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Head-to-head comparison

GPT-5.5 vs gpt-oss-120b

GPT-5.5 (OpenAI) and gpt-oss-120b (OpenAI) compared on the ModelCap Index, API price, context window, provider availability, weight access and every public benchmark board they share. Figures are the same ones shown on the live rankings; nothing here is a hidden score.

Snapshot as of 7 November 2026

As of 7 November 2026, GPT-5.5 holds the stronger ModelCap Index position (#16 vs #164); gpt-oss-120b is 545.5× cheaper per output token ($0.055/1M vs $30.00/1M); GPT-5.5 offers the longer context window (1M vs 131K tokens); and gpt-oss-120b ships open weights.

Which should you choose?

Choose GPT-5.5 if…

  • you want the stronger overall ModelCap Index position — #16 against #164 (80.1 vs 39.6 points).
  • you need the longer context window — 1M tokens against 131K.
  • Arena text is your yardstick — 1482 against 1352.
  • Arena coding is your yardstick — 1519 against 1389.
  • you want the more recently listed model — GPT-5.5 was listed 24 April 2026, gpt-oss-120b 5 August 2025.

Choose gpt-oss-120b if…

  • API cost matters — $0.055/1M output tokens against $30.00/1M, about 545.5× cheaper.
  • your workload is prompt-heavy — input tokens cost $0.015/1M against $5.00/1M.
  • you want to self-host: gpt-oss-120b ships open weights while GPT-5.5 is no linked weights.
  • you want provider choice — 22 listed API providers against 3.

GPT-5.5 vs gpt-oss-120b: specs, pricing and context

Specification comparison of GPT-5.5 and gpt-oss-120b
FieldGPT-5.5OpenAIgpt-oss-120bOpenAI
ModelCap Index position#16#164
Index score80.139.6
EvidenceMeasuredMeasured
Input price / 1M tokens$5.00$0.015
Output price / 1M tokens$30.00$0.055
Context window1M tokens131K tokens
Declared route output cap128K66K
API providers listed322
Weight accessNo linked weightsOpen weights
Input modalitiesFile, Image, TextText
First listed24 April 20265 August 2025
PublisherOpenAIOpenAI

Evidence: 4 public benchmark observations across 4 boards · 2 public benchmark observations across 2 boards. Prices are the lowest listed API offer per million tokens observed on the OpenRouter catalogue.

Benchmark scores: GPT-5.5 vs gpt-oss-120b

Public benchmark boards where GPT-5.5 or gpt-oss-120b has a published result
BoardGPT-5.5gpt-oss-120bLeads
Arena textArena (LMArena)14821478–1485High13521347–1356Not reportedGPT-5.5
Arena codingArena (LMArena)15191513–1525High13891381–1397GPT-5.5
ARC-AGI-2ARC Prize Foundation85.0%X-High—Only one result
ARC-AGI-3ARC Prize Foundation0.4%High—Only one result
SWE-benchSWE-bench (Princeton / SWE-agent team)—26.0%Only one result
Terminal-Bench 2.1 Terminus 2Terminal-Bench78.0X-High—Only one result
WildClawBench OpenClawWildClawBench58.2—Only one result

Scores are the sources' own published figures for each model's best evaluated configuration; ModelCap never re-runs a benchmark.

Want a different pairing? Open the interactive comparison tool to swap either model for any current ranked language model.

GPT-5.5 vs gpt-oss-120b: common questions

Is GPT-5.5 better than gpt-oss-120b?

GPT-5.5 ranks higher on the ModelCap Index as of 7 November 2026: #16 against #164. That is a capability ranking built from public benchmark evidence with published uncertainty; whether it is "better" for you also depends on price, context and where you can run it. Their published uncertainty intervals do not overlap, but the aggregate Index does not predict performance on every task; compare the relevant benchmark configurations before choosing.

Is GPT-5.5 cheaper than gpt-oss-120b?

gpt-oss-120b is cheaper on output tokens: $0.055/1M against $30.00/1M. Input tokens are $5.00/1M for GPT-5.5 and $0.015/1M for gpt-oss-120b. Prices are the lowest listed API offer ModelCap observed, in USD per million tokens. For 1,000 requests with 2,000 input and 500 output tokens each (2M input + 0.5M output), the listed-rate estimate is $25.00 for GPT-5.5 versus $0.06 for gpt-oss-120b. gpt-oss-120b costs 99.8% less in this scenario. This excludes caching, batch discounts, prompt-length tiers, tool charges and retries; verify the selected endpoint before budgeting.

Which has the bigger context window, GPT-5.5 or gpt-oss-120b?

GPT-5.5 has the larger context window: 1M tokens against 131K. OpenRouter catalogue or provider-endpoint declaration. Limits can vary by provider and prompt length; a model-wide maximum has not been independently verified.

Which is better for coding, GPT-5.5 or gpt-oss-120b?

Arena coding: GPT-5.5 1519, gpt-oss-120b 1389 — GPT-5.5 leads.

Are GPT-5.5 and gpt-oss-120b open-weight models?

GPT-5.5: No linked weights. gpt-oss-120b: Open weights. Open weights mean the checkpoint can be downloaded and self-hosted under its licence. A missing weight link does not identify every API or chat product that offers a model.

Where can I run GPT-5.5 and gpt-oss-120b?

ModelCap currently lists 3 API providers for GPT-5.5 and 22 for gpt-oss-120b, from the OpenRouter catalogue snapshot the site serves; each model page lists the providers and their prices.

How current is this GPT-5.5 vs gpt-oss-120b comparison?

Every figure and ModelCap Index position comes from the same published snapshot dated 7 November 2026. Publication and page updates happen separately; use the snapshot date shown on the page.

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