Model comparison

Claude Sonnet 5.5 vs Gemini 2.5 Flash

Claude Sonnet 5.5 is the stronger model overall, scoring 61.9 to 39.3 on the Noometry Index. Gemini 2.5 Flash costs 4.7× less per token, which makes it the better buy when Claude Sonnet 5.5's lead doesn't matter for your workload.

Last verified October 11, 2026. 17 shared benchmarks.

Claude Sonnet 5.5 Anthropic

61.9

Rank #10 Confirmed

Gemini 2.5 Flash

Google

39.3

Rank #170 Confirmed

Summary

They share 17 benchmarks with published results for both. Claude Sonnet 5.5 scores higher in 9 categories and Gemini 2.5 Flash in 1 category; 10 gaps are clear of the uncertainty.
The widest gap is in math, where Claude Sonnet 5.5 leads 87.9 to 39.9.
The biggest single-benchmark swing is CritPt: 31.4% for Claude Sonnet 5.5 and 1.1% for Gemini 2.5 Flash.
Gemini 2.5 Flash is cheaper at $0.30 / $2.50 per million input/output tokens, against $2 / $10 for Claude Sonnet 5.5.
Gemini 2.5 Flash accepts more context: 1.05M tokens versus 1M.

Side by side

Claude Sonnet 5.5 and Gemini 2.5 Flash specifications
	Claude Sonnet 5.5	Gemini 2.5 Flash
Provider	Anthropic	Google
Noometry Index	61.9	39.3
Released	2026-09-28	2025-04-17
Weights	Proprietary	Proprietary
Context window	1M	1.05M
Max output	128K	66K
Input $ / M tokens	$2	$0.30
Output $ / M tokens	$10	$2.50
Results tracked	32	54

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Category by category

Coding Claude Sonnet 5.5 leads

Claude Sonnet 5.5: 67.3 (#6), Gemini 2.5 Flash: 35.8 (#220)

Coding benchmarks
Benchmark	Claude Sonnet 5.5	Gemini 2.5 Flash
LMArena Coding	1513	1424
ALE-Bench	1,819	661.88
FrontierCode	52.1%	—
SWE-bench Verified (bash only)	—	28.7%
Aider Polyglot	—	55.1%
CursorBench	55.5%	—
LMArena WebDev	1774	—
FrontierSWE	61.9%	—
SciCode	61%	—
WeirdML	—	41.9%

Agentic & Tool Use Claude Sonnet 5.5 leads

Claude Sonnet 5.5: 45.0 (#16), Gemini 2.5 Flash: 30.8 (#74)

Agentic & Tool Use benchmarks
Benchmark	Claude Sonnet 5.5	Gemini 2.5 Flash
Terminal-Bench	—	17.1%
APEX-Agents	75.5%	—
Berkeley Function Calling Leaderboard	—	56.2%
TheAgentCompany	—	41.1%
BALROG	—	33.5%
Vending-Bench 2	—	548.84

Reasoning Claude Sonnet 5.5 leads

Claude Sonnet 5.5: 54.0 (#28), Gemini 2.5 Flash: 18.1 (#286)

Reasoning benchmarks
Benchmark	Claude Sonnet 5.5	Gemini 2.5 Flash
CritPt	31.4%	1.1%
LMArena Hard Prompts	1495	1422
Epoch Capabilities Index	165.03	143.03
ARC-AGI-2	—	2.5%
SimpleBench	—	41.2%
Kagi LLM Benchmark	—	56.8%
NYT Connections (extended)	80.5%	—
ARC-AGI-1	—	33.3%
EnigmaEval	—	2.7%
Mystery Game Puzzles	65%	—
DTBench	—	76.5%
LMCA	—	27.5%
ForecastBench	—	60.6

Math Claude Sonnet 5.5 leads

Claude Sonnet 5.5: 87.9 (#6), Gemini 2.5 Flash: 39.9 (#98)

