Model comparison
Claude Sonnet 4.5 vs Mercury 2.5
Claude Sonnet 4.5 is the stronger model overall, scoring 44.1 to 33.5 on the Noometry Index. Mercury 2.5 costs 89× less per token, which makes it the better buy when Claude Sonnet 4.5's lead doesn't matter for your workload.
Last verified . 4 shared benchmarks.
Summary
- They share 4 benchmarks with published results for both. Claude Sonnet 4.5 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 Sonnet 4.5 leads 32.3 to 23.3.
- The biggest single-benchmark swing is ProofBench: 19% for Claude Sonnet 4.5 and 3% for Mercury 2.5.
- Mercury 2.5 is cheaper at $0.04 / $0.15 per million input/output tokens, against $3 / $15 for Claude Sonnet 4.5.
- Mercury 2.5 accepts more context: 260K tokens versus 200K.
Side by side
| Claude Sonnet 4.5 | Mercury 2.5 | |
|---|---|---|
| Provider | Anthropic | Inception |
| Noometry Index | 44.1 | 33.5 |
| Released | 2025-09-29 | 2026-09-08 |
| Weights | Proprietary | Proprietary |
| Context window | 200K | 260K |
| Max output | 64K | 66K |
| Input $ / M tokens | $3 | $0.04 |
| Output $ / M tokens | $15 | $0.15 |
| Results tracked | 73 | 4 |
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Category by category
Coding Claude Sonnet 4.5 leads
Claude Sonnet 4.5: 47.3 (#61), Mercury 2.5: 39.5 (#156)
| Benchmark | Claude Sonnet 4.5 | Mercury 2.5 |
|---|---|---|
| SciCode | 44.7% | 38.5% |
| ALE-Bench | 796.15 | 301.65 |
| SWE-bench Verified | 71.3% | — |
| SWE-bench Verified (bash only) | 71.4% | — |
| LMArena WebDev | 1393 | — |
| SWE-bench Multilingual | 67% | — |
| GSO | 14.7% | — |
| WeirdML | 47.7% | — |
| LMArena Coding | 1489 | — |
| AlgoTune | 1.52 | — |
Agentic & Tool Use Not comparable
Claude Sonnet 4.5: 38.3 (#32), Mercury 2.5: —
| Benchmark | Claude Sonnet 4.5 | Mercury 2.5 |
|---|---|---|
| Terminal-Bench | 46.5% | — |
| Berkeley Function Calling Leaderboard | 73.2% | — |
| GDPval | 42.5% | — |
| Remote Labor Index | 2.1% | — |
| τ²-bench Airline | 72% | — |
| τ²-bench Banking | 25.3% | — |
| τ²-bench Retail | 72.4% | — |
| τ²-bench Telecom | 84.9% | — |
| Cybench | 60% | — |
| DeepResearch Bench | 52.6% | — |
| OSWorld | 62.9% | — |
| LMArena Search | 1159 | — |
| METR Time Horizons | 67.4% | — |
| Vending-Bench 2 | 3,839 | — |
Reasoning Claude Sonnet 4.5 leads
Claude Sonnet 4.5: 26.9 (#125), Mercury 2.5: 22.4 (#193)
| Benchmark | Claude Sonnet 4.5 | Mercury 2.5 |
|---|---|---|
| CritPt | 1.1% | 0% |
| ARC-AGI-2 | 13.6% | — |
| SimpleBench | 54.3% | — |
| Kagi LLM Benchmark | 57.9% | — |
| NYT Connections (extended) | 37.3% | — |
| ARC-AGI-1 | 63.7% | — |
| Chess Puzzles | 12% | — |
| EnigmaEval | 6% | — |
| EBR-Bench | 2.4% | — |
| LMArena Hard Prompts | 1462 | — |
| Mystery Game Puzzles | 17% | — |
| DTBench | 83.2% | — |
| LMCA | 38.8% | — |
| Epoch Capabilities Index | 146.84 | — |
| ForecastBench | 61.9 | — |
Math Claude Sonnet 4.5 leads
