Short answer: How do you calculate customer lifetime value? You multiply average order value by yearly purchase frequency and by average customer lifespan, and that is revenue-based LTV. Multiply the result by gross profit margin and you get profit-based LTV. Dividing profit-based LTV by customer acquisition cost gives the LTV/CAC ratio, and the common view is that 3:1 and above is healthy. The payback period is CAC divided by monthly customer profit. Rebel Co. Group built this tool so you can set the limit of your ad budget by customer lifetime, not by the first order.
Take average order value from your e-commerce panel or from the average purchase revenue in the GA4 Monetization report. For yearly purchase frequency, divide the total number of orders in the last 12 months by the number of unique customers who bought in the same period, and platforms such as Shopify give this in the customer report. Estimate customer lifespan from a cohort report or from the share of customers who placed their first order two years ago and still buy today, and if you have no data, 1.5-2 years is a realistic start. Enter gross profit margin from your accounting, and CAC as total spend on Google Ads and Meta Ads Manager divided by the number of new customers won in the period.
The calculator works with the values you enter. Your data stays in your browser and is never sent to a server. Results support decisions and do not replace accounting records.
Formula
Customer lifetime value is the product of a customer's average order value, purchase frequency and lifespan, and for a profitable decision this value is multiplied by gross margin.
- LTV (revenue) = Average order value x Orders per year x Customer lifespan (years)
- LTV (profit) = LTV (revenue) x Gross profit margin
- LTV/CAC = LTV (profit) / Customer acquisition cost
- Monthly customer profit = Average order value x Orders per year x Gross profit margin / 12
- Payback period (months) = CAC / Monthly customer profit
The difference between the two LTVs matters. Revenue-based LTV looks good in marketing decks but cannot be compared with CAC, because profit pays for CAC, not revenue. Use profit-based LTV for decisions. The payback period is a cash flow question: however high LTV is, the ad money leaves today and the profit comes back over months. The longer this period gets, the more your growth needs financing.
Worked example
Let us calculate a cosmetics brand with a 70 USD average order value, 3 orders a year, a customer who stays 2 years on average, a 40% gross profit margin and a 35 USD acquisition cost per customer.
| Step | Calculation | Result |
|---|---|---|
| LTV (revenue) | 70 x 3 x 2 | 420 USD |
| LTV (profit) | 420 x 40% | 168 USD |
| LTV/CAC | 168 / 35 | 4.8 |
| Monthly customer profit | 70 x 3 x 0.40 / 12 | 7 USD / mo |
| Payback period | 35 / 7 | 5 months |
The first order alone leaves 28 USD of profit, so CAC is not covered on the first order. What makes this brand profitable is the second and third orders.
Here is how to read it: someone who looks only at the first order says this brand loses 7 USD on every customer. Someone who looks at customer lifetime sees every 35 USD turn into 168 USD of profit over two years, and might even consider raising CAC to 50 USD. The same data leads to two different growth decisions. What makes the difference is the horizon of the calculation.
How to read the result
If the LTV/CAC ratio is above 3, your customer acquisition model is healthy, between 1 and 3 it is fragile, and below 1 you lose money on every new customer.
- Below 1: The profit a customer leaves over their lifetime does not cover the cost of winning them. Stop growing, and fix repeat purchases or margin first.
- Between 1 and 3: Profitable on paper, but fixed costs, returns and cash flow can easily wipe out this range. Focus on shortening the payback period.
- Between 3 and 5: The healthy growth band. You can raise the budget and let CAC rise a little.
- Above 5: Strong, but often a sign that you are not investing enough. Winning more customers at a higher CAC can grow total profit.
For the payback period, a common target in e-commerce is under 12 months, and 18 months is acceptable for subscription models. A payback under 6 months means you can run your ad budget on its own profit. If you are not sure about your lifespan estimate, also calculate the result with a 1-year lifespan, and the gap between the two results is the size of your risk.
A brand that looks for profit on the first order leaves the repeat customer to its competitor. The limit of an ad budget is drawn by the customer lifetime, not by the first cart.
