---
title: "Unit economics: AOV, CAC, LTV and contribution margin"
description: "Why unit economics decide survival Unit economics describe the profit or loss on each order and each customer. A store can grow revenue rapidly and still…"
url: https://optimizeall.com/learn/ecommerce-marketing-and-growth/unit-economics
updated: 2026-10-05
---

E-commerce Marketing and Growth · Unit economics and e-commerce analytics · lesson 18 of 20 · 12 min

# Unit economics: AOV, CAC, LTV and contribution margin

## Why unit economics decide survival

**Unit economics** describe the profit or loss on each order and each customer. A store can grow revenue rapidly and still run out of cash if each new customer costs more to acquire than they ever generate. Understanding unit economics lets you decide how much you can afford to spend on growth.

## Key definitions

| Metric | Formula | Notes |
|---|---|---|
| AOV (average order value) | Revenue / Number of orders | Use net revenue after discounts |
| Gross margin | (Revenue - Cost of goods) / Revenue | Product-level profitability |
| Contribution margin (per order) | Revenue - COGS - Shipping & fulfilment - Payment fees - Returns allowance - (variable marketing, if included) | The profit each order contributes to fixed costs |
| CAC (customer acquisition cost) | Acquisition marketing spend / New customers acquired | Use new customers, not all orders |
| LTV (customer lifetime value) | Contribution per order x Orders per customer over a period | Use contribution, not revenue |
| LTV:CAC ratio | LTV / CAC | Commonly discussed guide: comfortably above 1; many aim for around 3 over a sensible time frame |
| Payback period | Time for cumulative contribution from a customer to exceed CAC | Shorter payback reduces cash strain |

## Worked contribution margin example

Illustrative numbers for one order:

```
Selling price (net of discount):        100
Cost of goods:                          -40
Shipping & fulfilment:                  -12
Payment processing fees:                 -3
Returns allowance (avg cost of returns): -5
Contribution margin before marketing:     40  (40%)
```

If the average CAC is 30, the **first order** contributes 40 - 30 = 10 after acquisition cost. The customer pays back on the first order.

## LTV example

```
Contribution per order: 40
Average orders per customer over 24 months: 2.5
LTV (24 months, contribution basis): 40 x 2.5 = 100
CAC: 30
LTV:CAC = 100 / 30 = about 3.3
```

Choose a realistic time frame for LTV (for example 12 or 24 months) and base it on **observed cohort data** rather than hopeful assumptions. Early-stage stores should be conservative.

## Why revenue-based LTV misleads

Calculating LTV from revenue (for example, 250 in revenue per customer) and comparing it to CAC (30) makes the business look far healthier than it is. Always use **contribution** — the money actually left after variable costs.

## Levers to improve unit economics

```
Raise contribution per order:  price, AOV, sourcing, shipping costs, payment mix, fewer returns
Lower CAC:                     creative, conversion rate, channel mix, organic and referral growth
Raise orders per customer:     retention flows, loyalty, subscriptions, product range
Shorten payback:               higher first-order margin, faster second purchase
```

## Cash flow and payback

Even with a healthy LTV:CAC ratio, a long payback period can create cash problems — you spend on acquisition today and recover over many months. Inventory purchases add further strain. Plan growth spend with cash flow in mind.

## Market considerations

- Cash on delivery refusals and returns can significantly change contribution — include them.
- Currency fluctuations affect cost of goods for importers.
- Marketplace fees reduce contribution for marketplace orders; calculate per channel.
- VAT or sales tax treatment varies — use net revenue.

## Hands-on: a unit economics calculator with payback

Put your definitions in code so everyone uses the same maths (all inputs illustrative; use net revenue excluding VAT):

```python
def unit_economics(aov: float, gross_margin: float, fulfilment: float, payment_fee_rate: float,
                   return_rate: float, return_cost: float, cac: float,
                   orders_per_year: float, years: int = 2) -> dict:
    """Contribution per order, LTV (contribution-based) and payback for one customer."""
    per_order = (aov * gross_margin                 # product margin
                 - fulfilment                        # pick, pack, ship
                 - aov * payment_fee_rate            # payment processing
                 - return_rate * return_cost)        # expected return handling
    if per_order <= 0:
        return {"contribution_per_order": round(per_order, 2), "warning": "each order loses money"}
    ltv = per_order * orders_per_year * years       # simple, undiscounted
    orders_to_payback = cac / per_order
    return {
        "contribution_per_order": round(per_order, 2),
        "ltv_contribution": round(ltv, 2),
        "ltv_to_cac": round(ltv / cac, 2),
        "orders_to_payback": round(orders_to_payback, 2),
    }

print(unit_economics(aov=62, gross_margin=0.58, fulfilment=7.5, payment_fee_rate=0.029,
                     return_rate=0.08, return_cost=9, cac=28, orders_per_year=2.2))
```

Use **cohort data** (actual repeat orders of customers acquired in a given month) rather than guesses for `orders_per_year`, and run the calculation separately by acquisition channel — LTV often differs sharply between, say, marketplace-acquired and creator-acquired customers.

