Noometry

Model comparison

DeepSeek V4.1 Flash vs Mercury 2.5

DeepSeek V4.1 Flash is the stronger model overall, scoring 52.8 to 33.5 on the Noometry Index. Mercury 2.5 costs 3.9× less per token, which makes it the better buy when DeepSeek V4.1 Flash's lead doesn't matter for your workload.

Last verified . 4 shared benchmarks.

DeepSeek V4.1 Flash DeepSeek

52.8

Rank #38 Confirmed

Mercury 2.5 Inception

33.5

Rank #242 Reported

Summary

  • They share 4 benchmarks with published results for both. DeepSeek V4.1 Flash scores higher in 3 categories and Mercury 2.5 in 0 categories; 3 gaps are clear of the uncertainty.
  • The widest gap is in math, where DeepSeek V4.1 Flash leads 66.7 to 23.3.
  • The biggest single-benchmark swing is ProofBench: 54% for DeepSeek V4.1 Flash and 3% for Mercury 2.5.
  • Mercury 2.5 is cheaper at $0.04 / $0.15 per million input/output tokens, against $0.15 / $0.60 for DeepSeek V4.1 Flash.
  • DeepSeek V4.1 Flash accepts more context: 1M tokens versus 260K.
  • DeepSeek V4.1 Flash has downloadable open weights; the other is API-only.

Side by side

DeepSeek V4.1 FlashMercury 2.5
ProviderDeepSeekInception
Noometry Index52.833.5
Released2026-09-092026-09-08
WeightsOpenProprietary
Context window1M260K
Max output393K66K
Input $ / M tokens$0.15$0.04
Output $ / M tokens$0.60$0.15
Results tracked374

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Category by category

Coding DeepSeek V4.1 Flash leads

DeepSeek V4.1 Flash: 52.9 (#32), Mercury 2.5: 39.5 (#156)

BenchmarkDeepSeek V4.1 FlashMercury 2.5
SciCode51.9%38.5%
ALE-Bench1,092301.65
LMArena WebDev1619—
LMArena Coding1506—

Agentic & Tool Use Not comparable

DeepSeek V4.1 Flash: 31.2 (#69), Mercury 2.5: —

BenchmarkDeepSeek V4.1 FlashMercury 2.5
APEX-Agents39.5%—
GDP.pdf19.8%—

Reasoning DeepSeek V4.1 Flash leads

DeepSeek V4.1 Flash: 50.2 (#36), Mercury 2.5: 22.4 (#193)

BenchmarkDeepSeek V4.1 FlashMercury 2.5
CritPt14.3%0%
NYT Connections (extended)89.6%—
LMArena Hard Prompts1483—
Mystery Game Puzzles43%—
DTBench89.9%—
LMCA47%—
Surface Evolver Bench46.3%—
Epoch Capabilities Index154.9—

Math DeepSeek V4.1 Flash leads

DeepSeek V4.1 Flash: 66.7 (#25), Mercury 2.5: 23.3 (#272)

BenchmarkDeepSeek V4.1 FlashMercury 2.5
ProofBench54%3%
FrontierMath (Tiers 1-3)67.4%—
FrontierMath Tier 426.8%—
OTIS Mock AIME 2024-202598.3%—
LMArena Math1477—

Knowledge Not comparable

DeepSeek V4.1 Flash: 57.9 (#38), Mercury 2.5: —

BenchmarkDeepSeek V4.1 FlashMercury 2.5
GPQA Diamond89.8%—
LMArena Expert1506—

Multimodal Not comparable

DeepSeek V4.1 Flash: 39.1 (#61), Mercury 2.5: —

BenchmarkDeepSeek V4.1 FlashMercury 2.5
LMArena Vision1277—
Furniture Assembly34.2%—

Multilingual Not comparable

DeepSeek V4.1 Flash: 55.0 (#35), Mercury 2.5: —

BenchmarkDeepSeek V4.1 FlashMercury 2.5
LMArena Non-English1448—
LMArena Chinese1497—
LMArena French1452—
LMArena German1484—
LMArena Japanese1412—
LMArena Korean1452—
LMArena Russian1471—
LMArena Spanish1459—

Instruction Following Not comparable

DeepSeek V4.1 Flash: 77.3 (#26), Mercury 2.5: —

BenchmarkDeepSeek V4.1 FlashMercury 2.5
LMArena Instruction Following1474—

Long Context Not comparable

DeepSeek V4.1 Flash: 45.2 (#47), Mercury 2.5: —

BenchmarkDeepSeek V4.1 FlashMercury 2.5
LMArena Longer Query1475—

Writing & Preference Not comparable

DeepSeek V4.1 Flash: 65.4 (#48), Mercury 2.5: —

BenchmarkDeepSeek V4.1 FlashMercury 2.5
LMArena Text1462—
LMArena Creative Writing1435—
EQ-Bench Creative Writing1540—
LMArena Multi-Turn1457—

Frequently asked questions

Is DeepSeek V4.1 Flash better than Mercury 2.5?

DeepSeek V4.1 Flash is the stronger model overall, scoring 52.8 to 33.5 on the Noometry Index. Mercury 2.5 costs 3.9× less per token, which makes it the better buy when DeepSeek V4.1 Flash's lead doesn't matter for your workload.

Which is cheaper, DeepSeek V4.1 Flash 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; DeepSeek V4.1 Flash lists at $0.15 and $0.60.

Is DeepSeek V4.1 Flash or Mercury 2.5 better for coding?

DeepSeek V4.1 Flash scores higher on coding benchmarks: 52.9 versus 39.5 in the Noometry coding category.

Which has the bigger context window?

DeepSeek V4.1 Flash does, with 1M tokens against 260K.

How many benchmarks do DeepSeek V4.1 Flash and Mercury 2.5 share?

4 benchmarks have published results for both models. DeepSeek V4.1 Flash has 37 scored results on Noometry and Mercury 2.5 has 4.

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