AI API Token & Context Window Estimator

Estimate AI API input and output tokens, context-window usage, and potential model costs.

Business Calculators

AI API Token & Context Window Estimator

Estimate prompt and response tokens, context usage, and API costs using your own model pricing. No text is sent to a server by this calculator.

Input method

Prompt text (optional)Rough estimate: 1 token per 4 characters. Actual tokenization varies by model, language, and content.

Input tokens per requestIn text mode, this is estimated from your prompt when text is entered.

Expected output tokens per request

Model context window (tokens)Enter your model's documented context limit.

Number of requests

Input price (USD per 1M tokens)Example value only; check your provider's current rate.

Output price (USD per 1M tokens)Example value only; check your provider's current rate.

Formula: request cost = (input tokens × input price + output tokens × output price) ÷ 1,000,000; total cost = request cost × requests. Context usage = input + reserved output tokens. Actual usage and bills may differ due to tokenizer behavior, cached token pricing, tool calls, hidden reasoning tokens, system prompts, provider limits, and other fees. This estimator does not automatically fetch model pricing.