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Claude Opus 5.5 vs GPT OSS 120B

Claude Opus 5.5 leads the LLM Stats Score 59.7 to 28.7. GPT OSS 120B is 113.9x cheaper per token.

Anthropic · OpenAI · Updated for 2026

Which is better?

Claude Opus 5.5 leads the overall LLM Stats Score 59.7 to 28.7, ranking #1 overall.

In the 1 individual benchmarks reported for both models, Claude Opus 5.5 wins 1; this is a narrower head-to-head signal than the composite indexes.

On price, GPT OSS 120B is roughly 113.9x cheaper per token on a blended 3:1 input/output basis, which adds up quickly at production volume.

Claude Opus 5.5 also accepts a larger context window (1,000,000 input tokens), making it the stronger choice for long documents and large codebases.

Based on current LLM Stats indexes, shared benchmarks, pricing, and model metadata for 2026.

Choose Claude Opus 5.5

  • overall performance matters — it scores 59.7 and ranks #1 on LLM Stats
  • your work emphasizes reasoning — it leads those capability indexes
  • you value its reported benchmark strengths — it wins 1 of 1 exact shared results
  • you process long inputs — it offers a 1,000,000 token context window
  • you want the most recent training data — it shipped Sep 2026

Choose GPT OSS 120B

  • cost matters — it's about 113.9x cheaper per token
  • you need open weights you can self-host or fine-tune

At a glance

The differences that matter most.

Claude Opus 5.5
Anthropic
GPT OSS 120B
OpenAI
Core performance indexes
LLM Stats Score
59.7
#1
28.7
#138
Reasoning
57.8
#1
23.0
#172
Cost, coverage & limits
Benchmark wins
1 of 1
0 of 1
Input price
$4.00 / M
$0.04 / M
Output price
$20.00 / M
$0.17 / M
Context window
1,000,000
131,072

Capability indexes

Additional strengths measured across groups of related public benchmarks

1 shared
Index
Claude Opus 5.5
GPT OSS 120B
Math
42.5#5
23.3#132
Conservative TrueSkill rating · higher is betterHow scores work

Individual benchmarks

31 reported for Claude Opus 5.5 · 7 for GPT OSS 120B

1 shared

Claude Opus 5.5 outperforms in 1 benchmarks (HealthBench), while GPT OSS 120B is better at 0 benchmarks.

Claude Opus 5.5 significantly outperforms across most benchmarks.

Tue Sep 22 2026 • llm-stats.com

Human preference

Blind head-to-head votes and playground preference scores

Pricing Analysis

Price comparison per million tokens

GPT OSS 120B costs less

For input processing, Claude Opus 5.5 ($4.00/1M tokens) is 108.1x more expensive than GPT OSS 120B ($0.04/1M tokens).

For output processing, Claude Opus 5.5 ($20.00/1M tokens) is 117.6x more expensive than GPT OSS 120B ($0.17/1M tokens).

In conclusion, Claude Opus 5.5 is more expensive than GPT OSS 120B.*

* Using a 3:1 ratio of input to output tokens

Lowest available price from all providers
Tue Sep 22 2026 • llm-stats.com
Anthropic
Claude Opus 5.5
Input tokens$4.00
Output tokens$20.00
Best providerAnthropic
OpenAI
GPT OSS 120B
Input tokens$0.04
Output tokens$0.17
Best providerDeepinfra
Notice missing or incorrect data?Start an Issue→

Context Window

Maximum input and output token capacity

Claude Opus 5.5 accepts 1,000,000 input tokens compared to GPT OSS 120B's 131,072 tokens. GPT OSS 120B can generate longer responses up to 131,072 tokens, while Claude Opus 5.5 is limited to 128,000 tokens.

Anthropic
Claude Opus 5.5
Input1,000,000 tokens
Output128,000 tokens
OpenAI
GPT OSS 120B
Input131,072 tokens
Output131,072 tokens
Tue Sep 22 2026 • llm-stats.com

Input capabilities

Documented input modalities across available providers

Claude Opus 5.5 supports multimodal inputs, whereas GPT OSS 120B does not.

Claude Opus 5.5 can handle both text and other forms of data like images, making it suitable for multimodal applications.

