AI Cost CalculatorDesigning an AI SaaS free tier without guessing
How to set an AI product free allowance using activation needs, heavy-user behavior, unit cost, abuse controls and a clear upgrade moment.
Free plans usually get designed with round numbers. Ten reports sounds neat. A hundred messages sounds generous. But neither number tells you whether a new user can reach the moment the product clicks - or whether a handful of people can burn through the month's budget before breakfast.
The allowance should come from how people use the product and what it costs you, not from what looks tidy on a pricing card.
Find the smallest complete experience
Ask how much someone needs to do before they can fairly judge the product. A document tool might need three files, because the first one goes on learning the interface. A support assistant might need enough chats to hit one tricky case. That complete experience is the floor for a useful free plan.
Don't spread the allowance thin across every feature just because the paid plan has them. Give free users a clear run at the main job. A narrow experience they can actually finish beats a dozen buttons that all run out just before they pay off.
Work out what an active free user costs
Add up the AI and hosting cost of that experience, including the failed tries and the onboarding prompts (which tend to be longer than normal use). Then multiply by the number of free signups you can realistically get - not just the ones you hope will pay.
That gives you a monthly acquisition budget you can weigh against expected paid revenue, the same way you'd weigh ad spend against new customers. Free usage isn't automatically wasteful - but it should have an owner and a reason.
Watch the heavy tail, not just the middle
Most free accounts cost next to nothing while a few run non-stop. The typical account won't warn you about those few. Look at your heaviest users specifically, and decide whether they're keen prospects, accidental loops, automated scripts, or deliberate abuse.
Put limits where the cost is actually created. A daily limit people can see is easier to understand than a hidden quota. And for the unusually expensive jobs, show the cost up front before someone kicks one off.
Make hitting the limit feel fair
The limit should land after someone's seen the value, not in the middle of their first win. Tell them what's left and what a paid plan changes. Don't dangle a vague "unlimited" and then quietly throttle them under a fair-use rule nobody published - clear limits build far more trust than generous words followed by a surprise block.
Free and paid users don't always need the same model. A cheaper model can be fine for a free preview, as long as the experience still represents the real thing. Just be honest when paying gets you better quality, more speed or more room to work.
Revisit the plan as the product changes
Prices drop, prompts grow, new tools add cost. Recalculate the allowance whenever the workflow changes much. Track conversion and the cost of both an active free user and a converted one, side by side. A cheap free plan that teaches nobody why to pay isn't efficient. A slightly pricier one that reliably creates informed buyers can be money well spent.