LLM Context Window Calculator
Visualize how much of each AI model's context window your prompt or document uses across 12+ LLMs.
Paste your text to visualize how much of each AI model's context window it uses. Uses a ~4 chars/token heuristic approximation.
GPT-4o
OpenAI · 128K context
GPT-4o mini
OpenAI · 128K context
GPT-4 Turbo
OpenAI · 128K context
GPT-3.5 Turbo
OpenAI · 16K context
Claude 3.5 Sonnet
Anthropic · 200K context
Claude 3 Opus
Anthropic · 200K context
Claude 3 Haiku
Anthropic · 200K context
Gemini 1.5 Pro
Google · 2M context
Gemini 1.5 Flash
Google · 1M context
Gemini 2.0 Flash
Google · 1M context
Llama 3.3 70B
Meta (via Groq) · 128K context
Mistral Large
Mistral · 128K context
Token counts are approximations using a character-based heuristic (~4 chars/token). Actual tokenization varies by model and may differ ±10–15%. For production use, implement the exact tokenizer (tiktoken for OpenAI, claude-tokenizer for Anthropic).
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How to use the Context Window Calculator
?Frequently Asked Questions
What is the LLM Context Window Calculator?
The Context Window Calculator visualizes how much of each major AI model's maximum context capacity is occupied by your input text. It compares capacities across 12+ leading LLMs, showing percentage used, tokens remaining, and threshold warnings.
Who is the LLM Context Window Calculator for?
Essential for prompt engineers, RAG (Retrieval-Augmented Generation) pipeline architects, long-document summarizers, and AI product managers.
How to Use the LLM Context Window Calculator
- Paste your prompt, context document, or system instructions into the text area.
- Filter models by provider (OpenAI, Anthropic, Google, Meta, Mistral) or view all.
- Inspect visual capacity gauges showing percentage of context filled and tokens remaining.
- Identify which models can comfortably handle your document payload.
Worked Calculation Example
Frequently Asked Questions
What is an LLM context window?
A context window is the total memory capacity of an AI model in a single request — including all system instructions, previous conversation history, retrieved documents, and the generated response.
What happens if a prompt exceeds the context window?
If your input tokens plus desired output tokens exceed the model's context limit, the API returns a 400 Bad Request error (e.g., context_length_exceeded) and refuses execution.
Which LLM has the largest context window in 2026?
Google's Gemini 1.5 Pro currently offers the largest commercial context window at 2,000,000 tokens (~1.5 million words), followed by Gemini Flash (1M) and Claude 3.5 Sonnet (200K).
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