Noometry

Model comparison

Claude Opus 5.5 vs Grok 4.3

Claude Opus 5.5 is the stronger model overall, scoring 68.6 to 43.8 on the Noometry Index. Grok 4.3 costs 5.1× less per token, which makes it the better buy when Claude Opus 5.5's lead doesn't matter for your workload.

Last verified . 32 shared benchmarks.

Claude Opus 5.5 Anthropic

68.6

Rank #3 Confirmed

Grok 4.3 xAI

43.8

Rank #86 Confirmed

Summary

  • They share 32 benchmarks with published results for both. Claude Opus 5.5 scores higher in 10 categories and Grok 4.3 in 0 categories; 10 gaps are clear of the uncertainty.
  • The widest gap is in math, where Claude Opus 5.5 leads 91.8 to 46.0.
  • The biggest single-benchmark swing is ProofBench: 100% for Claude Opus 5.5 and 11% for Grok 4.3.
  • Grok 4.3 is cheaper at $1.25 / $2.50 per million input/output tokens, against $4 / $20 for Claude Opus 5.5.

Side by side

Claude Opus 5.5Grok 4.3
ProviderAnthropicxAI
Noometry Index68.643.8
Released2026-09-222026-04-17
WeightsProprietaryProprietary
Context window1M1M
Max output128K30K
Input $ / M tokens$4$1.25
Output $ / M tokens$20$2.50
Results tracked4440

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Category by category

Coding Claude Opus 5.5 leads

Claude Opus 5.5: 71.9 (#3), Grok 4.3: 41.6 (#121)

BenchmarkClaude Opus 5.5Grok 4.3
LMArena WebDev18131357
SciCode66.9%47.3%
LMArena Coding15471415
ALE-Bench2,147944.17
FrontierCode54.6%—
CursorBench57.8%—
FrontierSWE62.3%—
WeirdML—49.9%
MirrorCode77.4%—

Agentic & Tool Use Claude Opus 5.5 leads

Claude Opus 5.5: 45.3 (#15), Grok 4.3: 27.7 (#99)

BenchmarkClaude Opus 5.5Grok 4.3
GDP.pdf30.6%8%
Vending-Bench 29,23535.26
APEX-Agents73.5%—
LMArena Search—1165

Reasoning Claude Opus 5.5 leads

Claude Opus 5.5: 80.2 (#3), Grok 4.3: 35.9 (#68)

BenchmarkClaude Opus 5.5Grok 4.3
NYT Connections (extended)88.5%55.2%
CritPt31.7%8%
LMArena Hard Prompts15351396
DTBench98.9%90.7%
LMCA68.2%38.3%
Epoch Capabilities Index167.33149.16
ARC-AGI-293.3%—
ARC-AGI-198.5%—
Chess Puzzles—25%
EBR-Bench71.4%—
Mystery Game Puzzles71%—
ForecastBench—60.3

Math Claude Opus 5.5 leads

Claude Opus 5.5: 91.8 (#3), Grok 4.3: 46.0 (#74)

BenchmarkClaude Opus 5.5Grok 4.3
FrontierMath (Tiers 1-3)91.2%42.8%
FrontierMath Tier 495%14.6%
OTIS Mock AIME 2024-2025100%93.3%
ProofBench100%11%
LMArena Math15061388
FrontierMath Erdős2.9%—

Knowledge Claude Opus 5.5 leads

Claude Opus 5.5: 66.4 (#10), Grok 4.3: 52.5 (#62)

BenchmarkClaude Opus 5.5Grok 4.3
GPQA Diamond90.6%88.8%
SimpleQA Verified72.2%33.2%
LMArena Expert15471385

Multimodal Claude Opus 5.5 leads

Claude Opus 5.5: 57.8 (#1), Grok 4.3: 31.6 (#104)

BenchmarkClaude Opus 5.5Grok 4.3
LMArena Vision13211229
Blueprint-Bench 251.2%0%
Furniture Assembly83.3%—

Multilingual Claude Opus 5.5 leads

Claude Opus 5.5: 59.1 (#2), Grok 4.3: 50.5 (#120)

BenchmarkClaude Opus 5.5Grok 4.3
LMArena Non-English15071385
LMArena Chinese15881422
LMArena French15141412
LMArena Russian15201399
LMArena Spanish15071398
LMArena German—1395
LMArena Japanese—1379
LMArena Korean—1356

Instruction Following Claude Opus 5.5 leads

Claude Opus 5.5: 80.0 (#3), Grok 4.3: 72.1 (#140)

BenchmarkClaude Opus 5.5Grok 4.3
LMArena Instruction Following15371366

Long Context Claude Opus 5.5 leads

Claude Opus 5.5: 47.1 (#19), Grok 4.3: 42.5 (#123)

BenchmarkClaude Opus 5.5Grok 4.3
LMArena Longer Query15321393

Writing & Preference Claude Opus 5.5 leads

Claude Opus 5.5: 78.2 (#3), Grok 4.3: 58.5 (#118)

BenchmarkClaude Opus 5.5Grok 4.3
LMArena Text15151397
LMArena Creative Writing15331380
LMArena Multi-Turn14991406
EQ-Bench Creative Writing2050—
EQ-Bench 4—1075

Frequently asked questions

Is Claude Opus 5.5 better than Grok 4.3?

Claude Opus 5.5 is the stronger model overall, scoring 68.6 to 43.8 on the Noometry Index. Grok 4.3 costs 5.1× less per token, which makes it the better buy when Claude Opus 5.5's lead doesn't matter for your workload.

Which is cheaper, Claude Opus 5.5 or Grok 4.3?

Grok 4.3 is cheaper. It lists at $1.25 per million input tokens and $2.50 per million output tokens; Claude Opus 5.5 lists at $4 and $20.

Is Claude Opus 5.5 or Grok 4.3 better for coding?

Claude Opus 5.5 scores higher on coding benchmarks: 71.9 versus 41.6 in the Noometry coding category.

Which has the bigger context window?

Both accept 1M tokens.

How many benchmarks do Claude Opus 5.5 and Grok 4.3 share?

32 benchmarks have published results for both models. Claude Opus 5.5 has 44 scored results on Noometry and Grok 4.3 has 40.

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