Noometry

Model comparison

Grok 4.5 vs Grok 4 Fast

Grok 4.5 is the stronger model overall, scoring 55.0 to 39.4 on the Noometry Index.

Last verified . 26 shared benchmarks.

Grok 4.5 xAI

55.0

Rank #25 Confirmed

Grok 4 Fast xAI

39.4

Rank #167 Confirmed

Summary

  • They share 26 benchmarks with published results for both. Grok 4.5 scores higher in 8 categories and Grok 4 Fast in 1 category; 9 gaps are clear of the uncertainty.
  • The widest gap is in reasoning, where Grok 4.5 leads 56.1 to 22.2.
  • The biggest single-benchmark swing is ARC-AGI-2: 52.6% for Grok 4.5 and 5.3% for Grok 4 Fast.

Side by side

Grok 4.5Grok 4 Fast
ProviderxAIxAI
Noometry Index55.039.4
Released2026-07-082025-09-19
WeightsProprietaryProprietary
Context window500K—
Max output500K—
Input $ / M tokens$2—
Output $ / M tokens$6—
Results tracked5230

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Category by category

Coding Grok 4.5 leads

Grok 4.5: 52.2 (#35), Grok 4 Fast: 32.5 (#271)

BenchmarkGrok 4.5Grok 4 Fast
LMArena WebDev15531159
WeirdML46.4%42.9%
LMArena Coding14741429
DeepSWE53.8%—
FrontierCode42.4%—
SciCode54.1%—
ALE-Bench1,309—

Agentic & Tool Use Grok 4.5 leads

Grok 4.5: 44.4 (#17), Grok 4 Fast: 29.5 (#86)

BenchmarkGrok 4.5Grok 4 Fast
τ²-bench Banking47.9%15.7%
LMArena Search12131171
APEX-Agents56.2%—
Cybench—30%
PostTrainBench23.4%—
GBAEval65.4%—
GDP.pdf14%—
Vending-Bench 23,887—

Reasoning Grok 4.5 leads

Grok 4.5: 56.1 (#25), Grok 4 Fast: 22.2 (#201)

BenchmarkGrok 4.5Grok 4 Fast
ARC-AGI-252.6%5.3%
Kagi LLM Benchmark83.5%66.1%
ARC-AGI-187.2%48.5%
LMArena Hard Prompts14621412
DTBench96.5%82.7%
Epoch Capabilities Index153.92144.2
SimpleBench70%—
NYT Connections (extended)79.9%—
CritPt15.4%—
Chess Puzzles36%—
LMCA45.2%—
Surface Evolver Bench74.4%—
ForecastBench—60.5

Math Grok 4.5 leads

Grok 4.5: 60.9 (#35), Grok 4 Fast: 38.9 (#123)

BenchmarkGrok 4.5Grok 4 Fast
LMArena Math14591419
FrontierMath (Tiers 1-3)57.2%—
FrontierMath Tier 424.4%—
OTIS Mock AIME 2024-202597.8%—
ProofBench31%—

Knowledge Grok 4.5 leads

Grok 4.5: 62.3 (#24), Grok 4 Fast: 32.0 (#214)

BenchmarkGrok 4.5Grok 4 Fast
LMArena Expert14661411
GPQA Diamond93.4%—
SimpleQA Verified48.3%—
Vectara Hallucination Rate—19.7%

Multimodal Not comparable

Grok 4.5: 37.6 (#72), Grok 4 Fast: —

BenchmarkGrok 4.5Grok 4 Fast
LMArena Vision1288—
Blueprint-Bench 227.3%—
Furniture Assembly22.5%—
LMArena Document1452—

Multilingual Grok 4.5 leads

Grok 4.5: 54.4 (#42), Grok 4 Fast: 51.3 (#111)

BenchmarkGrok 4.5Grok 4 Fast
LMArena Non-English14401396
LMArena Chinese14961457
LMArena French14561431
LMArena German14461383
LMArena Japanese14281352
LMArena Korean14041357
LMArena Russian14481389
LMArena Spanish14501415

Instruction Following Grok 4.5 leads

Grok 4.5: 76.0 (#48), Grok 4 Fast: 73.2 (#121)

BenchmarkGrok 4.5Grok 4 Fast
LMArena Instruction Following14461387

Long Context Grok 4 Fast leads

Grok 4.5: 44.8 (#56), Grok 4 Fast: 63.2 (#3)

BenchmarkGrok 4.5Grok 4 Fast
LMArena Longer Query14631415
Fiction.LiveBench—94.4%

Writing & Preference Grok 4.5 leads

Grok 4.5: 65.8 (#42), Grok 4 Fast: 60.0 (#102)

BenchmarkGrok 4.5Grok 4 Fast
LMArena Text14481407
LMArena Creative Writing14421387
LMArena Multi-Turn14561414
EQ-Bench Creative Writing1579—

Frequently asked questions

Is Grok 4.5 better than Grok 4 Fast?

Grok 4.5 is the stronger model overall, scoring 55.0 to 39.4 on the Noometry Index.

Is Grok 4.5 or Grok 4 Fast better for coding?

Grok 4.5 scores higher on coding benchmarks: 52.2 versus 32.5 in the Noometry coding category.

How many benchmarks do Grok 4.5 and Grok 4 Fast share?

26 benchmarks have published results for both models. Grok 4.5 has 52 scored results on Noometry and Grok 4 Fast has 30.

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