Context Window Usage Calculator
See what percentage of a model's context window you're using.
Results update automatically as you type.
Result
15.6% of the context window used
20,000 tokens of 128,000 tokens · 108,000 tokens free
- Tokens used
- 20,000 tokens
- Context window
- 128,000 tokens
- Used
- 15.6%
- Remaining
- 108,000 tokens
Enter how many tokens you're sending and pick a model to see how much of its context window you're filling and how much room is left for retrieval, history and output.
How this is calculated
This calculator uses the tokens formulas described in our methodology. All figures are estimates for planning; verify current pricing with each provider before relying on them.
Worked example (defaults)
With the default inputs above, here is the result:
Result
15.6% of the context window used
20,000 tokens of 128,000 tokens · 108,000 tokens free
- Tokens used
- 20,000 tokens
- Context window
- 128,000 tokens
- Used
- 15.6%
- Remaining
- 108,000 tokens
Frequently asked questions
What is a context window?+
The maximum number of tokens (input + output) a model can consider at once. Exceeding it causes errors or truncation.
How full should I let it get?+
Leave headroom for the response. Very full contexts can also degrade quality ('lost in the middle').