--- title: "CAC and LTV, explained: what a customer costs and what they’re worth" description: "CAC and LTV in plain English with a worked example: what one customer costs you, what they’re worth, the 3-to-1 rule of thumb, and payback time." url: https://dumbcmo.com/blog/cac-and-ltv-explained category: "Knowing what works" tags: ["cac", "ltv", "metrics", "unit economics"] published: 2026-10-25 updated: 2026-10-25 reading_time: 4 min author: "The DumbCMO" --- # CAC and LTV, explained: what a customer costs and what they’re worth > **TL;DR:** CAC is what you spend on marketing to win one new customer. LTV is what that customer pays you over time. If a customer is worth much more than they cost, grow. If not, fix prices, repeat visits or costs before you spend more. [Notebook](https://dumbcmo.com) › [Blog](https://dumbcmo.com/blog) › Knowing what works › CAC and LTV, explained: what a customer costs and what they’re worth Two gyms open in the same building. Both spend $1,500 a month on ads and flyers. Both get 30 new members a month. Gym A charges $40 a month, and members quit after two months. Gym B charges $30, but members stay for a year and a half. Gym A looks like it’s doing better on day one. Gym B is the one still open in three years. The difference is two numbers: what a customer costs and what a customer is worth. ## In normal-people words **CAC is what one new customer costs you. LTV is what they pay you, in total, for as long as they stay.** - **CAC** (customer acquisition cost (Customer acquisition cost: marketing spend divided by new customers.)) = marketing spend ÷ new customers. - **LTV** (lifetime value (Lifetime value: what one customer pays you over the whole time they stay.)) = what they spend each time × how often × for how long. If LTV is comfortably bigger than CAC, every new customer makes you money. If not, more marketing just loses money faster. ## The two gyms, worked out **Same marketing spend, very different businesses** | Number | Gym A | Gym B | | --- | --- | --- | | Marketing per month | $1,500 | $1,500 | | New members per month | 30 | 30 | | CAC (cost per new member) | $50 | $50 | | Fee per month | $40 | $30 | | Months a member stays | 2 | 18 | | LTV (revenue) | $80 | $540 | | LTV kept, at 50% margin | $40 | $270 | | Kept ÷ cost | 0.8 to 1 | 5.4 to 1 | **What a member costs vs what you keep** | | Cost to win them | What you keep from them | | --- | --- | --- | | Gym A | $50 | $40 | | Gym B | $50 | $270 | *The two-gym example above, using profit (50% margin), not revenue.* Gym A loses $10 on every member it signs up. **More ads would make it go broke faster.** Gym B can afford to spend much more to find members. > **The DumbCMO:** Gym A’s fix isn’t more Instagram ads. It’s working out why everyone leaves in month two. ## The chai stall version A new office opens near the chai stall. The chai-wallah gives the whole office a free first cup to win them over. That’s his CAC. If they come back every day for two years, those free cups were the best money he ever spent. If they try it once and go to the café next door, **he just gave away chai.** ## The rule of thumb: 3 to 1 A common rule of thumb is that what you keep from a customer (LTV, measured as profit) should be at least three times what they cost to win ([Chargebee](https://chargebee.com/resources/glossaries/ltv-cac-ratio)). It’s a heuristic, not a law. **Reading your ratio** - **If** Below 1 to 1 **→ then** You lose money on every new customer. Stop scaling marketing. - **If** Between 1 and 3 to 1 **→ then** Thin. Raise prices, get people back more often, or spend less per customer. - **If** 3 to 1 or better **→ then** Healthy. You can afford to spend more to grow. - **If** Way above 5 to 1 **→ then** You might be spending too little. You could probably grow faster. ## The other number: payback time Even with a great ratio, cash matters. **Payback time** is how many months until a customer has paid back what they cost. Gym B gets $15 profit a month per member, so a $50 member pays back in under four months. If payback takes two years, you can run out of cash while “doing well” ([Chargebee](https://chargebee.com/resources/glossaries/ltv-cac-ratio)). Do your own maths in 30 seconds with the [customer cost calculator](/tools/customer-cost-calculator). ## Do this today - [ ] Add up last month’s marketing spend: ads, agency, tools, printing. All of it. - [ ] Count last month’s brand-new customers. Divide. That’s your CAC. - [ ] Estimate how much a typical customer spends with you in total. Be pessimistic. - [ ] Put both into the [calculator](/tools/customer-cost-calculator) and read the verdict. ## Not-so-frequently asked questions ### Should LTV use revenue or profit? Profit. Revenue makes the ratio look better than it is, because you don’t keep all the money a customer pays. ### I’m new. How do I know how long customers stay? You don’t yet. Guess low, and update the number every few months as you learn. ### Does word of mouth count in CAC? Customers who came free lower your average CAC. That’s fine, but track paid customers separately so you know what ads really cost. ### What’s the fastest way to improve the ratio? Usually keeping customers longer. Getting one more visit from people who already like you is cheaper than finding new people. ## Things your agency won’t say - An agency reporting “cost per lead” without ever asking your LTV is flying blind with your money. - Most businesses have a retention problem dressed up as a marketing problem. - Raising prices is a marketing decision. It changes LTV overnight. ## Jargon Jail **Locked up: “Unit economics”** Sounds like an MBA lecture. **It means: do you make money on one customer, yes or no?** CAC and LTV are the two numbers that answer it. ## Where to go next - Try it: [What does a customer cost me?](/tools/customer-cost-calculator) - Where CAC comes from: [What are paid ads?](/blog/what-are-paid-ads) - Keep customers longer: [WhatsApp Business basics](/blog/whatsapp-business-basics) - Words you’ll hear: [CAC](/glossary#cac), [LTV](/glossary#ltv), [churn](/glossary#churn), [KPI](/glossary#kpi) ## Sources 1. Chargebee, [“LTV:CAC ratio”](https://chargebee.com/resources/glossaries/ltv-cac-ratio): the 3:1 rule of thumb and payback time. 2. Improvado, [“LTV to CAC ratio: how to calculate, interpret and improve it”](https://improvado.io/blog/ltv-to-cac): why LTV should use profit, not revenue. 3. The two gyms are a worked example, not real businesses. --- From [DumbCMO](https://dumbcmo.com): The marketing notes you were too embarrassed to take.