Customer acquisition cost for memberships

If you spent $2,000 on marketing and gained 40 new members, each member cost you $50 to acquire. That figure, known as customer acquisition cost or CAC, is one of the most practical numbers a membership owner can know. It tells you whether your marketing pays for itself, which channels are worth expanding, and how long you wait before a new member has earned back what it cost to win them.

The arithmetic is simple. The difficulty lies in deciding what counts as a cost, and in resisting the temptation to leave out anything that makes the number look worse.

What goes into acquisition cost

CAC is total acquisition spending in a period divided by the new paying members gained in that period. The spending should include everything you pay to attract and convert new members:

• Advertising spend on any platform.
• Affiliate and referral commissions, and the cost of any referral rewards.
• Discounts and free months given to new members, valued at what they would otherwise have paid.
• Marketing tools and software used mainly for finding new members.
• Freelancers or staff who work on marketing, such as a copywriter or an ads manager.
• Event costs, sponsorships and printed materials used to promote the membership.

Leave out the costs of serving existing members, such as hosting, member support and content for the members' area. Those belong to delivering the membership, not selling it. Content that does both, such as public articles that bring in search visitors, is a judgment call; pick a share and apply it consistently.

What about your own time?

For solo owners, the biggest acquisition cost is often time: writing, posting, recording, emailing. It is worth calculating CAC two ways, once with cash only and once with your hours valued at a realistic rate. The first tells you about cash flow. The second tells you whether a channel is a good use of your working week. Ten hours a week on social media for four new members a month is expensive, even if it costs nothing in cash.

Blended and channel CAC

Blended CAC puts all acquisition costs and all new members together. It is useful for a big-picture view, but it can hide an expensive channel behind a cheap one.

Take a hypothetical dog training membership over one quarter. The figures are made up to show the method:

• Paid ads: $3,000 spent, 40 new members, CAC $75.
• Affiliate commissions: $600 paid, 20 new members, CAC $30.
• Email and free content: $400 on tools and a freelance editor, 40 new members, CAC $10.

Blended CAC is $4,000 ÷ 100 = $40. That looks healthy, but it averages a $10 channel with a $75 one. Channel CAC depends on knowing where each member came from; see tracking where new members come from.

Payback period: how long until a member pays off

Payback period is how many months of fees it takes to recover the cost of acquiring a member. Divide CAC by the monthly margin per member: the monthly price minus what it costs you to serve them.

If the dog training membership charges $25 a month and serving each member costs about $5, the monthly margin is $20. Members from paid ads pay back in $75 ÷ $20, just under four months. Affiliate members pay back in a month and a half, and email members in about two weeks.

Payback matters because it ties up cash. If most members stay a year or more, a four-month payback is comfortable. If many members leave after three months, a four-month payback means you lose money on each of them.

Comparing CAC with lifetime value

The fuller test is to compare CAC with the margin a member produces over their whole membership. If you have worked out member lifetime value, divide it by CAC.

Suppose the average dog training member stays 15 months. Lifetime margin is $20 × 15 = $300. For ads members, that is four times their CAC; for affiliate members, ten times. Both are profitable, but the ads leave far less room for error, especially if ad prices rise or if ads bring members who stay a shorter time than average. Where you can, calculate lifetime value by channel, not just overall.

There is no universal right ratio. A higher ratio gives you more safety. A very high ratio can mean you are under-investing and could afford to spend more on your best channels. Before scaling any paid channel, make sure you know your numbers before buying traffic.

Lowering CAC without starving growth

• Improve conversion before buying more traffic. If a larger share of visitors join, every channel gets cheaper at once.
• Lean on channels that compound. Referrals, search traffic and partnerships often get cheaper per member over time, while ads cost the same every month.
• Fix or cut the most expensive channel. Try new audiences or messages, and if CAC stays high after a fair test, move the budget elsewhere.
• Keep members longer. Retention does not lower CAC, but it raises lifetime value, which means you can afford a higher CAC.

Calculating yours

1. Pick a period of at least three months, to smooth out lumpy spending and sign-ups.
2. List every acquisition cost from that period, including discounts, rewards and commissions.
3. Count new paying members in the same period, excluding trials that never paid.
4. Calculate blended CAC, then CAC for each channel you can measure.
5. Calculate the payback period for each channel using your monthly margin per member.
6. Compare with lifetime value, then decide which channel to expand and which to rethink.