Prompt Token Budgeter
Estimate token usage budget across system/user/assistant messages and reserve headroom for responses (approximation).
Last reviewed by the Radiatus Cloud team
Output
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Budget tokens across a conversation
A model request has a fixed token budget shared between the system prompt, user input, conversation history and the response, and planning it prevents overruns. This tool estimates token usage across system, user and assistant messages and reserves headroom for the reply.
Why budgeting tokens matters
Everything in a request competes for the same context window: the system prompt, the running conversation history, the current input, and crucially the space the model needs to actually respond. If the input fills the window, there is no room for a reply, or the model truncates. Budgeting the tokens, seeing how much each part uses and reserving headroom for the output, prevents that failure. It is especially important for long conversations, where history grows until it must be trimmed. Planning the budget shows when and what to trim before a request fails rather than after.
Leave room to reply
The tool runs entirely in your browser, so nothing you paste, prompts, outputs or documents, is uploaded, which matters when the input is sensitive AI data or your own content.
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Frequently Asked Questions
Why budget tokens across a request?
Because the system prompt, history, input and the response all share one context window. Without budgeting, input can fill the window leaving no room to reply.
What is headroom for the reply?
Reserved space in the context window for the model’s output. If input consumes everything, the model cannot respond fully or truncates.
Why does conversation history matter?
Because it grows with every turn, consuming more of the window until it must be trimmed. Budgeting shows when and what to trim.
What does the budgeter estimate?
How many tokens the system, user and assistant messages use, and whether enough headroom remains for the response.
Is my input uploaded?
No. The estimate runs entirely in your browser.
Privacy & Security
Processed locally in your browser. No prompts are sent to any server.
How to Use
Enter message sizes and model context window to estimate a safe response budget.
Disclaimer: This tool is provided "as is" without warranty of any kind. Results are for educational and utility purposes.
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