← All tools
Context Window Budget Planner
See how much of a model's context window your prompt actually uses. Paste your system prompt, history, and message — get estimated token counts and remaining budget. Everything runs in your browser.
0
System (est. tokens)
0
History (est. tokens)
0
Message (est. tokens)
0
Total used
0
Remaining
0% of context window used (estimate)
About this tool
Token counts here are estimates, not exact tokenizer output. Each provider uses its own tokenizer (tiktoken, Claude's BPE, SentencePiece), so this tool blends two common heuristics — characters ÷ 4 and words × 1.33 — and averages them. Expect real counts to differ by roughly 10–20%, especially for code, non-English text, or heavy punctuation. Use it for budgeting and sanity checks, not billing math.
Your prompts never leave the page — there is no server, no upload, and no tracking of tool inputs.
Found this useful?
113 free, browser-only tools by Yuvrajsinh Jadav — an engineer who ships production AI systems. No account, nothing sent anywhere.