Check the numbers before you ship the prompt.

Free tools for developers who work with AI APIs. Estimate costs, count tokens and clean up JSON. Everything runs in your browser.

• LLM API Cost CalculatorEstimate per-request, daily, monthly and yearly API spend from token counts and prices you enter.
• LLM Token CounterCount characters and words and get an approximate token estimate for any text.
• JSON Formatter and ValidatorFormat, minify and validate JSON with clear syntax error messages.

Guides

• How to Estimate LLM API CostsA step-by-step method for turning token counts and request volume into a monthly budget.
• How Tokenization WorksWhat tokens are, why counts differ between models, and why it matters for limits and cost.
• How to Format and Validate JSONThe rules of JSON, the most common errors and how to fix them.