How to Calculate CAC and LTV for a Store or a Service Business

Customer acquisition cost is everything you spent to win new customers in a period, divided by the number of new customers who actually paid; lifetime value is the margin a customer leaves over the relationship. The decision that comes out of the two numbers is simple: does a customer's margin cover what it cost to acquire them, and in how many months?

This is for owners and finance or marketing managers in e-commerce, training and B2B services. It follows on from high ROAS, losing money: there, the ad is judged by collected revenue; here, the customer is judged by the margin they leave over months.

What do CAC and LTV mean in practice?

Customer acquisition cost (CAC) is the total cost of acquiring new customers in a period, divided by the number of new customers who paid in that period. I calculate it two ways: paid CAC for advertising channels only, and blended CAC, which divides all acquisition cost by all new customers, including those who arrived without an ad. Andreessen Horowitz's well-known piece on startup metrics warns that the blended figure alone does not tell you whether paid spend is profitable.

Customer lifetime value (LTV) is the contribution margin a customer leaves over the relationship. Contribution margin is what remains of an order's revenue after the variable costs of serving it: product cost, shipping, payment and collection fees, packaging, and the effect of returns.

Payback period is the number of months it takes a cohort's cumulative margin to cover what it cost to acquire them.

The CAC sheet: what goes into acquisition cost, and what gets forgotten

This sheet is the first calculation tool, and the part most reports cut short. Copy it and fill in one month's figures from your accounts.

Item	Include in CAC?	Note
Ad spend on every platform	Yes	Google, Meta, Snapchat, TikTok and X together, not one platform
Agency or freelancer fees	Yes	Even if they are a fixed monthly fee
Ad content production	Yes	Photography, design and editing made for ads
Share of marketing and sales salaries	Yes	In proportion to time spent winning new customers
Marketing, CRM and WhatsApp Business tools	Yes	The acquisition share, including paid template messages
First-order discounts, coupons, referral and influencer fees	Yes	Among the most forgotten items; a16z calls leaving them out a common mistake
Free introductory sessions and samples	Yes	Especially in training and services
Shipping and cash-on-delivery fees on the first order	No	They belong in order margin, so they aren't counted twice
Serving existing customers, loyalty programs	No	They affect customer value, not acquisition
The denominator		New customers who paid, after cancellations, refused deliveries and returns

That last line matters most in Saudi Arabia. In a store that relies on cash on delivery (the customer pays the courier at the door), an order refused at the door is not a customer, and dividing cost by orders instead of paying customers makes CAC look lower than it is.

Why calculate LTV on margin, not revenue?

Because revenue is not what you keep. A customer who spends SAR 1,200 a year at a 40% contribution margin leaves SAR 480, and comparing SAR 1,200 with acquisition cost makes every campaign look profitable. The a16z article itself lists calculating lifetime value on revenue among the common mistakes.

The method I use:

1. Pick a cohort: all customers who made their first purchase in one month.
2. Calculate contribution margin per order, after removing VAT from revenue.
3. Track the same cohort after 3, 6 and 12 months: how many orders per customer, on average, so far?
4. 12-month LTV = average cumulative orders per customer × contribution margin per order.

I stop at 12 months on purpose. Projecting years of repeat buying for a store that is one year old produces a comfortable number, not an honest one. For companies with little data, a16z suggests measuring historical value over a fixed period, such as 12 or 24 months, rather than projecting a long retention curve.

Worked example: an online store in Riyadh (hypothetical)

This is a hypothetical example with round numbers for a store selling home goods, with part of its orders paid cash on delivery.

Acquisition cost for one month (hypothetical):

Item	Amount
Ad spend	SAR 38,000
Agency fees	SAR 6,000
Tools	SAR 1,600
Share of marketing salaries	SAR 8,000
First-order discounts	SAR 4,000
Total	SAR 57,600
First orders	560
New customers who paid, after refusals and returns	480
CAC	SAR 120

In this example the ad dashboard would show a cost per purchase of about SAR 68, because it divides ad spend alone by all orders. The gap between 68 and 120 is what reports that only count advertising hide.

Lifetime value of the same month's cohort (hypothetical): average order value SAR 220 excluding VAT, contribution margin 40%, so SAR 88 per order.