Claude Opus 5.5

Text
Images
Audio
Video

GPT OSS 120B

Text
Images
Audio
Video

License

Usage and distribution terms

Claude Opus 5.5 is licensed under a proprietary license, while GPT OSS 120B uses Apache 2.0.

License differences may affect how you can use these models in commercial or open-source projects.

Claude Opus 5.5

Proprietary

Closed source

GPT OSS 120B

Apache 2.0

Open weights

Release Timeline

When each model was launched

Claude Opus 5.5 was released on 2026-09-22, while GPT OSS 120B was released on 2025-08-05.

Claude Opus 5.5 is 14 months newer than GPT OSS 120B.

Claude Opus 5.5

Sep 22, 2026

0 days ago

1.1yr newer
GPT OSS 120B

Aug 5, 2025

1.1 years ago

Knowledge Cutoff

When training data ends

Claude Opus 5.5 has a documented knowledge cutoff of 2026-06-01, while GPT OSS 120B's cutoff date is not specified.

We can confirm Claude Opus 5.5's training data extends to 2026-06-01, but cannot make a direct comparison without GPT OSS 120B's cutoff date.

Claude Opus 5.5

Jun 2026

GPT OSS 120B

—

Provider Availability

Claude Opus 5.5 is available from Anthropic. GPT OSS 120B is available from DeepInfra, Novita, OpenAI, Fireworks, Groq.

Claude Opus 5.5

anthropic logo
Anthropic
Input Price:Input: $4.00/1MOutput Price:Output: $20.00/1M

GPT OSS 120B

deepinfra logo
Deepinfra
Input Price:Input: $0.04/1MOutput Price:Output: $0.17/1M
novita logo
Novita
Input Price:Input: $0.10/1MOutput Price:Output: $0.50/1M
openai logo
OpenAI
Input Price:Input: $0.10/1MOutput Price:Output: $0.50/1M
fireworks logo
Fireworks
Input Price:Input: $0.15/1MOutput Price:Output: $0.60/1M
groq logo
Groq
Input Price:Input: $0.15/1MOutput Price:Output: $0.60/1M
* Prices shown are per million tokens

Outputs Comparison

Notice missing or incorrect data?Start an Issue discussion→

Judge for yourself.

Run your own prompts against Claude Opus 5.5 and GPT OSS 120B side-by-side, then vote on the output you prefer.

Claude Opus 5.5
✓ Preferred
GPT OSS 120B
Open in Playground

FAQ

Common questions about Claude Opus 5.5 vs GPT OSS 120B.

Which is better, Claude Opus 5.5 or GPT OSS 120B?

Claude Opus 5.5 leads the LLM Stats Score 59.7 to 28.7. Claude Opus 5.5 is made by Anthropic and GPT OSS 120B is made by OpenAI. The best choice depends on your use case — compare their capability indexes, individual benchmarks, pricing, and limits above.

How does Claude Opus 5.5 compare to GPT OSS 120B in benchmarks?

Claude Opus 5.5 scores BenchCAD (with Python tool): 96.2%, Global-MMLU: 94.3%, SWE-bench Multilingual: 93.9%, MILU: 93.1%, ArXivMath: 91.2%. GPT OSS 120B scores MMLU: 90.0%, CodeForces: 82.1%, GPQA: 80.1%, TAU-bench Retail: 67.8%, HealthBench: 57.6%.

Is Claude Opus 5.5 cheaper than GPT OSS 120B?

GPT OSS 120B is 108.1x cheaper for input tokens. Claude Opus 5.5 costs $4.00/M input and $20.00/M output via anthropic. GPT OSS 120B costs $0.04/M input and $0.17/M output via deepinfra.

What are the context window sizes for Claude Opus 5.5 and GPT OSS 120B?

Claude Opus 5.5 supports 1.0M tokens and GPT OSS 120B supports 131K tokens. A larger context window lets you process longer documents, conversations, or codebases in a single request.

What are the main differences between Claude Opus 5.5 and GPT OSS 120B?

Key differences include LLM Stats Score (59.7 vs 28.7), context window (1.0M vs 131K), input pricing ($4.00 vs $0.04/M), multimodal support (yes vs no), licensing (Proprietary vs Apache 2.0). See the full comparison above for benchmark-by-benchmark results.

Who makes Claude Opus 5.5 and GPT OSS 120B?

Claude Opus 5.5 is developed by Anthropic and GPT OSS 120B is developed by OpenAI.

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