Claude Sonnet 4.5: 32.3 (#216), Mercury 2.5: 23.3 (#272)
| Benchmark | Claude Sonnet 4.5 | Mercury 2.5 |
|---|---|---|
| ProofBench | 19% | 3% |
| FrontierMath (Tiers 1-3) | 23.9% | — |
| FrontierMath Tier 4 | 2.4% | — |
| OTIS Mock AIME 2024-2025 | 77.8% | — |
| Omni-MATH | 55.3% | — |
| LMArena Math | 1449 | — |
| MATH Level 5 | 97.7% | — |
| FrontierMath (Feb 2025 set) | 15.2% | — |
| FrontierMath Tier 4 (v1) | 4.2% | — |
Knowledge Not comparable
Claude Sonnet 4.5: 48.4 (#76), Mercury 2.5: —
| Benchmark | Claude Sonnet 4.5 | Mercury 2.5 |
|---|---|---|
| GPQA Diamond | 82.3% | — |
| Humanity's Last Exam | 13.7% | — |
| SimpleQA Verified | 30.7% | — |
| MMLU-Pro | 86.9% | — |
| Vectara Hallucination Rate | 12% | — |
| GPQA (HELM) | 68.6% | — |
| LMArena Expert | 1482 | — |
Multimodal Not comparable
Claude Sonnet 4.5: 34.8 (#89), Mercury 2.5: —
| Benchmark | Claude Sonnet 4.5 | Mercury 2.5 |
|---|---|---|
| VPCT | 39.8% | — |
| LMArena Document | 1450 | — |
Multilingual Not comparable
Claude Sonnet 4.5: 53.4 (#69), Mercury 2.5: —
| Benchmark | Claude Sonnet 4.5 | Mercury 2.5 |
|---|---|---|
| LMArena Non-English | 1425 | — |
| LMArena Chinese | 1459 | — |
| LMArena French | 1458 | — |
| LMArena German | 1427 | — |
| LMArena Japanese | 1390 | — |
| LMArena Korean | 1403 | — |
| LMArena Russian | 1437 | — |
| LMArena Spanish | 1457 | — |
Instruction Following Not comparable
Claude Sonnet 4.5: 75.0 (#78), Mercury 2.5: —
| Benchmark | Claude Sonnet 4.5 | Mercury 2.5 |
|---|---|---|
| IFEval | 85% | — |
| LMArena Instruction Following | 1459 | — |
Long Context Not comparable
Claude Sonnet 4.5: 45.2 (#46), Mercury 2.5: —
| Benchmark | Claude Sonnet 4.5 | Mercury 2.5 |
|---|---|---|
| LMArena Longer Query | 1476 | — |
Writing & Preference Not comparable
Claude Sonnet 4.5: 66.5 (#34), Mercury 2.5: —
| Benchmark | Claude Sonnet 4.5 | Mercury 2.5 |
|---|---|---|
| LMArena Text | 1439 | — |
| LMArena Creative Writing | 1442 | — |
| EQ-Bench Creative Writing | 1678 | — |
| WildBench | 85.4% | — |
| LMArena Multi-Turn | 1465 | — |
Frequently asked questions
Is Claude Sonnet 4.5 better than Mercury 2.5?
Claude Sonnet 4.5 is the stronger model overall, scoring 44.1 to 33.5 on the Noometry Index. Mercury 2.5 costs 89× less per token, which makes it the better buy when Claude Sonnet 4.5's lead doesn't matter for your workload.
Which is cheaper, Claude Sonnet 4.5 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 Sonnet 4.5 lists at $3 and $15.
Is Claude Sonnet 4.5 or Mercury 2.5 better for coding?
Claude Sonnet 4.5 scores higher on coding benchmarks: 47.3 versus 39.5 in the Noometry coding category.
Which has the bigger context window?
Mercury 2.5 does, with 260K tokens against 200K.
How many benchmarks do Claude Sonnet 4.5 and Mercury 2.5 share?
4 benchmarks have published results for both models. Claude Sonnet 4.5 has 73 scored results on Noometry and Mercury 2.5 has 4.