Model comparison

DeepSeek-V3.1 vs Grok 4.1 Fast

DeepSeek-V3.1 is the stronger model overall, scoring 42.8 to 41.4 on the Noometry Index. Grok 4.1 Fast costs 1.5× less per token, which makes it the better buy when DeepSeek-V3.1's lead doesn't matter for your workload.

Last verified October 10, 2026. 22 shared benchmarks.

DeepSeek-V3.1

DeepSeek

42.8

Rank #108 Confirmed

Grok 4.1 Fast xAI

41.4

Rank #136 Confirmed

Summary

They share 22 benchmarks with published results for both. DeepSeek-V3.1 scores higher in 6 categories and Grok 4.1 Fast in 2 categories; 7 gaps are clear of the uncertainty.
The widest gap is in reasoning, where Grok 4.1 Fast leads 43.4 to 27.9.
The biggest single-benchmark swing is SimpleBench: 40% for DeepSeek-V3.1 and 56% for Grok 4.1 Fast.
Grok 4.1 Fast is cheaper at $0.20 / $0.50 per million input/output tokens, against $0.25 / $0.95 for DeepSeek-V3.1.
DeepSeek-V3.1 accepts more context: 164K tokens versus 128K.
DeepSeek-V3.1 has downloadable open weights; the other is API-only.

Side by side

DeepSeek-V3.1 and Grok 4.1 Fast specifications
	DeepSeek-V3.1	Grok 4.1 Fast
Provider	DeepSeek	xAI
Noometry Index	42.8	41.4
Released	2025-08-21	2025-06-27
Weights	Open	Proprietary
Context window	164K	128K
Max output	8K	30K
Input $ / M tokens	$0.25	$0.20
Output $ / M tokens	$0.95	$0.50
Results tracked	27	32

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Category by category

Coding DeepSeek-V3.1 leads

DeepSeek-V3.1: 40.3 (#144), Grok 4.1 Fast: 34.1 (#245)

Coding benchmarks
Benchmark	DeepSeek-V3.1	Grok 4.1 Fast
LMArena Coding	1417	1411
LMArena WebDev	—	1242
WeirdML	38.4%	—
ALE-Bench	—	394.93

Agentic & Tool Use Not comparable

DeepSeek-V3.1: —, Grok 4.1 Fast: 36.3 (#39)

Agentic & Tool Use benchmarks
Benchmark	DeepSeek-V3.1	Grok 4.1 Fast
Berkeley Function Calling Leaderboard	—	69.6%
τ²-bench Banking	—	13.1%
LMArena Search	—	1171
Vending-Bench 2	—	1,107

Reasoning Grok 4.1 Fast leads

DeepSeek-V3.1: 27.9 (#110), Grok 4.1 Fast: 43.4 (#49)

Reasoning benchmarks
Benchmark	DeepSeek-V3.1	Grok 4.1 Fast
SimpleBench	40%	56%
LMArena Hard Prompts	1417	1407
DTBench	82.7%	87.7%
ForecastBench	58	61
Kagi LLM Benchmark	53.2%	—
NYT Connections (extended)	—	87.4%
LMCA	24.3%	—
Epoch Capabilities Index	139.92	—

Math DeepSeek-V3.1 leads

DeepSeek-V3.1: 38.9 (#122), Grok 4.1 Fast: 31.9 (#221)

Math benchmarks
Benchmark	DeepSeek-V3.1	Grok 4.1 Fast
LMArena Math	1420	1408
MathArena Final-Answer Competitions	—	60.9%
ProofBench	—	4%

Knowledge DeepSeek-V3.1 leads

DeepSeek-V3.1: 43.7 (#90), Grok 4.1 Fast: 33.1 (#207)

Knowledge benchmarks
Benchmark	DeepSeek-V3.1	Grok 4.1 Fast
Vectara Hallucination Rate	5.5%	17.8%
LMArena Expert	1405	1399

Multimodal Not comparable

DeepSeek-V3.1: —, Grok 4.1 Fast: 37.0 (#76)

Multimodal benchmarks
Benchmark	DeepSeek-V3.1	Grok 4.1 Fast
LMArena Vision	—	1201

Multilingual Too close to call

DeepSeek-V3.1: 51.6 (#106), Grok 4.1 Fast: 51.0 (#114)

Multilingual benchmarks
Benchmark	DeepSeek-V3.1	Grok 4.1 Fast
LMArena Non-English	1400	1391
LMArena Chinese	1469	1441
LMArena French	1447	1415
LMArena German	1411	1404
LMArena Japanese	1378	1349
LMArena Korean	1337	1361
LMArena Russian	1405	1387
LMArena Spanish	1431	1413

Instruction Following DeepSeek-V3.1 leads

DeepSeek-V3.1: 73.9 (#110), Grok 4.1 Fast: 72.7 (#133)

Instruction Following benchmarks
Benchmark	DeepSeek-V3.1	Grok 4.1 Fast
LMArena Instruction Following	1400	1376

Long Context Grok 4.1 Fast leads

DeepSeek-V3.1: 36.3 (#232), Grok 4.1 Fast: 42.4 (#126)

Long Context benchmarks
Benchmark	DeepSeek-V3.1	Grok 4.1 Fast
LMArena Longer Query	1422	1390
Fiction.LiveBench	52.8%	—

Writing & Preference DeepSeek-V3.1 leads

DeepSeek-V3.1: 60.3 (#98), Grok 4.1 Fast: 57.2 (#131)

Writing & Preference benchmarks
Benchmark	DeepSeek-V3.1	Grok 4.1 Fast
LMArena Text	1420	1408
LMArena Creative Writing	1401	1394
EQ-Bench Creative Writing	1436	1327
LMArena Multi-Turn	1408	1389

Frequently asked questions

Is DeepSeek-V3.1 better than Grok 4.1 Fast?

Which is cheaper, DeepSeek-V3.1 or Grok 4.1 Fast?

Grok 4.1 Fast is cheaper. It lists at $0.20 per million input tokens and $0.50 per million output tokens; DeepSeek-V3.1 lists at $0.25 and $0.95.

Is DeepSeek-V3.1 or Grok 4.1 Fast better for coding?

DeepSeek-V3.1 scores higher on coding benchmarks: 40.3 versus 34.1 in the Noometry coding category.

Which has the bigger context window?

DeepSeek-V3.1 does, with 164K tokens against 128K.

How many benchmarks do DeepSeek-V3.1 and Grok 4.1 Fast share?

22 benchmarks have published results for both models. DeepSeek-V3.1 has 27 scored results on Noometry and Grok 4.1 Fast has 32.