K-factor calculator
the K-factor is how many new users each user brings you. above 1 and growth compounds by itself. below 1, and it is almost always below 1, invites still help by multiplying every user you buy. that multiplier is the useful part.
this calculator needs javascript. the explanation below works without it.
The bit worth understanding
even a K well below 1 matters. at K of 0.4 every user you pay for turns into about 1.67 users once their invites and their invitees invites are counted, which is the same as cutting your cost per user by 40%.
that is the honest way to use this number. treat virality as a discount on acquisition, not as a substitute for it.
Why most invite features do nothing
they get built, buried in a settings menu, and never mentioned again. the invite has to appear at the moment the user is happiest with the product, which is right after something worked, not on a profile screen.
the other common failure is asking for a share with nothing in it for the person receiving it. an invite that offers the recipient something useful converts many times better than one that only helps the sender.
Numbers tell you what. They do not tell you what to do.
bring your real numbers to the breakdown call and leave with a plan for them. free, no pitch deck.
Common questions
How do I measure invites per user honestly?
across all users in a cohort, not just the ones who sent invites. dividing by only the senders produces a flattering number that overstates the effect several times over.
Does word of mouth count?
not in this calculation, because you cannot attribute it reliably. it shows up instead as organic installs, which is why blended CAC is usually lower than paid CAC. keep the two effects separate or you will count the same growth twice.
Other scale tools
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put in D1, D7 and D30 retention and your install rate, and see where your active users flatten out.
ScaleChurn to customer lifetime
convert monthly churn into how long an average customer stays, how many survive a year, and what cutting churn is worth.
ScaleFree trial to paid
work out revenue from trial starts, and the real cost of acquiring a paying customer once you account for trials that never convert.
ScaleApp store conversion
break your app store funnel into impressions, page views and installs, and find which step is leaking.
Bring one real growth problem. Leave with the fix.
the breakdown call is free. no pitch deck, no agency handoff.