After	Average cumulative orders per customer	Cumulative margin per customer
1 month	1.0	SAR 88
3 months	1.2	SAR 105.60
6 months	1.4	SAR 123.20
12 months	1.7	SAR 149.60

How to read it: cumulative margin passes the SAR 120 CAC between month 3 and month 6, so that is the payback period. Twelve-month LTV on margin is about SAR 150, a ratio of roughly 1.25:1. Calculated on revenue (1.7 × SAR 220 = SAR 374), the ratio would be about 3.1:1, and the store would appear to meet the popular rule while in fact barely covering its acquisition cost in the first year.

Worked example: a training center in Amman (hypothetical)

This is a hypothetical example with round numbers for a center selling professional courses, where the first course opens the relationship rather than ending it.

Item (hypothetical)	Amount
Ads	JOD 2,800
Share of sales salaries	JOD 1,800
Tools	JOD 200
Free introductory sessions	JOD 600
Total acquisition cost	JOD 5,400
New students enrolled and paid	36
CAC	JOD 150
First course price, excluding tax	JOD 300
Delivery cost per seat (trainer, room, materials)	JOD 120
First-course margin	JOD 180
Share taking a second course within 12 months	40%
Second-course margin	JOD 160
12-month LTV	180 + (40% × 160) = JOD 244

Payback here is fast. If the course is paid upfront, its margin covers acquisition cost on enrollment day; if it is paid in three monthly installments, cumulative margin reaches JOD 180 in month three. The lifetime value, though, comes from the second course, which means from what happens with graduates after the first course ends, not from the ad.

Ratio or payback: which matters more for a small business?

Payback first, then the ratio. The ratio tells you whether a customer is profitable eventually; payback tells you when the money comes back, and small businesses run out of cash before they run out of profit.

The 3:1 rule needs its context. David Skok framed it as a guideline for software-as-a-service companies and assumed a gross margin of 80% or more. Alongside it he suggested recovering acquisition cost in under 12 months, noting that this guideline dates from 2011 and that companies selling to enterprises work well with payback closer to 20 months. A store on a 40% margin, or a training center with real delivery costs, is not a software company, so I always apply the ratio to margin.

Situation	What I read first	Why
A cash-constrained store with cash on delivery	Payback in months	Collection is delayed and stock needs financing
A training center paid upfront	12-month LTV	Payback is fast; growth comes from the second course
B2B services with long contracts	Ratio and payback together	The first deal may not cover the cost of selling

How do you raise customer lifetime value?

By raising what each order leaves and how often customers come back, not only by cutting ad cost:

• Raise average order value through categories, bundles and offer structure; the method is in how to raise average order value.
• Design the second purchase: which product or course logically comes next, when it is offered, and by whom.
• Reduce orders refused at delivery by confirming orders before shipping, because each refused order raises CAC and lowers margin at once.
• Follow up after the sale with a system rather than by chance, as in lead follow-up on WhatsApp and CRM.
• Tell the ad platform what a new customer is worth. The customer acquisition goal in Google Ads lets you bid more for new customers in Search, Performance Max, Shopping and Demand Gen campaigns, and identifies existing customers from your own data, such as customer lists. The value you set should come from your margin calculation, not from a guess.

From my work

I judge marketing at revenue, and that includes what happens after the first sale. At CoderZ I work on an alumni program called «طمّني عليك» ("let me know how you're doing"): we reconnect with the academy's graduates, collect their feedback and answer their questions. I publish no figures about it. At Argan Package in Saudi Arabia, I set up the wholesale sales department, which brought in 15 new wholesale customers, with exclusive distribution in the Eastern Province and Jeddah. A wholesale customer's value, like a graduate's, doesn't show in the first order; it shows in the relationship afterward, which is why it is measured over months.

Where to start

Take the customers from one month, six months ago. Fill in the CAC sheet for that month with every item, and divide by those who actually paid. Then calculate contribution margin per order, track that cohort to today, and write one line: in which month did margin cover acquisition cost? That line is more useful than any ratio in a slide deck.

If you want to review these numbers together, from the ad through to collected revenue, that is the work in a revenue-based marketing audit. Request a consultation, and we start from your accounts and your store or CRM reports.

Want your team trained on this? Corporate training programs.