This is educational material, not personal financial, tax or legal advice. The numbers in this lesson are made up and are only here so you can practice the math. Talk through your own taxes, contracts and bookkeeping with an accountant or an attorney.
The gist
You can work from morning till night, watch money land in your bank account and still be losing money. It happens when you only look at revenue and don't know how much you actually earn on a single customer.
Unit economics answers two questions:
- How much you earn on one customer after all the costs of serving them.
- How much it costs to bring that customer in.
If the first number is clearly bigger than the second, the business can grow. If it's smaller, every new customer makes you poorer, and advertising only speeds up the slide.
Key terms
| Term | What it means in plain English |
|---|---|
| Revenue per customer | How much a customer pays you |
| Variable costs | What you spend on each customer: materials, delivery, fees, pay-per-use services, your time |
| Margin per customer | Revenue per customer minus variable costs. What you actually keep |
| Customer acquisition cost (CAC) | What it costs to bring in one new customer: ads, back-and-forth messages, free consultations |
| Customer lifetime value (LTV) | How much margin one customer brings you over the whole time they keep buying from you |
You don't need to memorize the abbreviations. You need to be able to work out these five numbers for your own business.
How it works: two everyday examples
Example 1. Custom cakes
Maria bakes cakes at home and sells them through Instagram and Facebook. One cake sells for $50. Sounds decent. Let's break it down.
What goes into each cake:
| Cost | Amount |
|---|---|
| Ingredients | $14 |
| Box and packaging | $3 |
| Delivery | $5 |
| Total variable costs (in cash; we'll count Maria's time below) | $22 |
Margin on one cake: $50 − $22 = $28.
Now her time. One cake takes 3 hours. So an hour of Maria's work brings in $28 ÷ 3 ≈ $9.33. That's the first unpleasant discovery: "a $50 cake" turns into "a job that pays about $9 an hour."
Acquisition cost. In one month Maria spent $60 on social media ads and got 4 new customers. Each new customer cost her $60 ÷ 4 = $15.
If a customer buys one cake and disappears, Maria made $28 − $15 = $13. For 3 hours of work.
Repeat orders. But Maria's customers come back: on average 3 times a year (birthdays, holidays). Then:
- Margin per customer per year: $28 × 3 = $84
- Acquisition cost: $15
- Ratio: $84 ÷ $15 = 5.6
Every dollar she spends on ads comes back as roughly five and a half dollars of margin. The ads work, and she can spend more on them. Whether Maria is happy earning $9.33 an hour is a separate question. That's a question about price, and it's what the next lesson covers.
Example 2. Writing for local businesses with AI
James writes website copy and social media posts for small companies. AI helps him get the work done faster. A client pays him $300 a month.
What one client costs him per month:
| Cost | Amount |
|---|---|
| Paid image generator (credits used for this client) | $10 |
| Payment processing fee (say 3%, just for this example) | $9 |
| Total in cash | $19 |
Cash margin: $300 − $19 = $281. Looks great.
But James spends 8 hours a month on each client: gathering the details, the writing, revisions, calls. He's decided his time should be worth at least $25 an hour. So the time he puts into a client is worth 8 × $25 = $200, and his honest margin is $281 − $200 = $81 a month.
Acquisition cost. James doesn't run ads; clients come through people he knows. But he spends about 10 hours on each new one: messages, two free consultations, a written proposal. That's 10 × $25 = $250.
How long a client stays. Six months on average.
- Honest margin over the client's lifetime: $81 × 6 = $486
- Acquisition cost: $250
- Ratio: $486 ÷ $250 ≈ 1.9
The conclusion isn't obvious: the business is alive, but the margin is thin. If clients start leaving after 3 months, the ratio drops below 1 ($81 × 3 = $243, less than the $250 it took to land them), and every new client eats up time that never pays off. Word of mouth seemed free until James counted his hours.
What to do with these numbers
There are three levers, and you only see them once you've done the math:
- Raise your margin per customer: a higher price, lower costs per customer, fewer hours thanks to templates and AI.
- Lower your acquisition cost: a shorter path from the first message to payment, a ready-made proposal instead of a long back-and-forth.
- Keep customers longer: ongoing work instead of one-off jobs, a clear report on the results.
A common rule of thumb: a customer's lifetime value should be at least 3 times what it cost to acquire them. It's not a law, just a rough check. A ratio below 1 means you lose money on every new customer.
Common mistakes
❌ Counting only money and forgetting your time. In a service business, time is often the biggest cost. Leave it out and your margin looks several times better than it really is.
❌ Mixing up revenue and earnings. $50 for a cake doesn't mean $50 in your pocket.
❌ Assuming customers who come through friends are free. Messages, meetings and free consultations cost hours. Hours cost money.
❌ Doing the math on your best customer. One customer orders every week, the rest order once. Use the average, not the record.
❌ Forgetting fees. Your payment processor (Stripe, Square, PayPal), your bank, marketplace fees, currency conversion when a client pays from abroad. Each one is small; together they add up.
❌ Giving your first customer a discount forever. A discount on the first order eats your margin once. A "forever" discount eats it every month.
Practice
Exercise: the unit economics of your business (25 minutes)
Take your current work or your idea. If you don't have a business yet, pick a service you could sell.
Step 1. Fill in the table. Where you don't know a number exactly, put in an honest estimate and mark it with a "?".
| Question | Your number |
|---|---|
| How much one customer pays per order or per month | |
| What costs come up for each customer (in cash) | |
| How many hours one customer takes | |
| How much you want to earn per hour | |
| How much money and how many hours it takes to find one customer | |
| How many times a customer buys, or how many months they stay |
Step 2. Work out your margin per customer, your acquisition cost and the ratio between them. Check yourself with the Calculators.
Step 3. Ask an AI assistant to check your math and find the weak spot. A sample prompt:
Here are the numbers for my business: [paste the table]. Calculate my margin per customer including my time, my customer acquisition cost and my customer lifetime value. Explain in plain English which number is the weakest and which two actions would improve it. Don't make up numbers: if something is missing, ask me.
AI is good at doing math and explaining it, but it can slip on arithmetic or quietly fill in the numbers you didn't give it. Double-check the final numbers yourself or with the calculator.
Step 4. Write down one thing you'll do this week to improve your weakest number.
Key takeaways
Revenue tells you nothing about the health of a business. What tells you is the margin per customer and what it costs to bring that customer in.
Your time is a cost. Until you count it, you don't know how much you really earn.
A customer's lifetime value should be clearly bigger than what it cost to acquire them. If it's smaller, more customers means bigger losses.
Next lesson
→ How to price your services: the price floor, the market and the value to your client.
To go deeper (an optional library lesson): Unit economics of an AI stack (the unit economics of an AI business at three levels).
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