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Grok 4.5 vs Nemotron 3 Ultra (550B A55B)

Grok 4.5 leads the LLM Stats Score 45.5 to 36.3.

xAI · NVIDIA · Updated for 2026

Which is better?

Grok 4.5 leads the overall LLM Stats Score 45.5 to 36.3, ranking #27 overall.

In the 3 individual benchmarks reported for both models, Grok 4.5 wins 2; this is a narrower head-to-head signal than the composite indexes.

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

Choose Grok 4.5

  • overall performance matters — it scores 45.5 and ranks #27 on LLM Stats
  • your work emphasizes reasoning and coding — it leads those capability indexes
  • you value its reported benchmark strengths — it wins 2 of 3 exact shared results
  • you want the most recent training data — it shipped Jul 2026

Choose Nemotron 3 Ultra (550B A55B)

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

At a glance

The differences that matter most.

Grok 4.5
xAI
Nemotron 3 Ultra (550B A55B)
NVIDIA
Core performance indexes
LLM Stats Score
45.5
#27
36.3
#74
Reasoning
43.8
#35
35.4
#76
Coding
35.3
#27
21.3
#84
Agents
30.6
#30
11.7
#98
Cost, coverage & limits
Benchmark wins
2 of 3
1 of 3
Input price
$2.00 / M
— / M
Output price
$6.00 / M
— / M
Context window
500,000
—

Capability indexes

Additional strengths measured across groups of related public benchmarks

1 shared
Index
Grok 4.5
Nemotron 3 Ultra (550B A55B)
Tool use
22.0#45
3.7#154
Conservative TrueSkill rating · higher is betterHow scores work

Individual benchmarks

15 reported for Grok 4.5 · 26 for Nemotron 3 Ultra (550B A55B)

3 shared

Grok 4.5 outperforms in 2 benchmarks (GPQA, Terminal-Bench 2.1), while Nemotron 3 Ultra (550B A55B) is better at 1 benchmark (OmniScience).

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

Sun Sep 06 2026 • llm-stats.com

Human preference

Blind head-to-head votes and playground preference scores

Context Window

Maximum input and output token capacity

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

xAI
Grok 4.5
Input500,000 tokens
Output- tokens
NVIDIA
Nemotron 3 Ultra (550B A55B)
Input- tokens
Output- tokens
Sun Sep 06 2026 • llm-stats.com

Input capabilities

Documented input modalities across available providers

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.

Grok 4.5

Text
Images
Audio
Video

Nemotron 3 Ultra (550B A55B)

Text
Images
Audio
Video

License

Usage and distribution terms

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

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

Grok 4.5

Proprietary

Closed source

Nemotron 3 Ultra (550B A55B)

OpenMDW License v1.1

Open weights

Release Timeline

When each model was launched

Grok 4.5 was released on 2026-07-16, while Nemotron 3 Ultra (550B A55B) was released on 2026-06-04.

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

Grok 4.5

Jul 16, 2026

1 months ago

1mo newer
Nemotron 3 Ultra (550B A55B)

Jun 4, 2026

3 months ago

Knowledge Cutoff

When training data ends

Grok 4.5 has a knowledge cutoff of 2026-02-01, while Nemotron 3 Ultra (550B A55B) has a cutoff of 2025-09-30.

Grok 4.5 has more recent training data (up to 2026-02-01), making it potentially better informed about events through that date compared to Nemotron 3 Ultra (550B A55B) (2025-09-30).

Grok 4.5

Feb 2026

5 mo newer
Nemotron 3 Ultra (550B A55B)

Sep 2025

Outputs Comparison

Notice missing or incorrect data?Start an Issue discussion→

Judge for yourself.

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

Grok 4.5
✓ Preferred
Nemotron 3 Ultra (550B A55B)
Open in Playground

FAQ

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

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

Grok 4.5 leads the LLM Stats Score 45.5 to 36.3. Grok 4.5 is made by xAI and Nemotron 3 Ultra (550B A55B) is made by NVIDIA. The best choice depends on your use case — compare their capability indexes, individual benchmarks, pricing, and limits above.

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

Grok 4.5 scores GPQA: 93.0%, Terminal-Bench 2.1: 83.3%, SWE-Bench Pro: 64.7%, AA-Omniscience Index: 63.0%, DeepSWE 1.0: 62.0%. Nemotron 3 Ultra (550B A55B) scores RULER: 94.7%, IMO-AnswerBench: 92.3%, PinchBench: 90.0%, LiveCodeBench v6: 89.0%, GPQA: 87.0%.

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

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

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

Key differences include LLM Stats Score (45.5 vs 36.3), multimodal support (yes vs no), licensing (Proprietary vs OpenMDW License v1.1). See the full comparison above for benchmark-by-benchmark results.

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

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

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