Model Comparison
GPT-5.1 Instant vs Llama 3.1 405B InstructWhich is better in 2026?
GPT-5.1 Instant significantly outperforms across most benchmarks. Llama 3.1 405B Instruct is 3.9x cheaper per token.
Verdict: GPT-5.1 Instant vs Llama 3.1 405B Instruct — which is better?
GPT-5.1 Instant (by OpenAI) and Llama 3.1 405B Instruct (by Meta) 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-5.1 Instant outperforms in 1 benchmarks (GPQA), while Llama 3.1 405B Instruct is better at 0 benchmarks. GPT-5.1 Instant significantly outperforms across most benchmarks.
On price, Llama 3.1 405B Instruct is roughly 3.9x cheaper per token on a blended 3:1 input/output basis, which adds up quickly at production volume.
GPT-5.1 Instant also accepts a larger context window (400,000 input tokens), making it the stronger choice for long documents and large codebases.
Choose GPT-5.1 Instant if…
- you want the strongest raw capability — it leads on 1 of 1 shared benchmarks
- you process long inputs — it offers a 400,000 token context window
- you want the most recent training data — it shipped Nov 2025
Choose Llama 3.1 405B Instruct if…
- cost matters — it's about 3.9x cheaper per token
- you need open weights you can self-host or fine-tune
Performance Benchmarks
Comparative analysis across standard metrics
GPT-5.1 Instant outperforms in 1 benchmarks (GPQA), while Llama 3.1 405B Instruct is better at 0 benchmarks.
GPT-5.1 Instant significantly outperforms across most benchmarks.
Arena Performance
Human preference votes
Pricing Analysis
Price comparison per million tokens
For input processing, GPT-5.1 Instant ($1.25/1M tokens) is 1.4x more expensive than Llama 3.1 405B Instruct ($0.89/1M tokens).
For output processing, GPT-5.1 Instant ($10.00/1M tokens) is 11.2x more expensive than Llama 3.1 405B Instruct ($0.89/1M tokens).
In conclusion, GPT-5.1 Instant is more expensive than Llama 3.1 405B Instruct.*
* Using a 3:1 ratio of input to output tokens
Context Window
Maximum input and output token capacity
GPT-5.1 Instant accepts 400,000 input tokens compared to Llama 3.1 405B Instruct's 128,000 tokens. Both models can generate responses up to 128,000 tokens.
Input Capabilities
Supported data types and modalities
GPT-5.1 Instant supports multimodal inputs, whereas Llama 3.1 405B Instruct does not.
GPT-5.1 Instant can handle both text and other forms of data like images, making it suitable for multimodal applications.
GPT-5.1 Instant
Llama 3.1 405B Instruct
License
Usage and distribution terms
GPT-5.1 Instant is licensed under a proprietary license, while Llama 3.1 405B Instruct uses Llama 3.1 Community License.
License differences may affect how you can use these models in commercial or open-source projects.
Proprietary
Closed source
Llama 3.1 Community License
Open weights
Release Timeline
When each model was launched
GPT-5.1 Instant was released on 2025-11-12, while Llama 3.1 405B Instruct was released on 2024-07-23.
GPT-5.1 Instant is 16 months newer than Llama 3.1 405B Instruct.
Nov 12, 2025
8 months ago
1.3yr newerJul 23, 2024
2.0 years ago
Knowledge Cutoff
When training data ends
Neither model specifies a knowledge cutoff date.
Unable to compare the recency of their training data.
Provider Availability
GPT-5.1 Instant is available from OpenAI. Llama 3.1 405B Instruct is available from Lambda, DeepInfra, Fireworks, Bedrock, Together, Hyperbolic, Google, Replicate.
GPT-5.1 Instant
Llama 3.1 405B Instruct
Outputs Comparison
Key Takeaways
Detailed Comparison
Interactive Arena
Judge for yourself.
Run your own prompts against GPT-5.1 Instant and Llama 3.1 405B Instruct side-by-side, then vote on the output you prefer.
| Feature | | |
|---|
FAQ
Common questions about GPT-5.1 Instant vs Llama 3.1 405B Instruct.