How many users a TPM/RPM rate limit can actually serve at once.
TPM and RPM are two ceilings, and only the lower one matters — raising the other is wasted effort. Forecast where traffic pushes you on the API cost forecast calculator, and size the tokens behind each call on the LLM token cost calculator.
Free rate-limit capacity calculator — turn a TPM and RPM API rate limit into the number of concurrent active users you can serve before requests get throttled.
Providers cap you on both tokens-per-minute (TPM) and requests-per-minute (RPM), and you hit whichever comes first. Small, frequent calls usually hit RPM; large-context calls hit TPM. Your real capacity is the lower of the two, so raising only the non-binding limit changes nothing.
Lift the binding limit — request a higher tier for whichever one caps you, batch or combine small requests to ease RPM, and trim prompt size to ease TPM. Caching repeated context and routing overflow to a second key or model also spreads load beyond a single limit.