GPT API Cost Calculator accuracy and testing

Formula source

• Cost per call equals prompt token cost plus completion token cost. Daily cost multiplies cost per call by calls per day. Monthly cost multiplies daily cost by days per month, while monthly token totals show expected billable volume.

Test cases

Known limitations

• This page documents the checked-in calculator logic and does not certify results for every real-world edge case.
• Use the result as a planning estimate unless the calculator page states a stricter purpose.

Assumptions

• Prices are entered manually and are not fetched from any provider.
• Each call uses the same average prompt and completion token counts.
• The estimate excludes retries, caching discounts, storage, fine-tuning, taxes, and non-token fees.
• Calculations are deterministic and run locally.

Unit handling

• Model Pricing Preset accepts one of the configured options.
• Prompt Tokens accepts values in tokens/call.
• Completion Tokens accepts values in tokens/call.
• Prompt Price Per Million accepts values in $/1M tokens.
• Completion Price Per Million accepts values in $/1M tokens.
• Calls Per Day accepts values in calls/day.
• Days Per Month accepts values in days.
• Daily Cost is displayed as currency.
• Monthly Cost is displayed as currency.
• Cost Per Call is displayed as currency.
• Monthly Input Tokens is displayed in tokens.
• Monthly Output Tokens is displayed in tokens.

Rounding rules

• Number displays use up to 2 decimal places in the calculator UI.
• Currency outputs are displayed with standard US dollar formatting.
• Input precision follows configured step values where provided.

Version history

Change log