How API rate limits shape LLM cost and capacity

The quiet bottleneck

You can afford a model on paper and still miss SLOs if TPM or concurrency saturates. Capacity planning belongs next to the cost spreadsheet.

Convert every limit into an equivalent RPM for your token shape and latency. The lowest RPM wins—and that is your sustainable peak.

Once you know monthly requests at capacity, multiply by per-request cost. That is the budget you need if traffic fills the pipe.

No. They are starting points. Replace RPM/TPM with the numbers from your provider dashboard.