OpenAI API Cost Calculator
Estimate your OpenAI API spend. Enter average token counts per request and volume to get per-request and monthly cost breakdowns for each model.
System prompt + user message
Model response length
| Model | Context | Input/1M | Output/1M | Per Request | Monthly |
|---|
Prices as of Q1 2025. Verify at platform.openai.com/pricing. Batch API offers 50% discount for non-realtime workloads. Prompt Caching reduces cost for repeated system prompts.
Frequently Asked Questions
Why are input and output tokens priced differently?▼
Output generation requires more compute than reading input. OpenAI charges output tokens 3–5x more than input tokens. For GPT-4o: input is $5/1M, output is $15/1M. Budget accordingly — especially for long responses.
What counts as an input token?▼
Everything sent to the API in one request: system prompt, conversation history, user message, and any function/tool definitions. Cached input (Prompt Caching) may be cheaper on supported models.
What is context window and why does it matter?▼
The context window is the max tokens per request (input + output combined). GPT-4o: 128K tokens. Exceeding the context window returns an error. Long conversation histories grow your input token count each turn.
How do I reduce OpenAI API costs?▼
Use GPT-4o Mini instead of GPT-4o for high-volume tasks (~33x cheaper). Cache system prompts with Prompt Caching. Limit conversation history tokens. Use streaming to display partial results faster. Batch non-realtime workloads with the Batch API (50% discount).
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