AI Context Window Calculator
See how much of a model context window your prompt uses and what fits
Used to estimate how many items of this size fit.
Token counts are estimates; reserve headroom for the model response.
About AI Context Window Calculator
The AI context window calculator shows how much of a model’s context window your prompt consumes and how much room remains. Pick a model — the window sizes for popular AI models are built in — or enter a custom window, then set your system prompt tokens, input/conversation tokens and the output tokens you reserve for the response.
A usage bar visualizes the split between system, input, reserved output and free space, with exact used and remaining counts. Enter the typical token size of a document or message and the calculator tells you how many more items of that size still fit — or by how many tokens you are over the limit.
It answers the everyday RAG and chatbot questions: how many support articles fit alongside the system prompt, or when a conversation history must be trimmed. The tool is free and instant; token figures are estimates, so keep sensible headroom for the model’s reply.
How to use AI Context Window Calculator
- Select a model to load its context window, or enter a custom window size in tokens.
- Enter your system prompt tokens and the input or conversation tokens.
- Set the output tokens you want to reserve for the model’s response.
- Optionally enter the tokens per document or message to see how many items fit.
- Read the usage bar, the used and remaining counts, and the fit or over-limit verdict.