Noometry

Model comparison

Grok 4.1 Fast vs Mercury 2

Grok 4.1 Fast is the stronger model overall, scoring 41.4 to 39.1 on the Noometry Index.

Last verified . 14 shared benchmarks.

Grok 4.1 Fast xAI

41.4

Rank #136 Confirmed

Mercury 2 Inception

39.1

Rank #175 Confirmed

Summary

  • They share 14 benchmarks with published results for both. Grok 4.1 Fast scores higher in 6 categories and Mercury 2 in 1 category; 6 gaps are clear of the uncertainty.
  • The widest gap is in reasoning, where Grok 4.1 Fast leads 43.4 to 23.8.
  • The biggest single-benchmark swing is Vectara Hallucination Rate: 17.8% for Grok 4.1 Fast and 12.3% for Mercury 2.
  • Grok 4.1 Fast is cheaper at $0.20 / $0.50 per million input/output tokens, against $0.25 / $0.75 for Mercury 2.

Side by side

Grok 4.1 FastMercury 2
ProviderxAIInception
Noometry Index41.439.1
Released2025-06-272026-02-20
WeightsProprietaryProprietary
Context window128K128K
Max output30K50K
Input $ / M tokens$0.20$0.25
Output $ / M tokens$0.50$0.75
Results tracked3217

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Category by category

Coding Too close to call

Grok 4.1 Fast: 34.1 (#245), Mercury 2: 33.5 (#255)

BenchmarkGrok 4.1 FastMercury 2
LMArena WebDev12421171
LMArena Coding14111391
ALE-Bench394.93785.58
SciCode—38.7%
WeirdML—43.2%

Agentic & Tool Use Not comparable

Grok 4.1 Fast: 36.3 (#39), Mercury 2: —

BenchmarkGrok 4.1 FastMercury 2
Berkeley Function Calling Leaderboard69.6%—
τ²-bench Banking13.1%—
LMArena Search1171—
Vending-Bench 21,107—

Reasoning Grok 4.1 Fast leads

Grok 4.1 Fast: 43.4 (#49), Mercury 2: 23.8 (#170)

BenchmarkGrok 4.1 FastMercury 2
LMArena Hard Prompts14071362
SimpleBench56%—
NYT Connections (extended)87.4%—
CritPt—0.8%
DTBench87.7%—
ForecastBench61—

Math Not comparable

Grok 4.1 Fast: 31.9 (#221), Mercury 2: —

BenchmarkGrok 4.1 FastMercury 2
MathArena Final-Answer Competitions60.9%—
ProofBench4%—
LMArena Math1408—

Knowledge Mercury 2 leads

Grok 4.1 Fast: 33.1 (#207), Mercury 2: 36.2 (#172)

BenchmarkGrok 4.1 FastMercury 2
Vectara Hallucination Rate17.8%12.3%
LMArena Expert13991358

Multimodal Not comparable

Grok 4.1 Fast: 37.0 (#76), Mercury 2: —

BenchmarkGrok 4.1 FastMercury 2
LMArena Vision1201—

Multilingual Grok 4.1 Fast leads

Grok 4.1 Fast: 51.0 (#114), Mercury 2: 46.6 (#157)

BenchmarkGrok 4.1 FastMercury 2
LMArena Non-English13911331
LMArena Chinese14411417
LMArena Russian13871304
LMArena French1415—
LMArena German1404—
LMArena Japanese1349—
LMArena Korean1361—
LMArena Spanish1413—

Instruction Following Grok 4.1 Fast leads

Grok 4.1 Fast: 72.7 (#133), Mercury 2: 70.2 (#165)

BenchmarkGrok 4.1 FastMercury 2
LMArena Instruction Following13761329

Long Context Grok 4.1 Fast leads

Grok 4.1 Fast: 42.4 (#126), Mercury 2: 40.5 (#154)

BenchmarkGrok 4.1 FastMercury 2
LMArena Longer Query13901330

Writing & Preference Grok 4.1 Fast leads

Grok 4.1 Fast: 57.2 (#131), Mercury 2: 53.8 (#155)

BenchmarkGrok 4.1 FastMercury 2
LMArena Text14081355
LMArena Creative Writing13941289
LMArena Multi-Turn13891358
EQ-Bench Creative Writing1327—

Frequently asked questions

Is Grok 4.1 Fast better than Mercury 2?

Grok 4.1 Fast is the stronger model overall, scoring 41.4 to 39.1 on the Noometry Index.

Which is cheaper, Grok 4.1 Fast or Mercury 2?

Grok 4.1 Fast is cheaper. It lists at $0.20 per million input tokens and $0.50 per million output tokens; Mercury 2 lists at $0.25 and $0.75.

Is Grok 4.1 Fast or Mercury 2 better for coding?

They score almost the same on coding (34.1 vs 33.5); test both on your own repository before choosing.

Which has the bigger context window?

Both accept 128K tokens.

How many benchmarks do Grok 4.1 Fast and Mercury 2 share?

14 benchmarks have published results for both models. Grok 4.1 Fast has 32 scored results on Noometry and Mercury 2 has 17.

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