Your monthly AI bill divided by active users.
Revenue per user is meaningless if AI cost per user is chasing it. This ratio is the health check. Price with margin on the AI SaaS margin calculator.
The AI Cost per Active User Calculator turns your total monthly AI spend and your number of monthly active users into a single number: how much AI actually costs you per active user each month. It divides spend by active users to give that per-user figure, and by comparing it against what you charge per user, it also reveals your unit economics — the gross margin, or loss, that each user generates after AI costs. The two main drivers are your API bill (a function of model choice, token volume, and request frequency) and how many users are genuinely active, since idle or free accounts inflate spend without spreading it across paying usage.
The key trade-off to watch is the gap between cost per user and revenue per user. A low per-user AI cost can still be unprofitable if a small share of power users consumes most of the tokens while the average dilutes the true picture, so track this figure as your user base and usage patterns shift rather than treating it as fixed. If AI cost per user approaches or exceeds what you charge, the practical levers are reducing tokens per request, choosing cheaper models for routine tasks, or adjusting pricing before growth scales the loss.
Monthly AI spend ÷ monthly active users. It's the core unit-economics metric for an AI product — it tells you whether each user is profitable once AI cost is counted.
Because AI usage grows as users engage more. A metric that looks fine at launch can quietly rise until AI cost approaches your price. Watching it monthly catches the trend early.