Noometry

Model comparison

GPT-6 Luna vs Grok 4.1 Fast

GPT-6 Luna is the stronger model overall, scoring 53.3 to 41.4 on the Noometry Index.

Last verified . 23 shared benchmarks.

GPT-6 Luna OpenAI

53.3

Rank #36 Confirmed

Grok 4.1 Fast xAI

41.4

Rank #136 Confirmed

Summary

  • They share 23 benchmarks with published results for both. GPT-6 Luna scores higher in 8 categories and Grok 4.1 Fast in 2 categories; 8 gaps are clear of the uncertainty.
  • The widest gap is in math, where GPT-6 Luna leads 76.1 to 31.9.
  • The biggest single-benchmark swing is ProofBench: 64% for GPT-6 Luna and 4% for Grok 4.1 Fast.
  • GPT-6 Luna is cheaper at $0.10 / $0.50 per million input/output tokens, against $0.20 / $0.50 for Grok 4.1 Fast.
  • GPT-6 Luna accepts more context: 1.05M tokens versus 128K.

Side by side

GPT-6 LunaGrok 4.1 Fast
ProviderOpenAIxAI
Noometry Index53.341.4
Released2026-09-222025-06-27
WeightsProprietaryProprietary
Context window1.05M128K
Max output128K30K
Input $ / M tokens$0.10$0.20
Output $ / M tokens$0.50$0.50
Results tracked4232

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Category by category

Coding GPT-6 Luna leads

GPT-6 Luna: 55.5 (#25), Grok 4.1 Fast: 34.1 (#245)

BenchmarkGPT-6 LunaGrok 4.1 Fast
LMArena WebDev15811242
LMArena Coding14391411
ALE-Bench1,577394.93
DeepSWE66.6%—
FrontierCode42.4%—
SciCode54.6%—

Agentic & Tool Use Grok 4.1 Fast leads

GPT-6 Luna: 33.3 (#54), Grok 4.1 Fast: 36.3 (#39)

BenchmarkGPT-6 LunaGrok 4.1 Fast
APEX-Agents44.3%—
Berkeley Function Calling Leaderboard—69.6%
τ²-bench Banking—13.1%
GDP.pdf23%—
LMArena Search—1171
Vending-Bench 2—1,107

Reasoning GPT-6 Luna leads

GPT-6 Luna: 48.2 (#41), Grok 4.1 Fast: 43.4 (#49)

BenchmarkGPT-6 LunaGrok 4.1 Fast
NYT Connections (extended)68.7%87.4%
LMArena Hard Prompts14111407
DTBench90.1%87.7%
ARC-AGI-259.3%—
SimpleBench—56%
ARC-AGI-186.7%—
CritPt19.4%—
Chess Puzzles31%—
Mystery Game Puzzles7%—
LMCA44.5%—
Epoch Capabilities Index156.28—
ForecastBench—61

Math GPT-6 Luna leads

GPT-6 Luna: 76.1 (#15), Grok 4.1 Fast: 31.9 (#221)

BenchmarkGPT-6 LunaGrok 4.1 Fast
ProofBench64%4%
LMArena Math14161408
FrontierMath (Tiers 1-3)78.9%—
FrontierMath Tier 456.1%—
MathArena Final-Answer Competitions—60.9%
OTIS Mock AIME 2024-202598.9%—

Knowledge GPT-6 Luna leads

GPT-6 Luna: 57.0 (#41), Grok 4.1 Fast: 33.1 (#207)

BenchmarkGPT-6 LunaGrok 4.1 Fast
LMArena Expert14441399
GPQA Diamond90.5%—
SimpleQA Verified41.4%—
Vectara Hallucination Rate—17.8%

Multimodal GPT-6 Luna leads

GPT-6 Luna: 42.4 (#30), Grok 4.1 Fast: 37.0 (#76)

BenchmarkGPT-6 LunaGrok 4.1 Fast
LMArena Vision12171201
Blueprint-Bench 231.2%—
Furniture Assembly44.2%—

Multilingual Too close to call

GPT-6 Luna: 50.5 (#117), Grok 4.1 Fast: 51.0 (#114)

BenchmarkGPT-6 LunaGrok 4.1 Fast
LMArena Non-English13861391
LMArena Chinese14331441
LMArena French14201415
LMArena German13691404
LMArena Japanese13691349
LMArena Korean13601361
LMArena Russian13941387
LMArena Spanish13931413

Instruction Following GPT-6 Luna leads

GPT-6 Luna: 74.3 (#99), Grok 4.1 Fast: 72.7 (#133)

BenchmarkGPT-6 LunaGrok 4.1 Fast
LMArena Instruction Following14091376

Long Context Too close to call

GPT-6 Luna: 43.0 (#111), Grok 4.1 Fast: 42.4 (#126)

BenchmarkGPT-6 LunaGrok 4.1 Fast
LMArena Longer Query14091390

Writing & Preference GPT-6 Luna leads

GPT-6 Luna: 58.3 (#119), Grok 4.1 Fast: 57.2 (#131)

BenchmarkGPT-6 LunaGrok 4.1 Fast
LMArena Text13911408
LMArena Creative Writing13631394
LMArena Multi-Turn13961389
EQ-Bench Creative Writing—1327

Frequently asked questions

Is GPT-6 Luna better than Grok 4.1 Fast?

GPT-6 Luna is the stronger model overall, scoring 53.3 to 41.4 on the Noometry Index.

Which is cheaper, GPT-6 Luna or Grok 4.1 Fast?

GPT-6 Luna is cheaper. It lists at $0.10 per million input tokens and $0.50 per million output tokens; Grok 4.1 Fast lists at $0.20 and $0.50.

Is GPT-6 Luna or Grok 4.1 Fast better for coding?

GPT-6 Luna scores higher on coding benchmarks: 55.5 versus 34.1 in the Noometry coding category.

Which has the bigger context window?

GPT-6 Luna does, with 1.05M tokens against 128K.

How many benchmarks do GPT-6 Luna and Grok 4.1 Fast share?

23 benchmarks have published results for both models. GPT-6 Luna has 42 scored results on Noometry and Grok 4.1 Fast has 32.

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