GPT-5.1vsgpt-oss-120b
GPT-5.1 | gpt-oss-120b | |
|---|---|---|
| Specifications | ||
ParametersA rough measure of how big the model is. More parameters usually means more capable and more expensive to run, though it is a poor guide on its own — a smaller, newer model often beats a larger, older one. | — | 117B |
Context windowHow much text the model can hold in mind at once — your question, any documents you attach, the conversation so far, and its own reply. Go past it and the earliest part falls out of view. | — | 128k |
| API pricingUSD per 1M tokens · lower wins | ||
Input priceWhat you pay for everything you send the model — your question, plus any documents or earlier conversation you include with it. | $1.25 | — |
Output priceWhat you pay for the text the model writes back. It is normally the dearer half: producing an answer costs more than reading one. | $10.00 | — |
Cached input priceA reduced rate for text you send over and over. If every request starts with the same instructions or the same document, the provider keeps a copy ready and charges less to read it again. | $0.125 | — |
Cheapest inputLowest input rate across third-party providers, excluding the lab itself. The cheapest endpoint may run a quantised build or a shorter context — see "Available from" on the model page. | $1.25Azure | $0.03AkashML |
Cheapest outputLowest output rate across third-party providers, excluding the lab itself. May come from a different provider than the cheapest input. | $10.00Azure | $0.17AkashML |
| Benchmarks | ||
BullshitBench v2Nonsense detection — Given a confidently-worded but nonsensical prompt, does the AI spot that it makes no sense and push back — instead of playing along and inventing an answer? The score is how often it clearly called out the nonsense. Higher is better. | 25% | 11% |
SWE-Bench VerifiedCoding — Real coding tasks pulled from open-source projects — the AI has to find and fix actual bugs. A human-checked version of the original SWE-Bench. Higher is better. | 76.3% | 62.4% |
GPQA DiamondScience — Graduate-level science questions in biology, physics, and chemistry — hard enough that subject-matter PhDs score around 65%. Higher is better. | 88.1% | 80.1% |
| BenchmarksPublished by one model only | ||
Humanity's Last Exam · no toolsMultidisciplinary reasoning — Humanity's Last Exam — extremely hard expert questions across many subjects, written so you can't just look up the answer. “No tools” means the AI answers on its own. Higher is better. | — | 14.9% |
Humanity's Last Exam · with toolsMultidisciplinary reasoning — Humanity's Last Exam — extremely hard expert questions across many subjects. “With tools” means the AI is allowed to search the web or run code while answering. Higher is better. | — | 19% |
MMLUGeneral knowledge — A 57-subject multiple-choice exam — history, law, medicine, maths — that was the standard measure of how much a model knows from 2020 until roughly 2024, when frontier scores crowded into the high 80s and labs moved on to harder tests. The scores here were published years apart under different testing setups, so read them as a historical record rather than a like-for-like ranking. Higher is better. | — | 90% |
MMMUMultimodal — Tests the AI on understanding images and text together across many college subjects. Higher is better. | 76% | — |
| Overview | ||
| Company | OpenAI | OpenAI |
| Release date | Nov 12 2025 | Aug 5 2025 |
| Access | Proprietary | Open Weight |
Other comparisons
Frequently asked questions
GPT-5.1 leads gpt-oss-120b on 3 of the 3 benchmarks they both report (BullshitBench v2, SWE-Bench Verified, GPQA Diamond). Only GPT-5.1 has a verified first-party API price: $1.25 per million input tokens and $10.00 per million output tokens. No pay-as-you-go API rate is tracked for gpt-oss-120b. gpt-oss-120b shipped 99 days before GPT-5.1, so benchmark comparisons should account for the intervening progress.
GPT-5.1 is proprietary, while gpt-oss-120b is open weight.
On BullshitBench v2, GPT-5.1 leads at 25% vs gpt-oss-120b at 11%. On SWE-Bench Verified, GPT-5.1 leads at 76.3% vs gpt-oss-120b at 62.4%. On GPQA Diamond, GPT-5.1 leads at 88.1% vs gpt-oss-120b at 80.1%.
GPT-5.1 was released by OpenAI on Nov 12 2025.
gpt-oss-120b was released by OpenAI on Aug 5 2025.
GPT-5.1 leads on SWE-Bench Verified — GPT-5.1 76.3% vs gpt-oss-120b 62.4%.
GPT-5.1 leads on GPQA Diamond — GPT-5.1 88.1% vs gpt-oss-120b 80.1%.
Only GPT-5.1 has a verified first-party API price: $1.25 per million input tokens and $10.00 per million output tokens. No pay-as-you-go API rate is tracked for gpt-oss-120b. Rates are pay-as-you-go API prices verified on August 18, 2026.
GPT-5.1 is a proprietary model released by OpenAI. gpt-oss-120b is an open weight model released by OpenAI.