Noometry

Model comparison

Grok 4.1 Fast vs Mercury 2.5

Grok 4.1 Fast has enough public results to be ranked (#131); Mercury 2.5 does not yet, so treat this comparison as directional.

Last verified . 2 shared benchmarks.

Grok 4.1 Fast xAI

40.9

Rank #131 Confirmed

Mercury 2.5 Inception

30.2

Unranked Sparse

Summary

  • They share 2 benchmarks with published results for both. Grok 4.1 Fast scores higher in 1 category and Mercury 2.5 in 0 categories; one gap is clear of the uncertainty.
  • The widest gap is in math, where Grok 4.1 Fast leads 30.9 to 22.4.
  • Mercury 2.5 is cheaper at $0.04 / $0.15 per million input/output tokens, against $0.20 / $0.50 for Grok 4.1 Fast.
  • Mercury 2.5 accepts more context: 260K tokens versus 128K.

Side by side

Grok 4.1 FastMercury 2.5
ProviderxAIInception
Noometry Index40.930.2
Released2025-06-272026-09-08
WeightsProprietaryProprietary
Context window128K260K
Max output30K66K
Input $ / M tokens$0.20$0.04
Output $ / M tokens$0.50$0.15
Results tracked322

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Category by category

Coding Not comparable

Grok 4.1 Fast: 33.8 (#236), Mercury 2.5: —

BenchmarkGrok 4.1 FastMercury 2.5
ALE-Bench394.93301.65
LMArena WebDev1241—
LMArena Coding1411—

Agentic & Tool Use Not comparable

Grok 4.1 Fast: 36.1 (#35), Mercury 2.5: —

BenchmarkGrok 4.1 FastMercury 2.5
Berkeley Function Calling Leaderboard69.6%—
τ²-bench Banking13.1%—
LMArena Search1171—
Vending-Bench 21,107—

Reasoning Not comparable

Grok 4.1 Fast: 42.3 (#45), Mercury 2.5: —

BenchmarkGrok 4.1 FastMercury 2.5
SimpleBench56%—
NYT Connections (extended)87.4%—
LMArena Hard Prompts1407—
DTBench87.7%—
ForecastBench61—

Math Grok 4.1 Fast leads

Grok 4.1 Fast: 30.9 (#201), Mercury 2.5: 22.4

BenchmarkGrok 4.1 FastMercury 2.5
ProofBench4%3%
MathArena Final-Answer Competitions60.9%—
LMArena Math1408—

Knowledge Not comparable

Grok 4.1 Fast: 32.6 (#203), Mercury 2.5: —

BenchmarkGrok 4.1 FastMercury 2.5
Vectara Hallucination Rate17.8%—
LMArena Expert1398—

Multimodal Not comparable

Grok 4.1 Fast: 36.3 (#71), Mercury 2.5: —

BenchmarkGrok 4.1 FastMercury 2.5
LMArena Vision1201—

Multilingual Not comparable

Grok 4.1 Fast: 51.1 (#110), Mercury 2.5: —

BenchmarkGrok 4.1 FastMercury 2.5
LMArena Non-English1391—
LMArena Chinese1441—
LMArena French1416—
LMArena German1404—
LMArena Japanese1347—
LMArena Korean1361—
LMArena Russian1387—
LMArena Spanish1411—

Instruction Following Not comparable

Grok 4.1 Fast: 72.8 (#127), Mercury 2.5: —

BenchmarkGrok 4.1 FastMercury 2.5
LMArena Instruction Following1376—

Long Context Not comparable

Grok 4.1 Fast: 42.4 (#121), Mercury 2.5: —

BenchmarkGrok 4.1 FastMercury 2.5
LMArena Longer Query1390—

Writing & Preference Not comparable

Grok 4.1 Fast: 57.4 (#126), Mercury 2.5: —

BenchmarkGrok 4.1 FastMercury 2.5
LMArena Text1408—
LMArena Creative Writing1394—
EQ-Bench Creative Writing1327—
LMArena Multi-Turn1389—

Frequently asked questions

Is Grok 4.1 Fast better than Mercury 2.5?

Grok 4.1 Fast has enough public results to be ranked (#131); Mercury 2.5 does not yet, so treat this comparison as directional.

Which is cheaper, Grok 4.1 Fast or Mercury 2.5?

Mercury 2.5 is cheaper. It lists at $0.04 per million input tokens and $0.15 per million output tokens; Grok 4.1 Fast lists at $0.20 and $0.50.

Which has the bigger context window?

Mercury 2.5 does, with 260K tokens against 128K.

How many benchmarks do Grok 4.1 Fast and Mercury 2.5 share?

2 benchmarks have published results for both models. Grok 4.1 Fast has 32 scored results on Noometry and Mercury 2.5 has 2.

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