LLM Context Window Calculator
Visualize how much of each AI model's context window your prompt or document uses across leading LLMs.
Paste your prompt, codebase, or document to check how much of each model's context window it consumes and what a full-context call costs.
Claude Opus 5.5
Anthropic · 1.0M window · $4/1M in
Claude Sonnet 5.5
Anthropic · 1.0M window · $2/1M in
Claude Haiku 5.5
Anthropic · 200K window · $0.1/1M in
Claude Fable 5.1
Anthropic · 1.0M window · $10/1M in
gpt-6-astra
OpenAI · 1.0M window · $10/1M in
gpt-6.1-sol
OpenAI · 1.0M window · $2/1M in
gpt-6-luna
OpenAI · 400K window · $0.1/1M in
gemini-4-argon
Google · 2.0M window · $2/1M in
gemini-3.8-flash
Google · 1.0M window · $0.75/1M in
gemini-3.1-pro-preview
Google · 2.0M window · $2/1M in
gemini-3.1-flash-lite
Google · 1.0M window · $0.25/1M in
Prices & context windows checked on 2026-10-16 against official Anthropic, OpenAI, and Google Gemini documentation.
Advertisement
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 leading LLMs (sourced from src/data/ai-models.ts, checked 2026-10-16), showing percentage used, tokens remaining, and long-context pricing thresholds.
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, DeepSeek) or view all.
- Inspect visual capacity gauges showing percentage of context filled and tokens remaining.
- Identify which models can comfortably handle your document payload and whether long-context tier pricing applies.
Worked Calculation Example
Frequently Asked Questions
What is an LLM context window?
A context window is the total token capacity an AI model can process in a single request — including system instructions, conversation history, retrieved documents, and the generated output.
What happens if a prompt exceeds the context window?
If your input tokens plus max output tokens exceed the model's context limit, the API returns a 400 error (such as context_length_exceeded) and rejects the request.
Which LLM has the largest context window in October 2026?
Among flagship models in our verified dataset (checked 2026-10-16), Google's Gemini 2.5 Pro and Gemini 2.5 Flash offer a 1,000,000-token standard context window (with Claude Sonnet 4 offering 200K standard / 1M beta tier and GPT-5 offering 400K).
Which AI model has the largest context window?
Among flagship models in our verified dataset, Google's Gemini 2.5 Pro offers a 1,000,000 token context window, with Claude Sonnet 4 offering 200K standard / 1M beta tier and GPT-5 offering 400K.
Related Tools & Guides
Related Tools
All Ai ToolsAI Token Counter & Cost Calculator
Estimate token count and API costs across OpenAI, Anthropic, Google, and DeepSeek language models.
AI API Budget Calculator
Project monthly and annual AI API costs across OpenAI, Anthropic, Google, and Groq based on your request volume.
Reading Time Calculator
Calculate accurate reading and speaking times for your text.