Blended CAC is total acquisition spend in a period divided by all new users in that period, paid and organic together. It is the honest number because it counts everything you spent and everyone you got. Lower it by growing the organic share, better creative, retention loops that feed referrals, and cutting channels that do not repeat.
The formula
Blended CAC = total acquisition spend in a period / new users acquired in that period.
Total acquisition spend includes everything you paid to get users: ad spend, creator fees, agency or contractor fees, tools used for acquisition, referral rewards, and a fair share of the time your team spent on growth. New users means every user who arrived in the period, no matter how. Paid, organic search, word of mouth, referral, press, all of it.
Two decisions to make once and keep: the period (I use a calendar month) and the definition of a user. For a free app, a user is usually an install or a signup. For a subscription app, you should also compute the same number with paying customers in the denominator. Label which one you mean every time.
Blended CAC vs paid CAC
Paid CAC = paid media spend / users attributed to paid media.
Paid CAC tells you what a channel costs at the margin. Blended CAC tells you what growth costs in total. You need both, for different questions.
- Use paid CAC to decide whether to raise or cut a specific campaign.
- Use blended CAC to decide whether the business is growing at a price it can afford.
- Watch the gap between them. A widening gap means organic is doing more of the work. A narrowing gap means you are buying more of your growth.
Why blended is the honest number
Paid CAC is easy to make look good. Move budget to retargeting, count only last-click installs, or exclude creator fees, and the number drops without anything real changing. Blended CAC does not care about attribution. It counts every dollar and every user. If the ratio is bad, the growth is expensive, however you label it.
It also captures the organic lift that paid creates. When a TikTok ad gets people to search for your app, those installs show up as organic. Paid CAC misses them. Blended CAC catches them. That is why I run every account on blended, including the one in the ZuAI case study.
A worked example
This is an example with round numbers, not a real account.
One month:
- Ad spend: $12,000
- Creator fees, tools, and allocated team time: $3,000
- Total acquisition spend: $15,000
- Users attributed to paid: 5,000
- Organic users (search, referral, word of mouth): 10,000
- Total new users: 15,000
Paid CAC = $12,000 / 5,000 = $2.40. Blended CAC = $15,000 / 15,000 = $1.00.
Same month, same spend, two very different numbers. If this app earns $0.25 in gross profit per user per month, the paid number looks scary and the blended number looks fine. If organic drops to 2,000 the next month, blended CAC jumps to $2.14 with no change in ad performance. That jump is the signal. Something in the product or word of mouth changed, and paid dashboards would never show it.
What moves blended CAC
Four levers, in the order I pull them.
- Organic share. The biggest lever by far. Every organic user lowers the average. Organic comes from product quality, search presence, content, and community. It is slow to build and slow to lose.
- Creative. On the paid side, creative decides CPM and hook rate, which decide cost per install. On ZuAI I test 150 or more creatives a month for this reason. A better hook is a cheaper user.
- Retention loops. Users who stay tell others. Users who churn in a week do not. Retention is not a CAC input on paper, but in practice it drives the organic share in the next period.
- Referrals. A share or invite feature inside the product turns each user into a small acquisition channel. Referral rewards count as spend, so measure the net effect.
A fifth lever is subtraction. Cut the channels that produce users once but never repeat. My rule: a channel that produces ten customers is an experiment. One that produces them repeatedly inside a predictable CAC range is a growth engine. Only growth engines belong in the budget.
The $0.02 ZuAI number in context
ZuAI went from roughly 10,000 users to 2 million users at a $0.02 blended CAC. People see that number and ask how to copy it. Context first.
- Consumer app. A broad audience with a problem many people have.
- Free install. The cost to try it was zero, so the path from view to install was short.
- Massive organic share. A large share of users arrived without a paid click, through sharing, search, and word of mouth. That is what pulls a blended number down to cents.
- Creative volume. About $300,000 a month in ad spend and 150 or more creatives a month. That volume is what finds the cheap hooks.
Take away the free install or the organic share and the number would be many times higher. If you sell a $30 a month subscription to a niche, your blended CAC should be nowhere near $0.02, and that is fine. The right question is not how low, but how it compares to what a user is worth. I go deeper in the ZuAI case study and in my AI app growth work.
When a low CAC is a trap
A low CAC with a low LTV is a leak, not a win. Traps I have seen in my campaigns:
- Cheap installs that never open the app twice. The CAC is low. The cost per retained user is not.
- Users from a market you cannot monetize. Installs are cheap there for a reason.
- Incentivized installs. People took the reward, not the product.
- A viral spike that inflates one month’s organic share and disappears the next.
The fix is to compute CAC against a retained or paying user, not just an install, and to compare it to lifetime value: the gross profit a user generates before they leave. If LTV is not comfortably above blended CAC, a low CAC is just a slow way to lose money.
Payback period
Payback period = blended CAC / monthly gross profit per user.
Using the example above: $1.00 CAC and $0.25 monthly gross profit per user gives a 4 month payback. If that is shorter than the average time a user stays, the growth pays for itself. If it is longer, you are financing churn.
Payback is the number I care about most when scaling, because it decides how fast spend can be recycled. A short payback lets you reinvest revenue into the next month’s acquisition. A long payback means every month of growth needs new cash. I built free calculators for CAC, LTV, and payback on my tools page so you can run your own numbers in a few minutes.
If you want help finding which lever moves your blended CAC, the app growth marketing service is where I do that work with founders, and the Goal Digger Club is where I share what I learn.
FAQ
What is a good blended CAC for an app?
There is no single good number. It depends on what a user is worth to you. A free consumer app with ads or a cheap subscription needs a CAC in cents or low single dollars. A business tool with a high annual contract can afford far more. The useful test is payback: recover the CAC in fewer months than a typical user stays, with room to spare.
Should I include founder time in blended CAC?
Yes, if founder time is a real input to acquisition. If you spend 10 hours a week on content and community, put a fair hourly value on it and add it to spend. Leaving it out makes organic look free, and it is not. The number will be higher and less flattering, but it will tell you the truth when you hire someone to replace those hours.
How often should I calculate blended CAC?
Monthly is what I use. Weekly is too noisy for most apps because organic traffic and app store approvals move in lumps. Track the monthly number on a simple chart and watch the trend, not the point. A single bad month is noise. Three rising months in a row is a problem with either product, creative, or channel mix.