Model comparison

Claude Sonnet 5.5 vs DeepSeek-V3.1

Claude Sonnet 5.5 is the stronger model overall, scoring 61.9 to 42.8 on the Noometry Index. DeepSeek-V3.1 costs 9.4× 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 10, 2026. 13 shared benchmarks.

Claude Sonnet 5.5 Anthropic

61.9

Rank #10 Confirmed

DeepSeek-V3.1

DeepSeek

42.8

Rank #108 Confirmed

Summary

They share 13 benchmarks with published results for both. Claude Sonnet 5.5 scores higher in 8 categories and DeepSeek-V3.1 in 0 categories; 8 gaps are clear of the uncertainty.
The widest gap is in math, where Claude Sonnet 5.5 leads 87.9 to 38.9.
DeepSeek-V3.1 is cheaper at $0.25 / $0.95 per million input/output tokens, against $2 / $10 for Claude Sonnet 5.5.
Claude Sonnet 5.5 accepts more context: 1M tokens versus 164K.
DeepSeek-V3.1 has downloadable open weights; the other is API-only.

Side by side

Claude Sonnet 5.5 and DeepSeek-V3.1 specifications
	Claude Sonnet 5.5	DeepSeek-V3.1
Provider	Anthropic	DeepSeek
Noometry Index	61.9	42.8
Released	2026-09-28	2025-08-21
Weights	Proprietary	Open
Context window	1M	164K
Max output	128K	8K
Input $ / M tokens	$2	$0.25
Output $ / M tokens	$10	$0.95
Results tracked	32	27

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Category by category

Coding Claude Sonnet 5.5 leads

Claude Sonnet 5.5: 67.3 (#6), DeepSeek-V3.1: 40.3 (#144)

Coding benchmarks
Benchmark	Claude Sonnet 5.5	DeepSeek-V3.1
LMArena Coding	1513	1417
FrontierCode	52.1%	—
CursorBench	55.5%	—
LMArena WebDev	1774	—
FrontierSWE	61.9%	—
SciCode	61%	—
WeirdML	—	38.4%
ALE-Bench	1,819	—

Agentic & Tool Use Not comparable

Claude Sonnet 5.5: 45.0 (#16), DeepSeek-V3.1: —

Agentic & Tool Use benchmarks
Benchmark	Claude Sonnet 5.5	DeepSeek-V3.1
APEX-Agents	75.5%	—

Reasoning Claude Sonnet 5.5 leads

Claude Sonnet 5.5: 54.0 (#28), DeepSeek-V3.1: 27.9 (#110)

Reasoning benchmarks
Benchmark	Claude Sonnet 5.5	DeepSeek-V3.1
LMArena Hard Prompts	1495	1417
Epoch Capabilities Index	165.03	139.92
SimpleBench	—	40%
Kagi LLM Benchmark	—	53.2%
NYT Connections (extended)	80.5%	—
CritPt	31.4%	—
Mystery Game Puzzles	65%	—
DTBench	—	82.7%
LMCA	—	24.3%
ForecastBench	—	58

Math Claude Sonnet 5.5 leads

Claude Sonnet 5.5: 87.9 (#6), DeepSeek-V3.1: 38.9 (#122)

Math benchmarks
Benchmark	Claude Sonnet 5.5	DeepSeek-V3.1
LMArena Math	1510	1420
FrontierMath (Tiers 1-3)	88.8%	—
FrontierMath Tier 4	80.5%	—
OTIS Mock AIME 2024-2025	100%	—
ProofBench	100%	—
FrontierMath Erdős	2.9%	—

Knowledge Claude Sonnet 5.5 leads

Claude Sonnet 5.5: 66.0 (#12), DeepSeek-V3.1: 43.7 (#90)

Knowledge benchmarks
Benchmark	Claude Sonnet 5.5	DeepSeek-V3.1
LMArena Expert	1540	1405
GPQA Diamond	95.6%	—
SimpleQA Verified	46.5%	—
Vectara Hallucination Rate	—	5.5%

Multimodal Not comparable

Claude Sonnet 5.5: 51.5 (#6), DeepSeek-V3.1: —

Multimodal benchmarks
Benchmark	Claude Sonnet 5.5	DeepSeek-V3.1
LMArena Vision	1289	—
Furniture Assembly	75%	—

Multilingual Claude Sonnet 5.5 leads

Claude Sonnet 5.5: 55.3 (#30), DeepSeek-V3.1: 51.6 (#106)

Multilingual benchmarks
Benchmark	Claude Sonnet 5.5	DeepSeek-V3.1
LMArena Non-English	1452	1400
LMArena Chinese	1522	1469
LMArena Russian	1451	1405
LMArena French	—	1447
LMArena German	—	1411
LMArena Japanese	—	1378
LMArena Korean	—	1337
LMArena Spanish	—	1431

Instruction Following Claude Sonnet 5.5 leads

Claude Sonnet 5.5: 78.3 (#11), DeepSeek-V3.1: 73.9 (#110)

Instruction Following benchmarks
Benchmark	Claude Sonnet 5.5	DeepSeek-V3.1
LMArena Instruction Following	1495	1400

Long Context Claude Sonnet 5.5 leads

Claude Sonnet 5.5: 45.9 (#28), DeepSeek-V3.1: 36.3 (#232)

Long Context benchmarks
Benchmark	Claude Sonnet 5.5	DeepSeek-V3.1
LMArena Longer Query	1498	1422
Fiction.LiveBench	—	52.8%

Writing & Preference Claude Sonnet 5.5 leads

Claude Sonnet 5.5: 66.0 (#40), DeepSeek-V3.1: 60.3 (#98)

Writing & Preference benchmarks
Benchmark	Claude Sonnet 5.5	DeepSeek-V3.1
LMArena Text	1471	1420
LMArena Creative Writing	1465	1401
LMArena Multi-Turn	1474	1408
EQ-Bench Creative Writing	—	1436

Frequently asked questions

Is Claude Sonnet 5.5 better than DeepSeek-V3.1?

Which is cheaper, Claude Sonnet 5.5 or DeepSeek-V3.1?

DeepSeek-V3.1 is cheaper. It lists at $0.25 per million input tokens and $0.95 per million output tokens; Claude Sonnet 5.5 lists at $2 and $10.

Is Claude Sonnet 5.5 or DeepSeek-V3.1 better for coding?

Claude Sonnet 5.5 scores higher on coding benchmarks: 67.3 versus 40.3 in the Noometry coding category.

Which has the bigger context window?

Claude Sonnet 5.5 does, with 1M tokens against 164K.

How many benchmarks do Claude Sonnet 5.5 and DeepSeek-V3.1 share?

13 benchmarks have published results for both models. Claude Sonnet 5.5 has 32 scored results on Noometry and DeepSeek-V3.1 has 27.