Noometry

Model comparison

Claude Opus 5.5 vs Mercury 2.5

Claude Opus 5.5 is the stronger model overall, scoring 68.6 to 33.5 on the Noometry Index. Mercury 2.5 costs 119× less per token, which makes it the better buy when Claude Opus 5.5's lead doesn't matter for your workload.

Last verified . 4 shared benchmarks.

Claude Opus 5.5 Anthropic

68.6

Rank #3 Confirmed

Mercury 2.5 Inception

33.5

Rank #242 Reported

Summary

  • They share 4 benchmarks with published results for both. Claude Opus 5.5 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 Claude Opus 5.5 leads 91.8 to 23.3.
  • The biggest single-benchmark swing is ProofBench: 100% for Claude Opus 5.5 and 3% for Mercury 2.5.
  • Mercury 2.5 is cheaper at $0.04 / $0.15 per million input/output tokens, against $4 / $20 for Claude Opus 5.5.
  • Claude Opus 5.5 accepts more context: 1M tokens versus 260K.

Side by side

Claude Opus 5.5Mercury 2.5
ProviderAnthropicInception
Noometry Index68.633.5
Released2026-09-222026-09-08
WeightsProprietaryProprietary
Context window1M260K
Max output128K66K
Input $ / M tokens$4$0.04
Output $ / M tokens$20$0.15
Results tracked444

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Category by category

Coding Claude Opus 5.5 leads

Claude Opus 5.5: 71.9 (#3), Mercury 2.5: 39.5 (#156)

BenchmarkClaude Opus 5.5Mercury 2.5
SciCode66.9%38.5%
ALE-Bench2,147301.65
FrontierCode54.6%—
CursorBench57.8%—
LMArena WebDev1813—
FrontierSWE62.3%—
LMArena Coding1547—
MirrorCode77.4%—

Agentic & Tool Use Not comparable

Claude Opus 5.5: 45.3 (#15), Mercury 2.5: —

BenchmarkClaude Opus 5.5Mercury 2.5
APEX-Agents73.5%—
GDP.pdf30.6%—
Vending-Bench 29,235—

Reasoning Claude Opus 5.5 leads

Claude Opus 5.5: 80.2 (#3), Mercury 2.5: 22.4 (#193)

BenchmarkClaude Opus 5.5Mercury 2.5
CritPt31.7%0%
ARC-AGI-293.3%—
NYT Connections (extended)88.5%—
ARC-AGI-198.5%—
EBR-Bench71.4%—
LMArena Hard Prompts1535—
Mystery Game Puzzles71%—
DTBench98.9%—
LMCA68.2%—
Epoch Capabilities Index167.33—

Math Claude Opus 5.5 leads

Claude Opus 5.5: 91.8 (#3), Mercury 2.5: 23.3 (#272)

BenchmarkClaude Opus 5.5Mercury 2.5
ProofBench100%3%
FrontierMath (Tiers 1-3)91.2%—
FrontierMath Tier 495%—
OTIS Mock AIME 2024-2025100%—
LMArena Math1506—
FrontierMath Erdős2.9%—

Knowledge Not comparable

Claude Opus 5.5: 66.4 (#10), Mercury 2.5: —

BenchmarkClaude Opus 5.5Mercury 2.5
GPQA Diamond90.6%—
SimpleQA Verified72.2%—
LMArena Expert1547—

Multimodal Not comparable

Claude Opus 5.5: 57.8 (#1), Mercury 2.5: —

BenchmarkClaude Opus 5.5Mercury 2.5
LMArena Vision1321—
Blueprint-Bench 251.2%—
Furniture Assembly83.3%—

Multilingual Not comparable

Claude Opus 5.5: 59.1 (#2), Mercury 2.5: —

BenchmarkClaude Opus 5.5Mercury 2.5
LMArena Non-English1507—
LMArena Chinese1588—
LMArena French1514—
LMArena Russian1520—
LMArena Spanish1507—

Instruction Following Not comparable

Claude Opus 5.5: 80.0 (#3), Mercury 2.5: —

BenchmarkClaude Opus 5.5Mercury 2.5
LMArena Instruction Following1537—

Long Context Not comparable

Claude Opus 5.5: 47.1 (#19), Mercury 2.5: —

BenchmarkClaude Opus 5.5Mercury 2.5
LMArena Longer Query1532—

Writing & Preference Not comparable

Claude Opus 5.5: 78.2 (#3), Mercury 2.5: —

BenchmarkClaude Opus 5.5Mercury 2.5
LMArena Text1515—
LMArena Creative Writing1533—
EQ-Bench Creative Writing2050—
LMArena Multi-Turn1499—

Frequently asked questions

Is Claude Opus 5.5 better than Mercury 2.5?

Claude Opus 5.5 is the stronger model overall, scoring 68.6 to 33.5 on the Noometry Index. Mercury 2.5 costs 119× less per token, which makes it the better buy when Claude Opus 5.5's lead doesn't matter for your workload.

Which is cheaper, Claude Opus 5.5 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; Claude Opus 5.5 lists at $4 and $20.

Is Claude Opus 5.5 or Mercury 2.5 better for coding?

Claude Opus 5.5 scores higher on coding benchmarks: 71.9 versus 39.5 in the Noometry coding category.

Which has the bigger context window?

Claude Opus 5.5 does, with 1M tokens against 260K.

How many benchmarks do Claude Opus 5.5 and Mercury 2.5 share?

4 benchmarks have published results for both models. Claude Opus 5.5 has 44 scored results on Noometry and Mercury 2.5 has 4.

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