AI & LLM
Token, cost & context tools for LLMs
GPT Context Window Checker — Does Your Prompt Fit GPT-5.5?
GPT-5.5 has a 1,050,000-token context window — one of the largest available as of 2026-07-03. The context window is the total tokens the model can process at once: your system prompt + conversation history + user message + model response all count against this limit. Note that the max context window (1,050,000 tokens) and the max output (128,000 tokens) are different limits — the output budget is carved out of the total window. With 32,000 tokens reserved for output, the usable input space is 1,018,000 tokens. An 800,000-token prompt fits within that limit. Paste your prompt to check whether it fits before sending to the API.
GPT-5.5 context window: 1,050,000 tokens
- GPT-5.5 max output: 128,000 tokens (separate limit — NOT the same as context window)
- Usable input (1,050,000 − 32,000 reserved output): 1,018,000 tokens
- Example check: 800,000-token prompt → FITS
- Data as of 2026-07-03
Frequently asked questions
What is the context window of GPT-5.5?
GPT-5.5 has a 1,050,000-token context window (≈ 1.1M tokens). This includes all tokens: system prompt, conversation history, user message, and the model's response. The maximum output per response is 128,000 tokens — a separate, smaller limit. Data as of 2026-07-03.
What is the difference between the context window and max output?
The context window is the total token budget for one API call: input (prompt + history) + output (response) combined must fit within it. The max output is a separate hard limit on how many tokens the model can generate in a single response. For GPT-5.5: context window 1,050,000 tokens, max output 128,000 tokens. A prompt of 922,000 tokens would leave exactly 128,000 tokens of output space.