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AiTechWorlds
AiTechWorlds
Measure your prompt against GPT, Claude, Gemini and Llama context windows and see if it fits.
100% in-browser. Token count uses the GPT (BPE) tokenizer (close for other models). "Reserve for output" sets aside room for the model's reply when checking if your prompt fits.
The Context Window Calculator counts your prompt's tokens and compares them against the context windows of popular models — GPT-4o, o3, Claude, Gemini, Llama, DeepSeek and Mistral — with a reserve for the model's output, so you can see exactly which models your prompt fits in.
Paste your prompt
Add the prompt or document to measure.
Set output reserve
Reserve tokens for the model's reply.
Compare
See per-model usage bars and whether it fits.
100% Private — No Server Required
All processing happens directly in your browser. No data is uploaded, stored, or transmitted to any server.
Last reviewed on June 24, 2026 by the AiTechWorlds Tools Team. All processing runs locally in your browser.
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