Before building our AI Runway Calculator, we checked two existing AI API cost calculators directly and looked into a question we couldn't find good sourcing for.
A total, but never a timeline
We checked buttercloud.com's AI API cost calculator directly — it shows monthly cost, cost per 1,000 requests, and annual cost, all projected forward from your usage. We checked yourgpt.ai's LLM pricing calculator too — same shape: per-call and total cost, nothing else. Neither tells you the thing you actually want to know when you set a budget: how many days will this last? That's the entire premise of this tool — enter a budget and your usage pattern, and the headline number is runway in days, not a cost total.
Why we didn't build a Claude Pro/Max message counter
We looked for official numbers on how many messages Claude Pro or Max plans allow in the 5-hour window. Anthropic's own support documentation only describes Max 5x and Max 20x as multiples of the Pro plan's usage — it does not publish a fixed message count, because actual usage depends on message length, model, and complexity. Plenty of blog posts online state specific numbers anyway. We didn't want to build a tool around figures the source itself won't confirm, so this calculator covers pay-as-you-go API usage instead, where OpenAI, Anthropic, and Google all publish exact per-token pricing we can verify directly.
Prompt caching, handled the way Anthropic's own docs define it
We checked buttercloud.com's disclaimer directly — it explicitly excludes caching from its estimate. This calculator includes an optional toggle instead: when enabled, input token cost drops to 0.1× the standard rate, matching Anthropic's own published cache-hit pricing (a cache hit costs 10% of the standard input price). Toggle it on for Claude Opus 5 at our default settings and the cost per request drops from $0.0175 to $0.013 — a difference you can see reflected immediately in the runway number.
