Customer acquisition cost is what you spend to win one customer. Lifetime value is what that customer is worth to you over the whole relationship. Compare them and you have the most important sanity check in any business that pays to grow.
Calculating CAC honestly
Divide everything you spent on acquiring customers in a period by the number of customers you acquired. The word doing the work in that sentence is “everything”.
- Ad spend, obviously.
- Salaries and contractor fees for anyone in sales or marketing, or the share of their time spent on it.
- Software: CRM, email tools, analytics, landing page builders.
- Agency retainers, freelancers, content and design costs.
- Commissions, referral fees and discounts given to close a sale.
If you spend $12,000 across all of that and gain 40 customers, your CAC is $300. Counting only the $6,000 of ad spend would have told you $150 and made a marginal channel look excellent. Blended CAC — everything divided by everyone — is the number that governs whether the business works. Channel-level CAC is what you use to decide where the next dollar goes.
Try it freeCustomer Acquisition Cost (CAC) CalculatorFind what one new customer really costs to win.Calculating LTV without flattering yourself
The simple form is average order value × purchase frequency per year × gross margin × expected years of retention. A customer spending $180 four times a year at a 45% gross margin, staying three years, is worth $972.
Two things go wrong here. First, people use revenue instead of gross margin, which inflates LTV by whatever their cost of goods happens to be — often doubling it. LTV must be a profit figure, or you are comparing a profit cost against a revenue benefit. Second, retention assumptions are usually optimistic. If you have been trading eighteen months, you do not know your five-year retention, and assuming it is the number that makes the maths work is a well-trodden path to failure.
Until you have real cohort data, cap your retention assumption at something you have actually observed. An LTV built on a three-year assumption from an eight-month-old business is a forecast wearing the costume of a metric.
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The ratio, and why 3:1
The conventional target is an LTV to CAC ratio of at least 3:1. At $972 of lifetime value against $300 of acquisition cost you are at 3.24:1, which is healthy.
The logic behind three is that gross-margin lifetime value still has to cover everything acquisition does not: product development, support, rent, administration, and eventually profit. A ratio near 1:1 means you are buying revenue at cost. Below 1:1 you are paying people to take your product.
A ratio far above 3:1 is not automatically good news either. A business running at 8:1 is usually underspending — there is profitable growth on the table that a competitor will take. Very high ratios often signal timidity rather than efficiency.
Try it freeCustomer Lifetime Value (LTV) CalculatorEstimate the total profit one customer brings.Payback period is the number that keeps you solvent
The ratio tells you whether a customer is eventually worth acquiring. It says nothing about when. If it takes eighteen months to recover $300 of CAC, then every customer you add makes your cash position worse for a year and a half, and growing faster makes the hole deeper. Businesses have gone under with excellent LTV:CAC ratios for exactly this reason.
Divide CAC by the gross profit a customer generates per month. Under twelve months is generally manageable; under six is comfortable. Beyond eighteen you need either external funding or a slower growth rate, and pretending otherwise is how a growing company runs out of money.
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Frequently asked questions
- What should be included in CAC?
- All sales and marketing costs for the period: ad spend, salaries and contractors, software, agency fees, commissions and acquisition discounts, divided by customers gained in that period.
- Should LTV use revenue or profit?
- Gross profit. Multiply by your gross margin. Using revenue overstates lifetime value by the whole cost of goods and makes unprofitable acquisition look viable.
- Is a high LTV:CAC ratio always good?
- No. Above roughly 5:1 usually means you are underinvesting in growth and leaving profitable customers to competitors.
- What is CAC payback period?
- CAC divided by the monthly gross profit per customer — how long until you recover the acquisition cost. Under twelve months is generally healthy; beyond eighteen creates real cash-flow strain.
General information only — not tax, legal, accounting or financial advice. Rates change and individual circumstances vary. Confirm figures with the CRA, the IRS, your state or provincial authority, or a licensed professional before acting on them.
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