Context Overflow Calculator
Determine whether your prompt and history exceed a model's maximum context window.
About Context Overflow Calculator
Context overflow occurs when the sum of prompt tokens, conversation history, and reserved completion tokens exceeds the model's maximum context window. When overflow happens, you must truncate history, summarize context, or switch to a model with a larger context window.
Formula
Overflow Check
overflow = max(prompt + history + reserved - max_context, 0)
- max_context
- Model's maximum context window in tokens
Worked example
With the default values below, Context Overflow Calculator returns Overflow Tokens of 616. Change any input above and every figure here is recalculated in your browser.
Inputs used
- Prompt Tokensminimum 0
- 3,000
- History/Context Tokensminimum 0
- 12,000
- Reserved for Completionminimum 0
- 2,000
- Max Context Windowminimum 1
- 16,384
Results
- Overflow Tokens
- 616
- Context Utilization
- 103.8%
- Total Tokens Needed
- 17,000
Step by step
- 1Total tokens needed= 17000
- 2Overflow= 616 tokens over
Assumptions and limits
- The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
- In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
- Figures are rounded for display to 1 decimal place, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.
Frequently Asked Questions
What happens when context overflows?
Most APIs return an error. Some frameworks silently truncate the oldest messages. Either way, important context is lost, potentially degrading response quality.
How can I avoid overflow?
Implement sliding window history, summarize old messages, use RAG to retrieve only relevant context, or upgrade to a model with a larger context window.