Common mistakes
- Guessing customer lifespan. The assumption that "customers stay with us for 5 years" inflates LTV. Use cohort data: see what share of the customers who arrived 24 months ago is still active, and derive the lifespan from that.
- Comparing revenue-based LTV with CAC. A 420 USD LTV against a 35 USD CAC looks like 12 times, while the profit-based ratio is 4.8. The ratio you decide on is always the profit-based one.
- Counting one-time buyers and loyal customers in the same pool. A customer who buys once from a campaign and leaves pulls the average down, and a loyal customer pulls it up. Calculate LTV by segment and set ad targets by segment.
- Writing only ad spend into CAC. Agency fees, creative production, first-order discounts and free-shipping offers are acquisition costs too. An incomplete CAC makes the ratio look better than it is.
- Ignoring cash flow. LTV arrives over two years, while CAC is paid today. If the payback period goes beyond 12 months, growth needs outside financing. Reading the ratio alone is not enough.
How to improve this number
- Raise repeat purchase frequency. This is the strongest lever on LTV. For post-order email flows, replenishment reminders and complementary product suggestions, see the email automation guide.
- Extend customer lifespan. A loyalty program, early access for members and personal communication keep a customer from going to a competitor. For the setup, see the customer loyalty and CRM guide.
- Grow average order value. Bundles and a shipping threshold improve both LTV and payback on the first order. The methods are in the guide to raising order value.
- Lower CAC. Conversion rate, creative quality and channel mix set CAC. The concrete moves are in the guide to lowering CAC.
- Reactivate with WhatsApp. A personal message and a small incentive to a customer who has not ordered for 90 days costs far less than winning a new customer with ads. For the setup, see the WhatsApp marketing guide.
- Set target CAC by segment. Allow a higher CAC in a high-LTV segment and trim the budget in a low-LTV one. You can build segments by first product category, first order value or acquisition channel. The full theory is in the article on unit economics, CAC and LTV.
Frequently asked questions
What should the LTV/CAC ratio be?
The common rule is 3:1 or higher. That means the profit a customer leaves over their lifetime should be at least three times the cost of acquiring them. Below 1 is a loss, 1-3 is fragile and 3-5 is the healthy growth band. A ratio above 5 looks strong, but it often shows you are not investing enough, and raising CAC a little to win more customers can increase total profit. Always calculate the ratio with profit-based LTV, because a revenue-based ratio misleads.
How do I find customer lifespan?
The most reliable way is cohort analysis. In GA4 or your e-commerce panel, follow the customers who placed their first order in a given month and read the share still buying after 12, 18 and 24 months. Alternatively, calculate the annual churn rate, because lifespan is 1 divided by the churn rate. If you lose 50% of customers a year, lifespan is 2 years. If you have no data, start with 1.5-2 years and update it every quarter.
Why does the payback period matter?
The LTV/CAC ratio describes profitability, while the payback period describes cash flow. Even with a ratio of 4, if it takes 14 months to earn back CAC, cash leaves your account throughout the growth period and you need outside financing. Under 12 months is a common target in e-commerce, and under 6 months means you can run your ad budget on its own profit. The fastest way to shorten payback is to raise the cart value on the first order and the speed of moving to a second order.
What costs go into CAC?
All the spending you do to win a new customer. That includes ad spend, agency management fees, creative and video production, influencer payments, the first-order discount and the cost of a welcome free-shipping offer. Divide the total by the number of new customers won in the period, not by all orders. Remarketing spend aimed at existing customers is written to retention cost, not CAC, so keep the two apart.
How do I use LTV in ad targets?
Take one third of profit-based LTV as your target CAC and enter it as the target CPA in Google Ads and as the cost per result goal in Meta. If LTV is 168 USD, the target CAC is 56 USD, and even if first-order profit stays below it, the campaign is profitable over the customer lifetime. This approach gives you room in the auctions that competitors looking only at first-order ROAS drop out of. If you have segment-based LTV, set a separate target for each segment.