Prompt Cost Estimator — Calculate AI Prompt Token Expense
Use this free Prompt Cost Estimator to find out how much your AI prompt will cost before you send it to an API. Just paste your prompt text, select the model you are using, and set an expected output length — this tool instantly estimates both the token count and the estimated cost per execution. It helps developers, product managers, and founders plan and optimize prompt usage across LLMs such as GPT-4o, Claude, Gemini, and others. Knowing your prompt cost upfront helps you manage budgets and avoid surprises in AI billing.
How This Prompt Cost Estimator Works
When you interact with an LLM, both the prompt (input) and the response (output) consume tokens, and providers charge based on token usage. This estimator calculates the input token count of your prompt and combines it with the expected output tokens you enter. It then multiplies the total tokens by the selected model’s pricing formula to display your expected cost. This shared logic reflects real billing models used by major AI providers.
Example Calculation
For a customer support chatbot using GPT-4o Mini:
- Prompt: 200 tokens (system message + user question)
- Response: 300 tokens (assistant answer)
- Cost per interaction: ~$0.00033
- 1,000 conversations: ~$0.33
Frequently Asked Questions
How much does a GPT API call cost?
The cost varies by model and tokens. GPT-4o costs $0.005 per 1K input tokens and $0.015 per 1K output tokens. A typical 200-input + 300-output token request costs about $0.0055. GPT-4o Mini is much cheaper at $0.00033 per similar request.
How do I calculate prompt cost with output?
Multiply input tokens by input price, multiply output tokens by output price, then add them. For example: (200 input × $0.005) + (300 output × $0.015) = $0.001 + $0.0045 = $0.0055 per request. Use our calculator above for instant results.
Why does output cost more than input?
Output tokens cost 2-3× more than input because the model must generate each token sequentially, using more compute. Input is processed in parallel. For GPT-4o, output costs $0.015/1K vs $0.005/1K for input—a 3× difference.
How can I reduce my prompt costs?
To reduce costs: (1) Use cheaper models like GPT-4o Mini for simple tasks, (2) Set max_tokens to limit output length, (3) Optimize prompts to be concise, (4) Cache common responses, (5) Batch similar requests together.
What's the average cost per ChatGPT conversation?
A typical ChatGPT conversation averages $0.01-0.05 depending on length and model. Short Q&A (GPT-4o Mini) costs ~$0.001. Long technical discussions (GPT-4o) can cost $0.10-0.50. ChatGPT Plus ($20/month) becomes economical after ~400-2000 conversations.