Math benchmarks
Benchmark	Claude Sonnet 5.5	Gemini 2.5 Flash
OTIS Mock AIME 2024-2025	100%	73.1%
LMArena Math	1510	1415
FrontierMath (Tiers 1-3)	88.8%	—
FrontierMath Tier 4	80.5%	—
ProofBench	100%	—
Omni-MATH	—	38.5%
FrontierMath (Feb 2025 set)	—	4.8%
FrontierMath Erdős	2.9%	—
FrontierMath Tier 4 (v1)	—	4.2%

Knowledge Claude Sonnet 5.5 leads

Claude Sonnet 5.5: 66.0 (#12), Gemini 2.5 Flash: 36.4 (#168)

Knowledge benchmarks
Benchmark	Claude Sonnet 5.5	Gemini 2.5 Flash
LMArena Expert	1540	1426
GPQA Diamond	95.6%	—
Humanity's Last Exam	—	12.1%
SimpleQA Verified	46.5%	—
MMLU-Pro	—	63.9%
Confabulations	—	16.8%
Vectara Hallucination Rate	—	7.8%
GPQA (HELM)	—	39%

Multimodal Claude Sonnet 5.5 leads

Claude Sonnet 5.5: 51.5 (#6), Gemini 2.5 Flash: 41.8 (#32)

Multimodal benchmarks
Benchmark	Claude Sonnet 5.5	Gemini 2.5 Flash
LMArena Vision	1289	1253
GeoBench	—	76%
VPCT	—	46.2%
Furniture Assembly	75%	—
SpatialViz-Bench	—	36.9%

Multilingual Claude Sonnet 5.5 leads

Claude Sonnet 5.5: 55.3 (#30), Gemini 2.5 Flash: 52.3 (#88)

Multilingual benchmarks
Benchmark	Claude Sonnet 5.5	Gemini 2.5 Flash
LMArena Non-English	1452	1409
LMArena Chinese	1522	1450
LMArena Russian	1451	1415
LMArena French	—	1433
LMArena German	—	1418
LMArena Japanese	—	1405
LMArena Korean	—	1385
LMArena Spanish	—	1421

Instruction Following Claude Sonnet 5.5 leads

Claude Sonnet 5.5: 78.3 (#11), Gemini 2.5 Flash: 75.7 (#54)

Instruction Following benchmarks
Benchmark	Claude Sonnet 5.5	Gemini 2.5 Flash
LMArena Instruction Following	1495	1405
IFEval	—	89.8%

Long Context Gemini 2.5 Flash leads

Claude Sonnet 5.5: 45.9 (#28), Gemini 2.5 Flash: 47.5 (#17)

Long Context benchmarks
Benchmark	Claude Sonnet 5.5	Gemini 2.5 Flash
LMArena Longer Query	1498	1419
Fiction.LiveBench	—	77.8%

Writing & Preference Claude Sonnet 5.5 leads

Claude Sonnet 5.5: 66.0 (#40), Gemini 2.5 Flash: 53.8 (#157)

Writing & Preference benchmarks
Benchmark	Claude Sonnet 5.5	Gemini 2.5 Flash
LMArena Text	1471	1417
LMArena Creative Writing	1465	1400
LMArena Multi-Turn	1474	1408
Short-Story Creative Writing	—	76.5%
EQ-Bench Creative Writing	—	1137
WildBench	—	81.7%

Frequently asked questions

Is Claude Sonnet 5.5 better than Gemini 2.5 Flash?

Which is cheaper, Claude Sonnet 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 Sonnet 5.5 lists at $2 and $10.

Is Claude Sonnet 5.5 or Gemini 2.5 Flash better for coding?

Claude Sonnet 5.5 scores higher on coding benchmarks: 67.3 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 Sonnet 5.5 and Gemini 2.5 Flash share?

17 benchmarks have published results for both models. Claude Sonnet 5.5 has 32 scored results on Noometry and Gemini 2.5 Flash has 54.