What is a context window?

A context window is the maximum number of tokens an LLM can process in a single request. Tokens include both your input prompt and the model's response. Different models have different context sizes.

Why does context window size matter?

Larger context windows allow you to provide more context (documents, conversation history, examples) to the model, improving quality but potentially increasing cost. If you exceed the window, your input will be truncated.

How do I calculate my token usage?

Enter the number of tokens in your input prompt, plus the expected number of tokens in the model's output. This calculator shows the percentage of context used and remaining tokens available.

Context Window Calculator

Enter your model and token usage to see how much context you have left. Prevents token overflow errors.

Model:

Tokens Used (Prompt + Response):

Max Output Tokens Reserved:

Context Window

128,000

Tokens Used

1,000

Reserved for Output

500

Remaining Available

126,500

Context Usage:

Safety Check:

✓ Safe to proceed

How This Works

Context Window: Total tokens the model can handle in one request.

Tokens Used: Your input prompt size + previous response tokens.

Reserved for Output: Tokens you want to save for the model's response.

Remaining Available: Context - Tokens Used - Reserved = available for new content.

Safety Margin: We recommend keeping 10-15% of context as buffer for safety.

How to Use

Select your model – Choose from GPT-4, Claude, Llama, Gemini, and more
Enter tokens used – How many tokens your prompt will consume
Set output tokens – Expected tokens for the model response
Check results – See percentage used and remaining tokens

Why Check Context Windows?

Prevent requests that exceed model context limits
Plan for long-form content analysis and generation
Compare context sizes between different LLM models
Optimize prompt structure to fit within limits
Avoid token overflow errors in production

Related Tools

Token Counter – Count tokens in your text
Prompt Cost Calculator – Estimate API costs
Temperature & Top-K Explainer – Understand sampling
Prompt Template Generator – Create structured prompts