Noometry

Model comparison

Claude Sonnet 5.5 vs Grok 4 Fast

Claude Sonnet 5.5 is the stronger model overall, scoring 60.5 to 39.0 on the Noometry Index.

Last verified . 1 shared benchmarks.

Claude Sonnet 5.5 Anthropic

60.5

Rank #10 Confirmed

Grok 4 Fast xAI

39.0

Rank #164 Confirmed

Summary

  • They share 1 benchmark with published results for both. Claude Sonnet 5.5 scores higher in 5 categories and Grok 4 Fast in 0 categories; 5 gaps are clear of the uncertainty.
  • The widest gap is in math, where Claude Sonnet 5.5 leads 88.7 to 36.1.

Side by side

Claude Sonnet 5.5Grok 4 Fast
ProviderAnthropicxAI
Noometry Index60.539.0
Released2026-09-282025-09-19
WeightsProprietaryProprietary
Context window1M—
Max output128K—
Input $ / M tokens$2—
Output $ / M tokens$10—
Results tracked1630

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Category by category

Coding Claude Sonnet 5.5 leads

Claude Sonnet 5.5: 65.5 (#6), Grok 4 Fast: 32.3 (#264)

BenchmarkClaude Sonnet 5.5Grok 4 Fast
LMArena WebDev16991160
FrontierCode52.1%—
CursorBench55.5%—
FrontierSWE61.9%—
SciCode61%—
WeirdML—42.9%
LMArena Coding—1429
ALE-Bench1,819—

Agentic & Tool Use Claude Sonnet 5.5 leads

Claude Sonnet 5.5: 44.9 (#14), Grok 4 Fast: 29.3 (#80)

BenchmarkClaude Sonnet 5.5Grok 4 Fast
APEX-Agents75.5%—
τ²-bench Banking—15.7%
Cybench—30%
LMArena Search—1171

Reasoning Claude Sonnet 5.5 leads

Claude Sonnet 5.5: 52.4 (#29), Grok 4 Fast: 22.5 (#179)

BenchmarkClaude Sonnet 5.5Grok 4 Fast
ARC-AGI-2—5.3%
Kagi LLM Benchmark—66.1%
ARC-AGI-1—48.5%
CritPt31.4%—
LMArena Hard Prompts—1413
Mystery Game Puzzles65%—
DTBench—82.7%
Epoch Capabilities Index—144.21
ForecastBench—60.5

Math Claude Sonnet 5.5 leads

Claude Sonnet 5.5: 88.7 (#4), Grok 4 Fast: 36.1 (#126)

BenchmarkClaude Sonnet 5.5Grok 4 Fast
FrontierMath (Tiers 1-3)88.8%—
FrontierMath Tier 480.5%—
OTIS Mock AIME 2024-2025100%—
ProofBench100%—
LMArena Math—1419

Knowledge Claude Sonnet 5.5 leads

Claude Sonnet 5.5: 66.0 (#11), Grok 4 Fast: 31.5 (#211)

BenchmarkClaude Sonnet 5.5Grok 4 Fast
GPQA Diamond95.6%—
SimpleQA Verified46.5%—
Vectara Hallucination Rate—19.7%
LMArena Expert—1411

Multimodal Not comparable

Claude Sonnet 5.5: 53.2 (#5), Grok 4 Fast: —

BenchmarkClaude Sonnet 5.5Grok 4 Fast
Furniture Assembly75%—

Multilingual Not comparable

Claude Sonnet 5.5: —, Grok 4 Fast: 51.5 (#106)

BenchmarkClaude Sonnet 5.5Grok 4 Fast
LMArena Non-English—1397
LMArena Chinese—1458
LMArena French—1433
LMArena German—1383
LMArena Japanese—1358
LMArena Korean—1359
LMArena Russian—1387
LMArena Spanish—1414

Instruction Following Not comparable

Claude Sonnet 5.5: —, Grok 4 Fast: 73.4 (#116)

BenchmarkClaude Sonnet 5.5Grok 4 Fast
LMArena Instruction Following—1388

Long Context Not comparable

Claude Sonnet 5.5: —, Grok 4 Fast: 63.2 (#3)

BenchmarkClaude Sonnet 5.5Grok 4 Fast
Fiction.LiveBench—94.4%
LMArena Longer Query—1415

Writing & Preference Not comparable

Claude Sonnet 5.5: —, Grok 4 Fast: 60.2 (#96)

BenchmarkClaude Sonnet 5.5Grok 4 Fast
LMArena Text—1407
LMArena Creative Writing—1388
LMArena Multi-Turn—1414

Frequently asked questions

Is Claude Sonnet 5.5 better than Grok 4 Fast?

Claude Sonnet 5.5 is the stronger model overall, scoring 60.5 to 39.0 on the Noometry Index.

Is Claude Sonnet 5.5 or Grok 4 Fast better for coding?

Claude Sonnet 5.5 scores higher on coding benchmarks: 65.5 versus 32.3 in the Noometry coding category.

How many benchmarks do Claude Sonnet 5.5 and Grok 4 Fast share?

1 benchmark has published results for both models. Claude Sonnet 5.5 has 16 scored results on Noometry and Grok 4 Fast has 30.

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