Context Window Usage Calculator

Find what percentage of a model's context window your prompt is using.

Inputs

Tokens Used

Max Context Window (tokens)

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Saved Scenarios

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Context Used

25.0%

Tokens Remaining

96,000

Spark says

How it's calculated

Formula

Usage\% = \dfrac{Tokens\ Used}{Max\ Context} \times 100

Max\ Context: — The model's maximum context window size, in tokens

What is the Context Window Usage Calculator?

Every LLM has a fixed maximum context window (the total tokens it can 'see' at once, including prompt, conversation history, and output) — this calculator shows how much headroom is left.

How to use it

1 Enter the tokens already used (prompt + conversation history).
2 Enter the model's maximum context window size.

Worked examples

32K used of a 128K context window

25% used, 96,000 tokens remaining.

Try it

Frequently asked questions

What happens if I exceed the context window?

Behavior varies by provider — some truncate the oldest content, some return an error, and some silently drop earlier context. Check your provider's specific handling.