Generative AI API Rate-Limit Budget Calculator

Map product usage assumptions into concrete API requirements by sizing the sustained request rate, token throughput, monthly bill, and variance against your target budget so you can provision hosted generative AI endpoints with confidence.

Unique daily active users you expect to generate completions on a typical day.
Average number of completions or generations each active user triggers per day.
Combined prompt and completion tokens consumed per API call (input + output).
Provider charge for each 1,000 tokens in the selected model tier.
Defaults to no cap. Enter a monthly budget ceiling to highlight overages or leftover headroom.
Defaults to 30 days. Adjust for shorter billing cycles, weekend throttling, or maintenance downtime.

Estimates only. Confirm pricing and throttling rules with your API vendor before scaling production workloads.

Examples

  • 12,000 daily users, 4 requests each, 1,800 tokens per call, $0.002 per 1K tokens, $5,500 budget, 30 days ⇒ Rate limit 33.33 requests/min (0.56 rps); 60,000 tokens/min; 86,400,000 tokens/day; 2,592,000,000 tokens/month; $5,184.00 USD spend; $0.43 USD per user; $316.00 USD under budget.
  • 3,500 daily users, 2.5 requests each, 900 tokens per call, $0.0013 per 1K tokens, no budget, 31 days ⇒ Rate limit 6.08 requests/min (0.10 rps); 5,469 tokens/min; 7,875,000 tokens/day; 244,125,000 tokens/month; $317.36 USD spend; $0.09 USD per user.

FAQ

How can I model bursts during business hours?

Increase the requests-per-user input to reflect peak-hour intensity or shorten the billing days to the number of heavy-usage days you want to provision for when sizing sustained rate limits.

Does the token estimate include embeddings or moderation calls?

Enter the combined tokens for every API call you expect per request, or run the calculator separately for each model family and sum the resulting spend.

What if the provider charges different input and output rates?

Use a blended per-1K token price that weights the input and output rates by their average share of total tokens so the spend projection stays accurate.

Can I convert this to an annual budget?

Multiply the monthly spend result by 12 or by the number of months you plan to stay at this utilisation level, then layer on expected growth to build a forward-looking forecast.

Additional Information

  • Requests per minute divides total daily calls by 1,440 minutes, while requests per second highlights real-time concurrency requirements for throttling policies.
  • Token throughput multiplies the sustained request rate by the tokens per call to size TPM quotas, streaming limits, and autoscaling thresholds.
  • Monthly spend multiplies total monthly tokens by the per-1K token price, assuming consistent usage across the billing period and steady demand from weekdays to weekends.
  • Budget variance shows whether projected spend is over, under, or on target versus the optional monthly budget input, and the per-user figure contextualises cost allocations for finance teams.
  • Adjusting billing days lets you simulate partial-month deployments or staged rollouts without skewing rate-limit requirements.

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