Monthly AI Bill Forecaster

A forecast expressed as one number is a forecast that will be wrong, and being wrong by ten per cent in either direction is the normal outcome even when the model is sound. The reason to carry a band instead is that the two ends drive different decisions. The quiet figure is what you can commit to contractually. The busy figure is what your spend cap has to survive without taking the product down. A single central number answers neither question.

The band here is deliberately your own input rather than something computed for you. Request volumes across a user base are strongly skewed — a small fraction of users generate a large fraction of calls — and the shape of that skew is specific to your product. Nobody can hand you a distribution for it. What you can do is put a floor and a ceiling on it from what you have seen, and then check the ceiling against your rate limits rather than only against your budget, because the busy month is the one that discovers your tokens-per-minute cap.

The growth projection compounds users, not intensity. That is the conservative half of a forecast and the optimistic half of a budget: in practice per-user token consumption tends to climb as people learn what the feature can do and start pasting larger documents into it. If you want the pessimistic version, raise the input tokens per request along with the user count and watch how much faster month twelve moves. Cost per active user is the number worth tracking month to month — it is the one that tells you whether the product is getting more efficient or just larger.