AI Free-Tier Cost Limit Calculator

A free calculator for founders of AI products who need to set a free-tier usage limit. Enter your own free-to-paid conversion rate, how long free users stay on free, the cost of one free task, and the margin a converted user brings in each month. The calculator gives the most tasks a free user can run each month, and checks the cap you have today. It runs in your browser; nothing you enter is sent anywhere.

How it works

A free tier is paid for by the free users who convert. Budget per free user = conversion rate × margin a month per converted user × months of margin you allow the free tier. Spread that over the months a free user stays on free, take off any other cost per free user, and divide by the cost of one task, the share of free users active in a month and the share of the cap they use. The result, rounded down, is the most tasks per active free user a month your numbers can afford: a ceiling, not a recommended setting.

• The conversion rate is the share of free sign-ups who ever pay, over their whole time on free, not per month.
• Keep the months of margin you allow the free tier separate from your CAC payback, or the free tier takes the whole payback window.
• The calculator also shows the limit at half and one and a half times your conversion rate, AAJ's choice of what-ifs, because conversion is the figure most founders are least sure of.
• Every input is yours. There are no benchmarks in it.

Why I built it this way

Free tiers on AI products are usually set by feel: a round number of messages, or whatever a competitor offers. Then a few heavy free users run up an inference bill nobody planned for. The honest way to set the limit starts from what free users are worth to you: how many convert, and what those customers bring in.

Limits

• The cap assumes conversion stays the same whatever the cap. A tighter cap can raise or lower conversion; only a test will tell you which.
• It uses one cost per task. If free users mostly run your most expensive task, use that task's cost.

For the whole plan, with price, routing, overage and the margin when usage spikes, use the AI Inference Cost Modeler, which runs the same engine.

Run this in your agent

The free AAJ agent skill AI Inference Cost & Usage Pricing does this job inside a coding agent, on your own data. Install it with npx skills add sarojkjha/aaj-marketing-skills --skill ai-inference-pricing.

Using Claude or ChatGPT instead? Add the AAJ engines as a custom connector, with no install: https://aaj-engines-mcp.sarojkjha10.workers.dev/mcp