LLM Context Window Calculator
See if your system, context and user messages fit the model window.
Messages
Max output: 16,384
Context budget
Estimating while the tokenizer loads
Fits — 126,962 tokens left after reserving 1,024 for the reply.
Same prompt on other models
- GPT-4o0.0% of 128,000
- GPT-4o mini0.0% of 128,000
- GPT-4.10.0% of 1,047,576
- GPT-4.1 mini0.0% of 1,047,576
- o30.0% of 200,000
- GPT-4 Turbo0.0% of 128,000
- GPT-3.5 Turbo0.1% of 16,385
- Claude Sonnet0.0% of 200,000
- Claude Haiku0.0% of 200,000
- Claude Opus0.0% of 200,000
- Gemini Flash0.0% of 1,048,576
- Gemini Pro0.0% of 1,048,576
- Llama 3.3 70B0.0% of 128,000
- Mistral Large0.0% of 131,072
About the LLM Context Window Calculator
Break a request into system prompt, retrieved context and user message, add realistic chat overhead, reserve room for the reply and instantly see whether the request fits GPT, Claude, Gemini, Llama or Mistral context windows.
Examples
RAG request
system + 8 chunks + questionOutput
12,480 / 128,000 tokens — fitsKeyboard shortcuts
- Copy the main outputCtrl / ⌘ + Shift + C
- Download the resultCtrl / ⌘ + S
- Share this toolCtrl / ⌘ + Shift + S
- Reset the inputsAlt + R
- Open the tool search paletteCtrl / ⌘ + K
Related tools
AI Token Counter
AI & LLM
Count exact LLM tokens for GPT, Claude and Gemini prompts.
LLM API Cost Calculator
AI & LLM
Estimate GPT, Claude and Gemini API spend per call and per month.
AI PII & Secret Redactor
AI & LLM
Strip emails, keys, tokens and personal data before prompting an LLM.
AI Tool Schema Builder
AI & LLM
Build function-calling schemas for OpenAI, Claude, Gemini, MCP and the AI SDK.
JSONL ↔ JSON Converter
AI & LLM
Convert JSON Lines to a JSON array and back again.
JSONL Formatter
AI & LLM
Pretty-print, minify, sort and deduplicate JSON Lines files.
Frequently asked questions
Version 1.0.0 · Updated 2026-08-14 · Runs entirely in your browser