Context Window Budget Calculator
Remaining context equals the supplied context limit minus instruction tokens, history tokens and output reserve. Count all relevant prompt material using your provider’s tokenization rules.
Formula & method
Remaining tokens = context limit − instructions − history − output reserve.Worked example
| Input | Value |
|---|---|
| Context-window token limit | 32,000 |
| Instruction and tool-definition tokens | 2,000 |
| Existing history and other input tokens | 12,000 |
| Reserved output tokens | 4,000 |
| Result | Value |
|---|---|
| Remaining input allowance | 14,000 tokens |
| Share already allocated | 56.25 % |
Compare scenarios
The first input changes while the other example inputs stay fixed. These are arithmetic scenarios, not forecasts.
| Compare scenarios | Context-window token limit | Remaining input allowance | Share already allocated |
|---|---|---|---|
| −20% | 25,600 | 7,600 tokens | 70.3125 % |
| Example | 32,000 | 14,000 tokens | 56.25 % |
| +20% | 38,400 | 20,400 tokens | 46.875 % |
Assumptions & limits
The limit is user-entered, not a current model specification. Providers can impose separate input or output ceilings and count tools, hidden instructions, multimodal content or reasoning differently. Leave extra room when the exact rendered prompt count is unknown.
Displayed results are rounded. Calculations use unrounded JavaScript numbers; small floating-point differences are possible.
Works in your browser
The interactive tool runs in a sandbox with network access blocked. ClearByte and the advertising scripts cannot read values inside it. Browser extensions and a compromised device remain outside this protection.
Sources & definitions
Method checked:
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