GPT-5.1: token counter & pricing
OpenAI · exact (uses official tokenizer) · pricing as of 2026-05-31.
- Provider
- OpenAI
- API model ID
gpt-5.1- Context window
- 400,000 tokens
- Input price
- $1.25 per 1M tokens
- Output price
- $10.00 per 1M tokens
- Tokenizer accuracy
- exact (uses official tokenizer)
- Pricing as of
- 2026-05-31
Open the counter to count tokens for GPT-5.1 in real time.
What is GPT-5.1?
GPT-5.1 is OpenAI's first incremental update to the original GPT-5, same tokenizer and context window, slightly improved instruction-following and coding behavior. Priced identically to GPT-5 itself at $1.25 input / $10 output per 1M tokens.
If you've already tuned a workload on GPT-5 and just want the quality bump without changing your cost model, GPT-5.1 is the drop-in.
How tokens are counted here
Uses OpenAI's o200k_base tokenizer (shared across the whole GPT-5 family + GPT-4o). Counts run in your browser via js-tiktoken, your prompt never leaves your device. Exact.
Pricing notes
$1.25 input / $10 output per 1M. Cached input drops to $0.125/M (10% standard) with OpenAI prompt caching.
Single-tier pricing, no long-context surcharge above 128K input the way GPT-5.4 / GPT-5.5 charge. That makes GPT-5.1 attractive for workloads that frequently push past 128K context.
When to use GPT-5.1
- Stable production workloads already running on GPT-5, predictable cost, minor quality lift.
- Long-context inputs (>128K) where you want to avoid the GPT-5.4/5.5 long-context price jump.
- Cost-predictable agent loops where the single-tier price simplifies budget math.
When not to use it:
- New work. GPT-5.5 is the current flagship.
- Tasks where GPT-5.4 or higher measurably wins on your evals.
Common questions
How does GPT-5.1 differ from GPT-5.2?
GPT-5.2 is priced higher ($1.75/$14) and adds further reasoning improvements. If you're paying GPT-5.2's premium, you should be measuring it winning on something specific, otherwise GPT-5.1 is the cheaper rational default in this tier.
Same context window as GPT-5?
Yes, 400K. Same as the whole GPT-5 family.
Will GPT-5.1 be deprecated?
OpenAI hasn't announced a sunset. The historical pattern: predecessor minor versions stay on the API for 12-24 months past the next flagship.
Compare GPT-5.1 to other models
- GPT-5.5 (OpenAI, $5.00/$30.00)
- GPT-5.5 Pro (OpenAI, $30.00/$180.00)
- GPT-5.4 (OpenAI, $2.50/$15.00)
- GPT-5.4 Mini (OpenAI, $0.75/$4.50)
- GPT-5.4 Nano (OpenAI, $0.20/$1.25)
- GPT-5.4 Pro (OpenAI, $30.00/$180.00)
- GPT-5.3 (OpenAI, $1.75/$14.00)
- GPT-5.2 (OpenAI, $1.75/$14.00)
- GPT-5.2 Pro (OpenAI, $21.00/$168.00)
- GPT-5 (OpenAI, $1.25/$10.00)
- GPT-5 Mini (OpenAI, $0.25/$2.00)
- GPT-5 Nano (OpenAI, $0.05/$0.40)
- GPT-5 Pro (OpenAI, $15.00/$120.00)
- GPT-4.1 (OpenAI, $2.00/$8.00)
- GPT-4.1 Mini (OpenAI, $0.40/$1.60)
- GPT-4.1 Nano (OpenAI, $0.10/$0.40)
- o3 (OpenAI, $2.00/$8.00)
- o3-mini (OpenAI, $1.10/$4.40)
- o3-pro (OpenAI, $20.00/$80.00)
- o4-mini (OpenAI, $1.10/$4.40)
- GPT-4o (OpenAI, $2.50/$10.00)
- GPT-4o mini (OpenAI, $0.15/$0.60)
- GPT-4 Turbo (OpenAI, $10.00/$30.00)
- Gemini 2.5 Pro (Google, $1.25/$10.00)
- GLM-5.1 (zhipu, $1.40/$4.40)
- Claude Haiku 4.5 (Anthropic, $1.00/$5.00)