Free browser tool

Context Packer

A context window calculator for planning what fills the prompt: system instructions, history, RAG evidence, examples, memory, and the answer space you need to reserve.

Key facts

Context Packer

  • The budget bar includes both prompt input and reserved output because both consume context-window space.
  • System instructions, conversation history, RAG evidence, examples, memory, and output reserve are tracked separately.
  • Over-budget plans should be fixed by selection, reranking, compression, or memory tiering before generation.
  • The calculator runs locally in the browser and does not transmit entered token budgets.

Budget inputs

Packed window

Used 0
Remaining 0
Window 0

Budget fits.

System instructions 0
Conversation history 0
RAG / evidence 0
Examples 0
Memory 0
Reserved output 0
Remaining 0

Use token estimates from the Token Counter or a model-specific tokenizer. This tool plans allocation; it does not tokenize text.

FAQ

What is a context packer?

A context packer is a planning aid for assigning a context-window budget across instructions, history, retrieved evidence, examples, memory, and reserved output.

Does the context packer send anything to a server?

No. It is a browser-only calculator. The numbers stay in the page and there is no backend.

Why is reserved output included in the bar?

The model answer consumes the same context window as the prompt. Reserving output space makes the budget realistic before generation starts.

How should I use the over-budget warning?

Reduce low-signal history, rerank retrieved passages, compress evidence with provenance, or move stable facts to memory before sending the prompt.