Model Comparison
GPT-4.5 vs GPT OSS 120BWhich is better in 2026?
GPT-4.5 shows notably better performance in the majority of benchmarks. GPT OSS 120B is 520.8x cheaper per token.
Verdict: GPT-4.5 vs GPT OSS 120B — which is better?
GPT-4.5 (by OpenAI) and GPT OSS 120B (by OpenAI) are two of the AI models people compare most. Here is how they stack up on benchmarks, price and capabilities, and which one to pick in 2026.
GPT-4.5 outperforms in 2 benchmarks (MMLU, TAU-bench Retail), while GPT OSS 120B is better at 1 benchmark (GPQA). GPT-4.5 shows notably better performance in the majority of benchmarks.
On price, GPT OSS 120B is roughly 520.8x cheaper per token on a blended 3:1 input/output basis, which adds up quickly at production volume.
GPT OSS 120B also accepts a larger context window (131,072 input tokens), making it the stronger choice for long documents and large codebases.
Choose GPT-4.5 if…
- you want the strongest raw capability — it leads on 2 of 3 shared benchmarks
Choose GPT OSS 120B if…
- cost matters — it's about 520.8x cheaper per token
- you process long inputs — it offers a 131,072 token context window
- you want the most recent training data — it shipped Aug 2025
- you need open weights you can self-host or fine-tune
Performance Benchmarks
Comparative analysis across standard metrics
GPT-4.5 outperforms in 2 benchmarks (MMLU, TAU-bench Retail), while GPT OSS 120B is better at 1 benchmark (GPQA).
GPT-4.5 shows notably better performance in the majority of benchmarks.
Arena Performance
Human preference votes
Pricing Analysis
Price comparison per million tokens
For input processing, GPT-4.5 ($75.00/1M tokens) is 833.3x more expensive than GPT OSS 120B ($0.09/1M tokens).
For output processing, GPT-4.5 ($150.00/1M tokens) is 333.3x more expensive than GPT OSS 120B ($0.45/1M tokens).
In conclusion, GPT-4.5 is more expensive than GPT OSS 120B.*
* Using a 3:1 ratio of input to output tokens
Context Window
Maximum input and output token capacity
GPT OSS 120B accepts 131,072 input tokens compared to GPT-4.5's 128,000 tokens. GPT OSS 120B can generate longer responses up to 131,072 tokens, while GPT-4.5 is limited to 4,096 tokens.
Input Capabilities
Supported data types and modalities
GPT-4.5 supports multimodal inputs, whereas GPT OSS 120B does not.
GPT-4.5 can handle both text and other forms of data like images, making it suitable for multimodal applications.
GPT-4.5
GPT OSS 120B
License
Usage and distribution terms
GPT-4.5 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.
Proprietary
Closed source
Apache 2.0
Open weights
Release Timeline
When each model was launched
GPT-4.5 was released on 2025-02-27, while GPT OSS 120B was released on 2025-08-05.
GPT OSS 120B is 5 months newer than GPT-4.5.
Feb 27, 2025
1.3 years ago
Aug 5, 2025
10 months ago
5mo newerKnowledge Cutoff
When training data ends
Neither model specifies a knowledge cutoff date.
Unable to compare the recency of their training data.
Provider Availability
GPT-4.5 is available from OpenAI. GPT OSS 120B is available from DeepInfra, Novita, OpenAI, Fireworks, Groq.
GPT-4.5
GPT OSS 120B
Outputs Comparison
Key Takeaways
GPT-4.5
View detailsOpenAI
GPT OSS 120B
View detailsOpenAI
Detailed Comparison
Interactive Arena
Judge for yourself.
Run your own prompts against GPT-4.5 and GPT OSS 120B side-by-side, then vote on the output you prefer.
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FAQ
Common questions about GPT-4.5 vs GPT OSS 120B.