- product or raw material cost
- packaging
- delivery charges you pay and do not pass on
- payment fees, such as charges on bKash, Nagad or card payments
- the cost of returns and cancelled cash-on-delivery orders, spread across the orders that succeed
- sales commission, if you pay one per sale
What remains is what one sale contributes towards rent, salaries, electricity and, eventually, profit. A shop with a healthy-looking markup can still have a thin contribution margin once returns and delivery are counted honestly.
Customer acquisition cost: what it takes to win a buyer
CAC is how much you spend to win one new customer. The simple formula:
CAC = total sales and marketing spend in a period ÷ number of new customers won in that period
Include ad spend, boosted posts, influencer fees, the part of staff salaries spent on selling, and marketing tools. Count only new customers, not repeat buyers, or the number will look better than it is.
For example, a home décor page in Sylhet that runs Facebook ads for a month should divide that month's ad spend and the page manager's time by the number of first-time buyers that month, not by every order.
CAC also changes by channel. Customers who arrive through referrals or Google searches often cost less to win than those from cold ads, so work out CAC separately for your main channels when you can.
Lifetime value: what a customer is worth over time
LTV estimates the total contribution margin a customer brings over their whole relationship with you. A simple version:
LTV = contribution margin per order × average number of orders per customer
Notice that it uses margin, not revenue. A customer who spends a lot, but only on heavily discounted items, may be worth less than a quieter one who buys at full price.
If your business is new, you will not yet know how often customers come back. Use a cautious guess, label it as a guess, and update it every few months as real data arrives. A pharmacy or grocery sees many repeat purchases; a furniture shop may sell to each customer once in several years. Both can work, but they can afford very different acquisition budgets.
How the three fit together
| Measure | Question it answers | Watch out for |
|---|---|---|
| Contribution margin | Does one sale make money after its direct costs? | Forgetting returns, delivery and payment fees |
| CAC | What does it cost to win one new customer? | Counting repeat orders as new customers |
| LTV | How much margin does a customer bring over time? | Using revenue instead of margin, or hopeful repeat rates |
The core test: LTV must be comfortably larger than CAC, and you must earn the CAC back fast enough that you do not run out of cash while waiting. A business that only recovers its acquisition cost on a customer's fourth order needs enough cash to survive until that fourth order arrives. That is why unit economics and cash flow are so closely linked.
If LTV is below CAC, you have three levers: raise contribution margin (better prices, lower costs, fewer returns), lower CAC (better targeting, referrals, organic content) or raise repeat purchases (follow-up, better service, reasons to return).
Common mistakes
- Averages that hide problems. One product line may be carrying the others. Work out margin per product where you can.
- Ignoring cash-on-delivery losses. Failed deliveries still cost courier charges and staff time. The page on measuring ad profit after COD returns covers this in detail.
- Treating a discount as only a marketing cost. A discount lowers the margin on every order it touches.
- Calculating once and forgetting. Ad costs, supplier prices and delivery charges move. Recheck every month or quarter.
A first exercise
- Choose your unit, and take last month as the period.
- List every cost that rose with each sale, and calculate contribution margin per unit.
- Add up sales and marketing spend, and divide it by new customers to get CAC.
- Make a cautious estimate of repeat orders, and calculate LTV.
- Compare LTV with CAC, and write down which of the three levers you will work on first.
If you want these numbers on one screen every week, a simple KPI dashboard helps. Help with this kind of analysis is part of my business development work.