What is the context window of OpenAI: GPT-5.1-Codex-Max?

OpenAI: GPT-5.1-Codex-Max supports a context window of 400K tokens.

Is OpenAI: GPT-5.1-Codex-Max free to use?

OpenAI: GPT-5.1-Codex-Max is a paid model. It costs $1.25 per million input tokens and $10.00 per million output tokens.

How is LLM API pricing calculated?

LLM pricing has two components: input tokens (everything you send) and output tokens (what the model generates). Total cost = (prompt tokens × input rate + output tokens × output rate) / 1,000,000 × number of requests.

OpenAI: GPT-5.1-Codex-Max API Pricing — $1.25 Input / $10.00 Output per 1M Tokens

Q: How much does OpenAI: GPT-5.1-Codex-Max cost?

OpenAI: GPT-5.1-Codex-Max costs $1.25 per million input tokens and $10.00 per million output tokens via OpenRouter. Pricing was last updated Oct 29, 2026.

OpenAI: GPT-5.1-Codex-Max by OpenAI — $1.25 input / $10.00 output per 1M tokens via OpenRouter. Context: 400K tokens. Pricing last updated Oct 29, 2026.

Input / 1M tokens

$1.25

Output / 1M tokens

$10.00

Provider

OpenAI

Context window

400K tokens

Via

OpenRouter

Cost at common usage volumes

Usage	Daily	Monthly
Chatbot (100/day)	$1.31	$39.38
Small app (1K/day)	$6.25	$187.50
Mid-scale (10K/day)	$75.00	$2250.00
Large scale (100K/day)	$1625.00	$48750.00

Model ID: openai/gpt-5.1-codex-max
Data source: OpenRouter public API — updated Oct 29, 2026.

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About OpenAI: GPT-5.1-Codex-Max

OpenAI: GPT-5.1-Codex-Max is an LLM developed by OpenAI. Input costs $1.25 per million tokens and output costs $10.00 per million tokens via OpenRouter. It supports a context window of 400K tokens.

Pricing Details

Via the OpenRouter API:

Input tokens: $1.25 per 1 million tokens
Output tokens: $10.00 per 1 million tokens

A token is roughly 0.75 words. For context: a typical user message of 100 words is approximately 133 tokens; a 500-word system prompt is about 650 tokens.

How Much Does OpenAI: GPT-5.1-Codex-Max Cost?

For a typical chatbot application (1,000 requests/day, 1,000 prompt tokens and 500 output tokens per request):

Daily cost: $6.2500
Monthly cost: $187.500

Accessing OpenAI: GPT-5.1-Codex-Max via OpenRouter

OpenRouter provides a unified API for 200+ LLMs including OpenAI: GPT-5.1-Codex-Max. You can use it with any OpenAI-compatible SDK by setting the base URL to https://openrouter.ai/api/v1 and using your OpenRouter API key. The model ID is openai/gpt-5.1-codex-max.

Compare OpenAI: GPT-5.1-Codex-Max with Other Models

Use the AI Model Cost Comparison tool to compare OpenAI: GPT-5.1-Codex-Max against GPT-4o, Claude 3.5 Sonnet, Gemini 1.5 Pro, or any other model side by side. Or use the LLM API Cost Calculator to browse all 456+ models sorted by cost for your specific usage.

Frequently Asked Questions

Yes. OpenAI: GPT-5.1-Codex-Max is available on OpenRouter with the model ID openai/gpt-5.1-codex-max. OpenRouter provides a unified API compatible with OpenAI's SDK format.