## Market specifics worth modelling

- **Cash on delivery (Pakistan, parts of the Gulf)**: include refusal rates and the cost of failed deliveries; COD also delays cash receipt.
- **BNPL fees**: providers charge merchants fees that are typically higher than card fees; include them where BNPL is a large share of orders.
- **Marketplace fees**: commissions, fulfilment and advertising fees make marketplace contribution very different from own-store contribution.
- **Currency and duties**: for cross-border sales, include FX costs and who pays duties.

## Common mistakes

- Using revenue instead of contribution for LTV.
- Ignoring returns, fees and shipping.
- Calculating CAC with all orders instead of new customers.
- Assuming lifetime values from optimistic projections.
- Ignoring payback and cash flow.

## Using unit economics in decisions

Unit economics should shape everyday choices: whether to accept a marketplace's fees, how much commission to offer affiliates, what CAC target to set for each channel, whether a discount is worth running, and which products to promote. A simple rule many teams use is to set a maximum CAC per channel based on contribution-based LTV and an acceptable payback period, then review it monthly as data improves.

## Unit economics checklist

- [ ] Contribution margin per order calculated with all variable costs
- [ ] CAC calculated on new customers by channel
- [ ] LTV based on observed cohorts over a defined period
- [ ] LTV:CAC and payback reviewed monthly
- [ ] Channel-level unit economics (own store vs marketplaces)

## Video lecture: Unit economics: AOV, CAC, LTV and contribution margin

Lecture coming soon · 14 chapters · about 8 minutes. Read the full transcript below.

1. Unit economics
2. Why they decide survival
3. Key definitions
4. Revenue-based LTV misleads
5. Contribution, step by step
6. Levers
7. Market specifics
8. Simple example: Pakistani skincare (illustrative)
9. Realistic example: UK tea brand (illustrative)
10. Watch me do it: unit economics function
11. Cash flow and payback
12. Decisions with unit economics
13. Common mistakes
14. Recap

## Lecture transcript

### Unit economics

Here's the most important question in ecommerce, and it isn't how do we grow revenue? It's: does each order, and each customer, make money? Unit economics answers it. In this lecture you'll learn the key definitions, like contribution margin, customer acquisition cost, lifetime value and payback, why revenue-based lifetime value misleads, the levers that improve the numbers, market specifics like cash on delivery and marketplace fees, and how to use unit economics to make decisions. Then you'll watch me build a unit economics calculator in Python.

### Why they decide survival

Why do unit economics decide survival? Because growth multiplies whatever each order earns. If every order makes a little money, growth builds a profitable business. If every order loses a little, growth accelerates the losses, and cash runs out faster the more you sell. Many stores discover this too late, because revenue looks healthy while cash drains away. Knowing your unit economics lets you grow with your eyes open.

### Key definitions

Key definitions. Average order value, net of discounts and excluding tax. Gross margin: revenue minus the cost of the product. Contribution margin: gross margin minus variable costs per order, like fulfilment, shipping, payment fees and expected returns. Customer acquisition cost, or CAC: marketing spend divided by new customers acquired. Lifetime value, or LTV: the contribution a customer generates over their relationship with you. And payback: how many orders, or months, it takes to earn back the acquisition cost.

### Revenue-based LTV misleads

Here's why revenue-based lifetime value misleads. A customer who spends five hundred over two years sounds valuable. But if your contribution margin is twenty percent, they generate a hundred in contribution. If you paid eighty to acquire them, you've earned twenty in two years. That's thin. Revenue-based LTV encourages overspending on acquisition. Always calculate LTV from contribution, not revenue, and compare it with CAC. A common rule of thumb is to look for LTV comfortably above CAC, but your own cash position and payback period matter more than any ratio.

### Contribution, step by step

Let's make contribution margin concrete, because it's the number everything else depends on. Start with net revenue for an order: the price paid after discounts, excluding VAT. Subtract the cost of the products. That's gross margin. Now subtract every cost that happens because this order exists: picking and packing, the courier, packaging, payment processing, and an allowance for returns based on your actual return rate. What's left is contribution. Marketing comes next, because acquisition cost is spent per customer, not per order. Fixed costs, like salaries, rent and software, come last. If contribution per order is small or negative, no amount of marketing will fix the business.

