Question 1

How much does GPT-5.1 cost?

Accepted Answer

GPT-5.1 costs $1.25 per 1 million input tokens and $10 per 1 million output tokens. This pricing is set by OpenAI.

Question 2

What tokenizer does GPT-5.1 use?

Accepted Answer

GPT-5.1 uses the o200k_base tokenizer. This is OpenAI's latest tokenizer, optimized for efficiency with a vocabulary of ~200,000 tokens.

Question 3

What is GPT-5.1's context window?

Accepted Answer

GPT-5.1 supports a context window of 400K tokens (400,000 tokens). The maximum output length is 16K tokens.

Question 4

How does GPT-5.1 compare to other models?

Accepted Answer

You can compare GPT-5.1's pricing and capabilities against other LLMs in the comparison table above, or visit the full pricing page for a side-by-side view of all models.

Question 5

How do I count tokens for GPT-5.1?

Accepted Answer

Use the token counter at the top of this page or visit the homepage calculator. Paste your text and it will show the exact token count and cost for GPT-5.1 using the o200k_base tokenizer.

GPT-5.1 Token Counter & Pricing

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Related Models

Model	Input / 1M	Output / 1M	Context	Max Output
GPT-5.1	$1.25	$10	400K	16K
GPT-5	$1.25	$10	400K	16K
Gemini 2.5 Pro	$1.25	$10	1.0M	66K
Nova 2.0 Pro Reasoning	$1.25	$10	128K	33K