OpenAI · 400K context · updated 2026-10-02
Input · what you send
$30
per 1M tokens
Output · what it writes
$180
per 1M tokens
Previous generation. OpenAI's current replacement is GPT-6 Astra at $10 input / $50 output per 1M tokens.
55,556 tokens
333,333 tokens
For context: the cheapest model tracked here is GPT-6 Luna at $0.50/1M output tokens, and the most expensive is GPT-6 Astra at $50 — a 100× spread.Try your own budget in the calculator →
| Model | Input / 1M | Output / 1M | vs GPT-5.5 Pro (output) |
|---|---|---|---|
| GPT-6 Astra | $10 | $50 | 3.6× cheaper |
| Claude Fable 5.1 | $10 | $50 | 3.6× cheaper |
| Claude Opus 5 | $5 | $25 | 7.2× cheaper |
| Claude Opus 5.5 | $4 | $20 | 9× cheaper |
| GPT-6 Sol | $2 | $10 | 18× cheaper |
| Gemini 3.1 Pro | $2 | $12 | 15× cheaper |
| Claude Sonnet 5 | $2 | $10 | 18× cheaper |
| Claude Haiku 4.5 | $1 | $5 | 36× cheaper |
| Gemini 3.8 Flash | $0.75 | $3.75 | 48× cheaper |
| Gemini 3.5 Flash-Lite | $0.30 | $2.50 | 72× cheaper |
| GPT-6 Luna | $0.10 | $0.50 | 360× cheaper |
GPT-5.5 Pro supports a 400K token context window. That means in a single API call, you can send up to 400K tokens of input — including your prompt, system instructions, and any documents or code you want the model to process.
In practical terms, 400K tokens is approximately:
Compare all models' context windows on the context windows page.