Model Comparison

Nemotron 3 Ultra (550B A55B) vs Grok 4.5Which is better in 2026?

Grok 4.5 shows notably better performance in the majority of benchmarks.

Verdict: Nemotron 3 Ultra (550B A55B) vs Grok 4.5 — which is better?

Nemotron 3 Ultra (550B A55B) (by NVIDIA) and Grok 4.5 (by xAI) 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.

Nemotron 3 Ultra (550B A55B) outperforms in 1 benchmarks (OmniScience), while Grok 4.5 is better at 3 benchmarks (GDPval-AA, GPQA, Terminal-Bench 2.1). Grok 4.5 shows notably better performance in the majority of benchmarks.

Choose Nemotron 3 Ultra (550B A55B) if…

  • you need open weights you can self-host or fine-tune

Choose Grok 4.5 if…

  • you want the strongest raw capability — it leads on 3 of 4 shared benchmarks
  • you want the most recent training data — it shipped Jul 2026

Performance Benchmarks

Comparative analysis across standard metrics

4 benchmarks

Nemotron 3 Ultra (550B A55B) outperforms in 1 benchmarks (OmniScience), while Grok 4.5 is better at 3 benchmarks (GDPval-AA, GPQA, Terminal-Bench 2.1).

Grok 4.5 shows notably better performance in the majority of benchmarks.

Fri Jul 17 2026 • llm-stats.com

Arena Performance

Human preference votes

Context Window

Maximum input and output token capacity

Only Grok 4.5 specifies input context (500,000 tokens).

NVIDIA
Nemotron 3 Ultra (550B A55B)
Input- tokens
Output- tokens
xAI
Grok 4.5
Input500,000 tokens
Output- tokens
Fri Jul 17 2026 • llm-stats.com

Input Capabilities

Supported data types and modalities

Grok 4.5 supports multimodal inputs, whereas Nemotron 3 Ultra (550B A55B) does not.

Grok 4.5 can handle both text and other forms of data like images, making it suitable for multimodal applications.

Nemotron 3 Ultra (550B A55B)

Text
Images
Audio
Video

Grok 4.5

Text
Images
Audio
Video

License

Usage and distribution terms

Nemotron 3 Ultra (550B A55B) is licensed under OpenMDW License v1.1, while Grok 4.5 uses a proprietary license.

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

Nemotron 3 Ultra (550B A55B)

OpenMDW License v1.1

Open weights

Grok 4.5

Proprietary

Closed source

Release Timeline

When each model was launched

Nemotron 3 Ultra (550B A55B) was released on 2026-06-04, while Grok 4.5 was released on 2026-07-08.

Grok 4.5 is 1 month newer than Nemotron 3 Ultra (550B A55B).

Nemotron 3 Ultra (550B A55B)

Jun 4, 2026

1 months ago

Grok 4.5

Jul 8, 2026

1 weeks ago

1mo newer

Knowledge Cutoff

When training data ends

Nemotron 3 Ultra (550B A55B) has a documented knowledge cutoff of 2025-09-30, while Grok 4.5's cutoff date is not specified.

We can confirm Nemotron 3 Ultra (550B A55B)'s training data extends to 2025-09-30, but cannot make a direct comparison without Grok 4.5's cutoff date.

Nemotron 3 Ultra (550B A55B)

Sep 2025

Grok 4.5

—

Outputs Comparison

Notice missing or incorrect data?Start an Issue discussion→

Key Takeaways

NVIDIA
Has open weights
Higher OmniScience score (78.7% vs 52.0%)
xAI
Larger context window (500,000 tokens)
Supports multimodal inputs
Higher GDPval-AA score (51.4% vs 39.4%)
Higher GPQA score (93.0% vs 87.0%)
Higher Terminal-Bench 2.1 score (83.3% vs 56.4%)

Detailed Comparison

Interactive Arena

Judge for yourself.

Run your own prompts against Nemotron 3 Ultra (550B A55B) and Grok 4.5 side-by-side, then vote on the output you prefer.

Nemotron 3 Ultra (550B A55B)
✓ Preferred
Grok 4.5
Open in Playground
AI Model Comparison Table
Feature
NVIDIA
Nemotron 3 Ultra (550B A55B)
xAI
Grok 4.5

FAQ

Common questions about Nemotron 3 Ultra (550B A55B) vs Grok 4.5.

Which is better, Nemotron 3 Ultra (550B A55B) or Grok 4.5?

Grok 4.5 shows notably better performance in the majority of benchmarks. Nemotron 3 Ultra (550B A55B) is made by NVIDIA and Grok 4.5 is made by xAI. The best choice depends on your use case — compare their benchmark scores, pricing, and capabilities above.

How does Nemotron 3 Ultra (550B A55B) compare to Grok 4.5 in benchmarks?

Nemotron 3 Ultra (550B A55B) scores RULER: 94.7%, IMO-AnswerBench: 92.3%, PinchBench: 90.0%, LiveCodeBench v6: 89.0%, GPQA: 87.0%. Grok 4.5 scores GPQA: 93.0%, Terminal-Bench 2.1: 83.3%, Artificial Analysis Coding Agent Index v1.1: 76.0%, SWE-Bench Pro: 64.7%, AA-Omniscience Index: 63.0%.

What are the context window sizes for Nemotron 3 Ultra (550B A55B) and Grok 4.5?

Nemotron 3 Ultra (550B A55B) supports an unknown number of tokens and Grok 4.5 supports 500K tokens. A larger context window lets you process longer documents, conversations, or codebases in a single request.

What are the main differences between Nemotron 3 Ultra (550B A55B) and Grok 4.5?

Key differences include multimodal support (no vs yes), licensing (OpenMDW License v1.1 vs Proprietary). See the full comparison above for benchmark-by-benchmark results.

Who makes Nemotron 3 Ultra (550B A55B) and Grok 4.5?

Nemotron 3 Ultra (550B A55B) is developed by NVIDIA and Grok 4.5 is developed by xAI.

Related comparisons