Noometry

Model comparison

Claude Opus 5.5 vs Gemini 2.5 Flash

Claude Opus 5.5 is the stronger model overall, scoring 68.6 to 39.3 on the Noometry Index. Gemini 2.5 Flash costs 9.4× less per token, which makes it the better buy when Claude Opus 5.5's lead doesn't matter for your workload.

Last verified . 25 shared benchmarks.

Claude Opus 5.5 Anthropic

68.6

Rank #3 Confirmed

Gemini 2.5 Flash Google

39.3

Rank #170 Confirmed

Summary

  • They share 25 benchmarks with published results for both. Claude Opus 5.5 scores higher in 9 categories and Gemini 2.5 Flash in 1 category; 9 gaps are clear of the uncertainty.
  • The widest gap is in reasoning, where Claude Opus 5.5 leads 80.2 to 18.1.
  • The biggest single-benchmark swing is ARC-AGI-2: 93.3% for Claude Opus 5.5 and 2.5% for Gemini 2.5 Flash.
  • Gemini 2.5 Flash is cheaper at $0.30 / $2.50 per million input/output tokens, against $4 / $20 for Claude Opus 5.5.
  • Gemini 2.5 Flash accepts more context: 1.05M tokens versus 1M.

Side by side

Claude Opus 5.5Gemini 2.5 Flash
ProviderAnthropicGoogle
Noometry Index68.639.3
Released2026-09-222025-04-17
WeightsProprietaryProprietary
Context window1M1.05M
Max output128K66K
Input $ / M tokens$4$0.30
Output $ / M tokens$20$2.50
Results tracked4454

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Category by category

Coding Claude Opus 5.5 leads

Claude Opus 5.5: 71.9 (#3), Gemini 2.5 Flash: 35.8 (#220)

BenchmarkClaude Opus 5.5Gemini 2.5 Flash
LMArena Coding15471424
ALE-Bench2,147661.88
FrontierCode54.6%—
SWE-bench Verified (bash only)—28.7%
Aider Polyglot—55.1%
CursorBench57.8%—
LMArena WebDev1813—
FrontierSWE62.3%—
SciCode66.9%—
WeirdML—41.9%
MirrorCode77.4%—

Agentic & Tool Use Claude Opus 5.5 leads

Claude Opus 5.5: 45.3 (#15), Gemini 2.5 Flash: 30.8 (#74)

BenchmarkClaude Opus 5.5Gemini 2.5 Flash
Vending-Bench 29,235548.84
Terminal-Bench—17.1%
APEX-Agents73.5%—
Berkeley Function Calling Leaderboard—56.2%
TheAgentCompany—41.1%
BALROG—33.5%
GDP.pdf30.6%—

Reasoning Claude Opus 5.5 leads

Claude Opus 5.5: 80.2 (#3), Gemini 2.5 Flash: 18.1 (#286)

BenchmarkClaude Opus 5.5Gemini 2.5 Flash
ARC-AGI-293.3%2.5%
ARC-AGI-198.5%33.3%
CritPt31.7%1.1%
LMArena Hard Prompts15351422
DTBench98.9%76.5%
LMCA68.2%27.5%
Epoch Capabilities Index167.33143.03
SimpleBench—41.2%
Kagi LLM Benchmark—56.8%
NYT Connections (extended)88.5%—
EnigmaEval—2.7%
EBR-Bench71.4%—
Mystery Game Puzzles71%—
ForecastBench—60.6

Math Claude Opus 5.5 leads

Claude Opus 5.5: 91.8 (#3), Gemini 2.5 Flash: 39.9 (#98)

BenchmarkClaude Opus 5.5Gemini 2.5 Flash
OTIS Mock AIME 2024-2025100%73.1%
LMArena Math15061415
FrontierMath (Tiers 1-3)91.2%—
FrontierMath Tier 495%—
ProofBench100%—
Omni-MATH—38.5%
FrontierMath (Feb 2025 set)—4.8%
FrontierMath Erdős2.9%—
FrontierMath Tier 4 (v1)—4.2%

Knowledge Claude Opus 5.5 leads

Claude Opus 5.5: 66.4 (#10), Gemini 2.5 Flash: 36.4 (#168)

BenchmarkClaude Opus 5.5Gemini 2.5 Flash
LMArena Expert15471426
GPQA Diamond90.6%—
Humanity's Last Exam—12.1%
SimpleQA Verified72.2%—
MMLU-Pro—63.9%
Confabulations—16.8%
Vectara Hallucination Rate—7.8%
GPQA (HELM)—39%

Multimodal Claude Opus 5.5 leads

Claude Opus 5.5: 57.8 (#1), Gemini 2.5 Flash: 41.8 (#32)

BenchmarkClaude Opus 5.5Gemini 2.5 Flash
LMArena Vision13211253
GeoBench—76%
VPCT—46.2%
Blueprint-Bench 251.2%—
Furniture Assembly83.3%—
SpatialViz-Bench—36.9%

Multilingual Claude Opus 5.5 leads

Claude Opus 5.5: 59.1 (#2), Gemini 2.5 Flash: 52.3 (#88)

BenchmarkClaude Opus 5.5Gemini 2.5 Flash
LMArena Non-English15071409
LMArena Chinese15881450
LMArena French15141433
LMArena Russian15201415
LMArena Spanish15071421
LMArena German—1418
LMArena Japanese—1405
LMArena Korean—1385

Instruction Following Claude Opus 5.5 leads

Claude Opus 5.5: 80.0 (#3), Gemini 2.5 Flash: 75.7 (#54)

BenchmarkClaude Opus 5.5Gemini 2.5 Flash
LMArena Instruction Following15371405
IFEval—89.8%

Long Context Too close to call

Claude Opus 5.5: 47.1 (#19), Gemini 2.5 Flash: 47.5 (#17)

BenchmarkClaude Opus 5.5Gemini 2.5 Flash
LMArena Longer Query15321419
Fiction.LiveBench—77.8%

Writing & Preference Claude Opus 5.5 leads

Claude Opus 5.5: 78.2 (#3), Gemini 2.5 Flash: 53.8 (#157)

BenchmarkClaude Opus 5.5Gemini 2.5 Flash
LMArena Text15151417
LMArena Creative Writing15331400
EQ-Bench Creative Writing20501137
LMArena Multi-Turn14991408
Short-Story Creative Writing—76.5%
WildBench—81.7%

Frequently asked questions

Is Claude Opus 5.5 better than Gemini 2.5 Flash?

Claude Opus 5.5 is the stronger model overall, scoring 68.6 to 39.3 on the Noometry Index. Gemini 2.5 Flash costs 9.4× 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 Gemini 2.5 Flash?

Gemini 2.5 Flash is cheaper. It lists at $0.30 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 Gemini 2.5 Flash better for coding?

Claude Opus 5.5 scores higher on coding benchmarks: 71.9 versus 35.8 in the Noometry coding category.

Which has the bigger context window?

Gemini 2.5 Flash does, with 1.05M tokens against 1M.

How many benchmarks do Claude Opus 5.5 and Gemini 2.5 Flash share?

25 benchmarks have published results for both models. Claude Opus 5.5 has 44 scored results on Noometry and Gemini 2.5 Flash has 54.

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