Noometry

Model comparison

Grok 4 Fast vs Llama 3.1-405B

Grok 4 Fast is the stronger model overall, scoring 39.4 to 30.7 on the Noometry Index.

Last verified . 23 shared benchmarks.

Grok 4 Fast xAI

39.4

Rank #167 Confirmed

Llama 3.1-405B Meta

30.7

Rank #288 Confirmed

Summary

  • They share 23 benchmarks with published results for both. Grok 4 Fast scores higher in 8 categories and Llama 3.1-405B in 1 category; 8 gaps are clear of the uncertainty.
  • The widest gap is in long context, where Grok 4 Fast leads 63.2 to 38.4.
  • The biggest single-benchmark swing is Cybench: 30% for Grok 4 Fast and 7.5% for Llama 3.1-405B.
  • Llama 3.1-405B has downloadable open weights; the other is API-only.

Side by side

Grok 4 FastLlama 3.1-405B
ProviderxAIMeta
Noometry Index39.430.7
Released2025-09-192024-07-23
WeightsProprietaryOpen
Context window——
Max output——
Input $ / M tokens——
Output $ / M tokens——
Results tracked3042

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Category by category

Coding Too close to call

Grok 4 Fast: 32.5 (#271), Llama 3.1-405B: 33.1 (#262)

BenchmarkGrok 4 FastLlama 3.1-405B
WeirdML42.9%21.4%
LMArena Coding14291291
LMArena WebDev1159—

Agentic & Tool Use Grok 4 Fast leads

Grok 4 Fast: 29.5 (#86), Llama 3.1-405B: 21.0 (#140)

BenchmarkGrok 4 FastLlama 3.1-405B
Cybench30%7.5%
TheAgentCompany—7.4%
τ²-bench Banking15.7%—
LMArena Search1171—

Reasoning Grok 4 Fast leads

Grok 4 Fast: 22.2 (#201), Llama 3.1-405B: 16.8 (#300)

BenchmarkGrok 4 FastLlama 3.1-405B
Kagi LLM Benchmark66.1%45%
LMArena Hard Prompts14121269
DTBench82.7%61.4%
Epoch Capabilities Index144.2128.75
ForecastBench60.559.9
ARC-AGI-25.3%—
SimpleBench—23%
ARC-AGI-148.5%—
BIG-Bench Hard—82.9%
HellaSwag—89.2%
PIQA—85.9%
WinoGrande—89.2%

Math Grok 4 Fast leads

Grok 4 Fast: 38.9 (#123), Llama 3.1-405B: 18.4 (#290)

BenchmarkGrok 4 FastLlama 3.1-405B
LMArena Math14191281
OTIS Mock AIME 2024-2025—9.7%
Omni-MATH—24.9%
MATH Level 5—49.8%

Knowledge Grok 4 Fast leads

Grok 4 Fast: 32.0 (#214), Llama 3.1-405B: 30.4 (#227)

BenchmarkGrok 4 FastLlama 3.1-405B
LMArena Expert14111243
GPQA Diamond—50.9%
MMLU-Pro—72.3%
Confabulations—17.6%
Vectara Hallucination Rate19.7%—
GPQA (HELM)—52.2%
ARC (AI2) Challenge—95.3%
MMLU—84.5%
TriviaQA—82.7%

Multilingual Grok 4 Fast leads

Grok 4 Fast: 51.3 (#111), Llama 3.1-405B: 40.7 (#214)

BenchmarkGrok 4 FastLlama 3.1-405B
LMArena Non-English13961248
LMArena Chinese14571242
LMArena French14311279
LMArena German13831252
LMArena Japanese13521208
LMArena Korean13571184
LMArena Russian13891265
LMArena Spanish14151260

Instruction Following Grok 4 Fast leads

Grok 4 Fast: 73.2 (#121), Llama 3.1-405B: 65.9 (#214)

BenchmarkGrok 4 FastLlama 3.1-405B
LMArena Instruction Following13871259
IFEval—81.1%

Long Context Grok 4 Fast leads

Grok 4 Fast: 63.2 (#3), Llama 3.1-405B: 38.4 (#197)

BenchmarkGrok 4 FastLlama 3.1-405B
LMArena Longer Query14151266
Fiction.LiveBench94.4%—

Writing & Preference Grok 4 Fast leads

Grok 4 Fast: 60.0 (#102), Llama 3.1-405B: 38.9 (#251)

BenchmarkGrok 4 FastLlama 3.1-405B
LMArena Text14071284
LMArena Creative Writing13871262
LMArena Multi-Turn14141297
EQ-Bench Creative Writing—870
WildBench—78.3%

Frequently asked questions

Is Grok 4 Fast better than Llama 3.1-405B?

Grok 4 Fast is the stronger model overall, scoring 39.4 to 30.7 on the Noometry Index.

Is Grok 4 Fast or Llama 3.1-405B better for coding?

They score almost the same on coding (32.5 vs 33.1); test both on your own repository before choosing.

How many benchmarks do Grok 4 Fast and Llama 3.1-405B share?

23 benchmarks have published results for both models. Grok 4 Fast has 30 scored results on Noometry and Llama 3.1-405B has 42.

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