Context Window Calculator
Check if your text fits in different AI model context windows. Get instant recommendations.
Understanding Context Windows
The context window is the maximum amount of text (in tokens) an AI model can process at once, including both your input and its response.
| Model | Context Window | Best For |
|---|---|---|
| GPT-4o | 128,000 tokens (~96K words) | Long documents, extensive chat history |
| GPT-4o Mini | 128,000 tokens (~96K words) | Same as GPT-4o, but faster and cheaper |
| Claude 3 Opus | 200,000 tokens (~150K words) | Very long documents, entire codebases |
| Claude 3 Sonnet | 200,000 tokens (~150K words) | Balanced performance for long content |
| Claude 3 Haiku | 200,000 tokens (~150K words) | Fast processing of large documents |
| GPT-3.5 Turbo | 16,385 tokens (~12K words) | Shorter conversations, quick tasks |
Tips for Working with Context Windows
✂️ When Your Content is Too Large:
- Chunk your content: Split into smaller sections and process separately
- Summarize first: Ask AI to summarize, then work with the summary
- Use a larger model: Switch to Claude 3 (200K tokens) for bigger context
- Extract key sections: Only include relevant parts of your document
💡 Context Window Best Practices:
- Leave room for output: Reserve 20-30% of context for the AI's response
- System prompts count: Your instructions eat into the available space
- Chat history adds up: Each message in a conversation uses tokens
- Code is token-heavy: Programming languages use more tokens per character
Common Context Window Examples
✅ Fits in all models
✅ Fits in GPT-4o, Claude 3, ❌ Too large for GPT-3.5
✅ Fits in GPT-4o, Claude 3
✅ Only fits in Claude 3 (200K context)
Frequently Asked Questions
What is a context window in AI?
A context window is the maximum amount of text (measured in tokens) that an AI model can process in a single request, including both your input and its response. For example, GPT-4o has a 128,000 token context window, which equals roughly 96,000 words or 300 pages of text.
Which AI model has the largest context window?
Claude 3 models (Opus, Sonnet, Haiku) have the largest context window at 200,000 tokens (~150,000 words). This is larger than GPT-4o's 128,000 tokens. Claude can process entire books, large codebases, or extensive chat histories in a single request.
How many pages can GPT-4 process?
GPT-4o can process approximately 300 pages of text (assuming 400 words per page) in its 128,000 token context window. However, you should reserve 20-30% for the response, so realistically about 200-250 pages of input is safe.
What happens if I exceed the context window?
If your input exceeds the context window, the API will return an error and refuse to process the request. You'll need to either: (1) Shorten your input, (2) Split into chunks and process separately, (3) Use a model with a larger context like Claude 3, or (4) Summarize parts of your content first.
Do I need to count system prompts in the context?
Yes! Your system prompt, user message, previous conversation history, and the expected response ALL count toward the context limit. A typical system prompt uses 50-200 tokens. Always leave room for the AI's response when planning your input.
How do I reduce context usage?
To reduce context: (1) Summarize previous conversation turns instead of including full history, (2) Remove unnecessary formatting and whitespace, (3) Extract only relevant sections from documents, (4) Use token-efficient prompting, (5) Split large documents into logical chunks.
Is a larger context window always better?
Not always. Larger contexts can be slower and more expensive. GPT-4o with 128K tokens costs more to use than GPT-3.5 with 16K tokens. Also, models may lose focus with very long contexts ("lost in the middle" problem). Use the smallest context that fits your needs.