Free Browser Tool
Claude Context Window Planner
Allocate a Claude context window across instructions, tools, history, retrieval, working notes, and output reserve using current published model window sizes.
Used
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Remaining
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Window
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How to use it
- Choose the Claude model you plan to use.
- Enter estimated token budgets for instructions, tools, history, retrieval, notes, and output reserve.
- Review the live window bar and warnings.
- Copy or download the resulting context plan.
Why this tool exists
Claude context work often fails because teams reason from rough vibes instead of a visible budget. This tool makes the tradeoff explicit while keeping all inputs local to your browser.
Treat the output as a planning estimate. For production routing, pair it with current Anthropic docs, real usage telemetry, and token counting against the exact model you call.
FAQ
Does this planner count tokens from raw text?
No. It plans with token estimates you enter. For exact counts, use Anthropic token counting against the model you will call.
Is any prompt or document sent to a server?
No. The planner runs entirely in your browser and stores nothing remotely.
Why is output reserve included in the window?
Anthropic context-window docs describe the context window as including the response itself, so planned output needs budget.
Sources Used
- Models overview, Claude Platform Docs. Accessed 2026-07-06. Current model comparison, including context-window and output limits listed by Anthropic.
- Context windows, Claude Platform Docs. Accessed 2026-07-06. Official context-window behavior, token accumulation, extended thinking and tool-use accounting, and compaction guidance.
- Token counting, Claude Platform Docs. Accessed 2026-07-06. Official endpoint guidance for estimating input tokens, costs, rate limits, and model routing.