Noometry

Model comparison

Grok 4.1 Fast vs Llama 3.1-8B

Grok 4.1 Fast is the stronger model overall, scoring 41.4 to 23.0 on the Noometry Index. Llama 3.1-8B costs 4.8× less per token, which makes it the better buy when Grok 4.1 Fast's lead doesn't matter for your workload.

Last verified . 20 shared benchmarks.

Grok 4.1 Fast xAI

41.4

Rank #136 Confirmed

Llama 3.1-8B Meta

23.0

Rank #352 Confirmed

Summary

  • They share 20 benchmarks with published results for both. Grok 4.1 Fast scores higher in 9 categories and Llama 3.1-8B in 0 categories; 9 gaps are clear of the uncertainty.
  • The widest gap is in reasoning, where Grok 4.1 Fast leads 43.4 to 14.9.
  • The biggest single-benchmark swing is Berkeley Function Calling Leaderboard: 69.6% for Grok 4.1 Fast and 25.8% for Llama 3.1-8B.
  • Llama 3.1-8B is cheaper at $0.05 / $0.08 per million input/output tokens, against $0.20 / $0.50 for Grok 4.1 Fast.
  • Llama 3.1-8B has downloadable open weights; the other is API-only.

Side by side

Grok 4.1 FastLlama 3.1-8B
ProviderxAIMeta
Noometry Index41.423.0
Released2025-06-272024-07-23
WeightsProprietaryOpen
Context window128K128K
Max output30K4K
Input $ / M tokens$0.20$0.05
Output $ / M tokens$0.50$0.08
Results tracked3243

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Category by category

Coding Grok 4.1 Fast leads

Grok 4.1 Fast: 34.1 (#245), Llama 3.1-8B: 20.2 (#340)

BenchmarkGrok 4.1 FastLlama 3.1-8B
LMArena Coding14111195
LMArena WebDev1242—
SciCode—13.2%
WeirdML—1.7%
BigCodeBench Instruct—32.8%
BigCodeBench Complete—40.5%
ALE-Bench394.93—
HumanEval+—62.8%
MBPP+—55.6%

Agentic & Tool Use Grok 4.1 Fast leads

Grok 4.1 Fast: 36.3 (#39), Llama 3.1-8B: 22.5 (#131)

BenchmarkGrok 4.1 FastLlama 3.1-8B
Berkeley Function Calling Leaderboard69.6%25.8%
τ²-bench Banking13.1%—
BALROG—15.1%
LMArena Search1171—
Vending-Bench 21,107—

Reasoning Grok 4.1 Fast leads

Grok 4.1 Fast: 43.4 (#49), Llama 3.1-8B: 14.9 (#321)

BenchmarkGrok 4.1 FastLlama 3.1-8B
LMArena Hard Prompts14071175
DTBench87.7%50.9%
SimpleBench56%—
NYT Connections (extended)87.4%—
CritPt—0%
Chess Puzzles—0%
LMCA—5.4%
Epoch Capabilities Index—116.57
ForecastBench61—
PIQA—81.2%

Math Grok 4.1 Fast leads

Grok 4.1 Fast: 31.9 (#221), Llama 3.1-8B: 10.2 (#317)

BenchmarkGrok 4.1 FastLlama 3.1-8B
LMArena Math14081179
MathArena Final-Answer Competitions60.9%—
OTIS Mock AIME 2024-2025—1.7%
ProofBench4%—
Omni-MATH—13.7%
MATH Level 5—22.9%
GSM8K—82.4%

Knowledge Grok 4.1 Fast leads

Grok 4.1 Fast: 33.1 (#207), Llama 3.1-8B: 8.0 (#307)

BenchmarkGrok 4.1 FastLlama 3.1-8B
LMArena Expert13991144
GPQA Diamond—27%
MMLU-Pro—40.6%
Vectara Hallucination Rate17.8%—
GPQA (HELM)—24.7%
BoolQ—82.8%
MMLU—56.1%

Multimodal Not comparable

Grok 4.1 Fast: 37.0 (#76), Llama 3.1-8B: —

BenchmarkGrok 4.1 FastLlama 3.1-8B
LMArena Vision1201—

Multilingual Grok 4.1 Fast leads

Grok 4.1 Fast: 51.0 (#114), Llama 3.1-8B: 34.0 (#249)

BenchmarkGrok 4.1 FastLlama 3.1-8B
LMArena Non-English13911148
LMArena Chinese14411151
LMArena French14151177
LMArena German14041144
LMArena Japanese13491061
LMArena Korean13611053
LMArena Russian13871158
LMArena Spanish14131169

Instruction Following Grok 4.1 Fast leads

Grok 4.1 Fast: 72.7 (#133), Llama 3.1-8B: 58.9 (#258)

BenchmarkGrok 4.1 FastLlama 3.1-8B
LMArena Instruction Following13761159
IFEval—74.3%

Long Context Grok 4.1 Fast leads

Grok 4.1 Fast: 42.4 (#126), Llama 3.1-8B: 35.8 (#238)

BenchmarkGrok 4.1 FastLlama 3.1-8B
LMArena Longer Query13901182

Writing & Preference Grok 4.1 Fast leads

Grok 4.1 Fast: 57.2 (#131), Llama 3.1-8B: 29.7 (#290)

BenchmarkGrok 4.1 FastLlama 3.1-8B
LMArena Text14081187
LMArena Creative Writing13941154
EQ-Bench Creative Writing1327713
LMArena Multi-Turn13891172
WildBench—68.7%

Frequently asked questions

Is Grok 4.1 Fast better than Llama 3.1-8B?

Grok 4.1 Fast is the stronger model overall, scoring 41.4 to 23.0 on the Noometry Index. Llama 3.1-8B costs 4.8× less per token, which makes it the better buy when Grok 4.1 Fast's lead doesn't matter for your workload.

Which is cheaper, Grok 4.1 Fast or Llama 3.1-8B?

Llama 3.1-8B is cheaper. It lists at $0.05 per million input tokens and $0.08 per million output tokens; Grok 4.1 Fast lists at $0.20 and $0.50.

Is Grok 4.1 Fast or Llama 3.1-8B better for coding?

Grok 4.1 Fast scores higher on coding benchmarks: 34.1 versus 20.2 in the Noometry coding category.

Which has the bigger context window?

Both accept 128K tokens.

How many benchmarks do Grok 4.1 Fast and Llama 3.1-8B share?

20 benchmarks have published results for both models. Grok 4.1 Fast has 32 scored results on Noometry and Llama 3.1-8B has 43.

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