LLM Tools
Context Window Calculator
See how much of a model's context window your prompt is using.
Usage
3.5%
Total tokens
4,500
Remaining tokens
123,500
Remaining
96.5%
Within limit. Practical usable context depends on the model and application — high usage isn't automatically unsafe, but leaves less room for output and follow-up turns.
How it works
A model's context window is the maximum number of tokens it can consider at once — covering the system prompt, user input, conversation history, retrieved context, and any tool/function definitions combined.
Formula
total = system + user + conversation + retrieved + tools
usage % = (total / context limit) × 100Frequently asked questions
Is using 80% of the context window always risky?
No — there's no universal threshold. Practical usable context depends on the model and how much room the application needs for output and subsequent turns.
What happens if I go over the limit?
Behavior varies by provider, but requests that exceed the context limit are typically truncated or rejected outright. Check the specific model's documentation.