### Levers

The levers that improve unit economics. Raise order value with bundles and thresholds. Improve gross margin through pricing, sourcing and product mix. Reduce fulfilment and packaging costs. Lower return rates with better product information. Negotiate payment fees, and steer towards cheaper methods where fair. Lower CAC by improving conversion and creative. And raise repeat purchase rates, which spreads acquisition cost over more orders. Small improvements across several levers compound.

### Market specifics

Market specifics change the numbers. With cash on delivery, common in Pakistan and parts of the Gulf, include refusal rates, the cost of failed deliveries and the delay before cash arrives. Buy-now-pay-later providers usually charge merchants higher fees than cards. Marketplace orders carry commissions, fulfilment and advertising fees, so their contribution can be very different from your own store's. And cross-border sales add currency conversion costs and duties. Model each one where it's a meaningful share of orders.

### Simple example: Pakistani skincare (illustrative)

A simple example with illustrative numbers. A Pakistani skincare brand sells an order of three thousand rupees. Product cost is twelve hundred, delivery and packaging three hundred, and payment and COD handling a hundred and fifty. But twelve percent of COD orders are refused, costing about three hundred in wasted delivery each. That's about thirty-six rupees per order on average. Contribution per order is roughly thirteen hundred. If acquisition costs nine hundred, the first order is profitable, but only if refusals stay low. Reducing refusals with WhatsApp confirmations directly improves unit economics.

### Realistic example: UK tea brand (illustrative)

Now a realistic scenario with illustrative numbers. A UK tea brand has an average order of sixty-two pounds and a fifty-eight percent gross margin. Fulfilment is seven pounds fifty per order, payment fees about three percent, and eight percent of orders are returned at a handling cost of nine pounds. That leaves about twenty-six pounds of contribution per order. Customer acquisition cost is twenty-eight pounds, and customers average two point two orders a year. So payback takes just over one order, and two-year contribution-based LTV is about a hundred and fourteen, around four times CAC. Healthy, if the repeat rate is real. The next step is checking it with cohort data.

### Watch me do it: unit economics function

Watch me build the calculator. I write a Python function with order value, gross margin, fulfilment cost, payment fee rate, return rate and return cost, CAC, orders per year, and years. It calculates contribution per order by subtracting fulfilment, payment fees and expected return costs from the product margin. If that's zero or negative, it warns that every order loses money. Otherwise it calculates contribution-based LTV, the LTV-to-CAC ratio, and how many orders it takes to pay back acquisition. I run the tea brand's numbers: about twenty-six pounds per order, LTV about a hundred and fourteen, a ratio around four, and payback in about one point one orders.

### Cash flow and payback

Cash flow and payback deserve their own focus. Even with good LTV, a long payback period means you're funding customers for months before they pay you back, which strains cash, especially when you're growing fast or holding stock for peak seasons. Cash on delivery adds another delay. So track payback in months, not just orders. Plan inventory purchases and ad budgets together. And be careful with growth that depends on customers paying back over a year or more, unless you have the cash to fund it.

### Decisions with unit economics

Use unit economics in decisions. Before scaling a channel, check contribution after that channel's costs and its customers' repeat rates. Before running a discount, recalculate contribution per order. Before adding a marketplace, include its fees. Before offering free delivery, model the threshold. And calculate by channel and by cohort, because customers from different channels often behave very differently. The numbers turn opinions into clear trade-offs.

### Common mistakes

Common mistakes. Using revenue instead of contribution. Ignoring returns, payment fees and COD refusals. Blending all channels into one average. Guessing repeat rates instead of using cohorts. Counting VAT as revenue. And celebrating growth while cash is shrinking. Each one makes the business look healthier on paper than it is in the bank.

### Recap

Recap. Unit economics decide whether growth builds a business or burns cash. Calculate contribution per order after all variable costs, measure CAC by channel, calculate lifetime value from contribution using real cohort data, and watch payback in months. Include market specifics like COD refusals, BNPL and marketplace fees. Try this now: run the calculator from the lesson text with your own numbers, once for your own store and once for your biggest marketplace, and compare contribution per order.

## Key takeaways

- Unit economics show profit or loss per order and per customer.
- Contribution margin subtracts all variable costs, including shipping, fees and returns.
- Calculate LTV on contribution over a defined period using observed cohorts.
- Watch LTV:CAC and payback period together to manage growth and cash.

## Try it

Build a unit economics sheet for a store with contribution per order, CAC by channel, 12-month LTV from cohort data (or assumptions labelled as such) and payback period.

- [Previous: Measuring and managing partner programmes](https://optimizeall.com/learn/ecommerce-marketing-and-growth/measuring-partner-programmes)
- [Next: E-commerce analytics: cohorts, customers and dashboards](https://optimizeall.com/learn/ecommerce-marketing-and-growth/ecommerce-analytics)
- [All lessons of E-commerce Marketing and Growth](https://optimizeall.com/learn/ecommerce-marketing-and-growth)