Model comparison

DeepSeek-V3.1-Terminus vs Grok 4.1 Fast

DeepSeek-V3.1-Terminus is the stronger model overall, scoring 43.1 to 41.4 on the Noometry Index. Grok 4.1 Fast costs 1.6× less per token, which makes it the better buy when DeepSeek-V3.1-Terminus's lead doesn't matter for your workload.

Last verified October 10, 2026. 12 shared benchmarks.

DeepSeek-V3.1-Terminus

DeepSeek

43.1

Rank #97 Confirmed

Grok 4.1 Fast xAI

41.4

Rank #136 Confirmed

Summary

They share 12 benchmarks with published results for both. DeepSeek-V3.1-Terminus scores higher in 6 categories and Grok 4.1 Fast in 1 category; 7 gaps are clear of the uncertainty.
The widest gap is in reasoning, where Grok 4.1 Fast leads 43.4 to 26.4.
The biggest single-benchmark swing is DTBench: 81.3% for DeepSeek-V3.1-Terminus and 87.7% for Grok 4.1 Fast.
Grok 4.1 Fast is cheaper at $0.20 / $0.50 per million input/output tokens, against $0.27 / $1 for DeepSeek-V3.1-Terminus.
DeepSeek-V3.1-Terminus accepts more context: 164K tokens versus 128K.
DeepSeek-V3.1-Terminus has downloadable open weights; the other is API-only.

Side by side

DeepSeek-V3.1-Terminus and Grok 4.1 Fast specifications
	DeepSeek-V3.1-Terminus	Grok 4.1 Fast
Provider	DeepSeek	xAI
Noometry Index	43.1	41.4
Released	2025-09-22	2025-06-27
Weights	Open	Proprietary
Context window	164K	128K
Max output	147K	30K
Input $ / M tokens	$0.27	$0.20
Output $ / M tokens	$1	$0.50
Results tracked	16	32

Sponsored placements are available on pages like this one. Advertise on Noometry

Category by category

Coding DeepSeek-V3.1-Terminus leads

DeepSeek-V3.1-Terminus: 42.0 (#113), Grok 4.1 Fast: 34.1 (#245)

Coding benchmarks
Benchmark	DeepSeek-V3.1-Terminus	Grok 4.1 Fast
LMArena Coding	1426	1411
ALE-Bench	745.17	394.93
LMArena WebDev	—	1242
SciCode	40.6%	—

Agentic & Tool Use Not comparable

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

Agentic & Tool Use benchmarks
Benchmark	DeepSeek-V3.1-Terminus	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-Terminus: 26.4 (#133), Grok 4.1 Fast: 43.4 (#49)

Reasoning benchmarks
Benchmark	DeepSeek-V3.1-Terminus	Grok 4.1 Fast
LMArena Hard Prompts	1426	1407
DTBench	81.3%	87.7%
SimpleBench	—	56%
Kagi LLM Benchmark	57.4%	—
NYT Connections (extended)	—	87.4%
CritPt	1.7%	—
LMCA	28.6%	—
ForecastBench	—	61

Math DeepSeek-V3.1-Terminus leads

DeepSeek-V3.1-Terminus: 38.5 (#137), Grok 4.1 Fast: 31.9 (#221)

Math benchmarks
Benchmark	DeepSeek-V3.1-Terminus	Grok 4.1 Fast
LMArena Math	1402	1408
MathArena Final-Answer Competitions	—	60.9%
ProofBench	—	4%

Knowledge Not comparable

DeepSeek-V3.1-Terminus: —, Grok 4.1 Fast: 33.1 (#207)

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

Multimodal Not comparable

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

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

Multilingual DeepSeek-V3.1-Terminus leads

DeepSeek-V3.1-Terminus: 52.1 (#92), Grok 4.1 Fast: 51.0 (#114)

Multilingual benchmarks
Benchmark	DeepSeek-V3.1-Terminus	Grok 4.1 Fast
LMArena Non-English	1407	1391
LMArena Russian	1436	1387
LMArena Chinese	—	1441
LMArena French	—	1415
LMArena German	—	1404
LMArena Japanese	—	1349
LMArena Korean	—	1361
LMArena Spanish	—	1413

Instruction Following DeepSeek-V3.1-Terminus leads

DeepSeek-V3.1-Terminus: 74.0 (#106), Grok 4.1 Fast: 72.7 (#133)

Instruction Following benchmarks
Benchmark	DeepSeek-V3.1-Terminus	Grok 4.1 Fast
LMArena Instruction Following	1404	1376

Long Context DeepSeek-V3.1-Terminus leads

DeepSeek-V3.1-Terminus: 43.4 (#97), Grok 4.1 Fast: 42.4 (#126)

Long Context benchmarks
Benchmark	DeepSeek-V3.1-Terminus	Grok 4.1 Fast
LMArena Longer Query	1421	1390

Writing & Preference DeepSeek-V3.1-Terminus leads

DeepSeek-V3.1-Terminus: 61.0 (#92), Grok 4.1 Fast: 57.2 (#131)

Writing & Preference benchmarks
Benchmark	DeepSeek-V3.1-Terminus	Grok 4.1 Fast
LMArena Text	1419	1408
LMArena Creative Writing	1403	1394
LMArena Multi-Turn	1411	1389
EQ-Bench Creative Writing	—	1327

Frequently asked questions

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

Which is cheaper, DeepSeek-V3.1-Terminus 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-Terminus lists at $0.27 and $1.

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

DeepSeek-V3.1-Terminus scores higher on coding benchmarks: 42.0 versus 34.1 in the Noometry coding category.

Which has the bigger context window?

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

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

12 benchmarks have published results for both models. DeepSeek-V3.1-Terminus has 16 scored results on Noometry and Grok 4.1 Fast has 32.