Model comparison
Claude Sonnet 5 vs Mercury 2.5
Claude Sonnet 5 is the stronger model overall, scoring 54.6 to 33.5 on the Noometry Index. Mercury 2.5 costs 59× less per token, which makes it the better buy when Claude Sonnet 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 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 5 leads 66.2 to 23.3.
- The biggest single-benchmark swing is ProofBench: 77% for Claude Sonnet 5 and 3% for Mercury 2.5.
- Mercury 2.5 is cheaper at $0.04 / $0.15 per million input/output tokens, against $2 / $10 for Claude Sonnet 5.
- Claude Sonnet 5 accepts more context: 1M tokens versus 260K.
Side by side
| Claude Sonnet 5 | Mercury 2.5 | |
|---|---|---|
| Provider | Anthropic | Inception |
| Noometry Index | 54.6 | 33.5 |
| Released | 2026-06-29 | 2026-09-08 |
| Weights | Proprietary | Proprietary |
| Context window | 1M | 260K |
| Max output | 128K | 66K |
| Input $ / M tokens | $2 | $0.04 |
| Output $ / M tokens | $10 | $0.15 |
| Results tracked | 51 | 4 |
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Category by category
Coding Claude Sonnet 5 leads
Claude Sonnet 5: 55.5 (#26), Mercury 2.5: 39.5 (#156)
| Benchmark | Claude Sonnet 5 | Mercury 2.5 |
|---|---|---|
| SciCode | 54.3% | 38.5% |
| ALE-Bench | 1,463 | 301.65 |
| DeepSWE | 53.8% | — |
| FrontierCode | 42.7% | — |
| CursorBench | 34.1% | — |
| LMArena WebDev | 1541 | — |
| GSO | 37.3% | — |
| WeirdML | 68.8% | — |
| LMArena Coding | 1483 | — |
Agentic & Tool Use Not comparable
Claude Sonnet 5: 42.8 (#18), Mercury 2.5: —
| Benchmark | Claude Sonnet 5 | Mercury 2.5 |
|---|---|---|
| APEX-Agents | 54.5% | — |
| GBAEval | 65.3% | — |
| LMArena Search | 1194 | — |
| Vending-Bench 2 | 6,378 | — |
Reasoning Claude Sonnet 5 leads
Claude Sonnet 5: 49.1 (#39), Mercury 2.5: 22.4 (#193)
| Benchmark | Claude Sonnet 5 | Mercury 2.5 |
|---|---|---|
| CritPt | 16.9% | 0% |
| SimpleBench | 60.6% | — |
| NYT Connections (extended) | 75.1% | — |
| Chess Puzzles | 35% | — |
| LMArena Hard Prompts | 1461 | — |
| Mystery Game Puzzles | 35% | — |
| DTBench | 92.5% | — |
| LMCA | 50% | — |
| Surface Evolver Bench | 60% | — |
| Bench to the Future 3 | 0.14 | — |
| Epoch Capabilities Index | 156.21 | — |
| ForecastBench | 61.1 | — |
Math Claude Sonnet 5 leads
Claude Sonnet 5: 66.2 (#27), Mercury 2.5: 23.3 (#272)
| Benchmark | Claude Sonnet 5 | Mercury 2.5 |
|---|---|---|
| ProofBench | 77% | 3% |
| FrontierMath (Tiers 1-3) | 65.6% | — |
| FrontierMath Tier 4 | 29.3% | — |
| OTIS Mock AIME 2024-2025 | 94.7% | — |
| LMArena Math | 1467 | — |
Knowledge Not comparable
Claude Sonnet 5: 55.6 (#47), Mercury 2.5: —
| Benchmark | Claude Sonnet 5 | Mercury 2.5 |
|---|---|---|
| GPQA Diamond | 90.5% | — |
| SimpleQA Verified | 33.7% | — |
| LMArena Expert | 1490 | — |
Multimodal Not comparable
Claude Sonnet 5: 42.4 (#31), Mercury 2.5: —
| Benchmark | Claude Sonnet 5 | Mercury 2.5 |
|---|---|---|
| LMArena Vision | 1274 | — |
| Blueprint-Bench 2 | 24.9% | — |
| LMArena Document | 1466 | — |
Multilingual Not comparable
Claude Sonnet 5: 53.8 (#55), Mercury 2.5: —
| Benchmark | Claude Sonnet 5 | Mercury 2.5 |
|---|---|---|
| LMArena Non-English | 1431 | — |
| LMArena Chinese | 1477 | — |
| LMArena French | 1460 | — |
| LMArena German | 1440 | — |
| LMArena Japanese | 1422 | — |
| LMArena Korean | 1411 | — |
| LMArena Russian | 1451 | — |
| LMArena Spanish | 1437 | — |
Instruction Following Not comparable
Claude Sonnet 5: 76.3 (#41), Mercury 2.5: —
| Benchmark | Claude Sonnet 5 | Mercury 2.5 |
|---|---|---|
| LMArena Instruction Following | 1452 | — |
Long Context Not comparable
Claude Sonnet 5: 44.8 (#55), Mercury 2.5: —
| Benchmark | Claude Sonnet 5 | Mercury 2.5 |
|---|---|---|
| LMArena Longer Query | 1463 | — |
Writing & Preference Not comparable
Claude Sonnet 5: 69.2 (#25), Mercury 2.5: —
| Benchmark | Claude Sonnet 5 | Mercury 2.5 |
|---|---|---|
| LMArena Text | 1442 | — |
| LMArena Creative Writing | 1416 | — |
| EQ-Bench Creative Writing | 1794 | — |
| EQ-Bench 4 | 1236 | — |
| LMArena Multi-Turn | 1454 | — |
Frequently asked questions
Is Claude Sonnet 5 better than Mercury 2.5?
Claude Sonnet 5 is the stronger model overall, scoring 54.6 to 33.5 on the Noometry Index. Mercury 2.5 costs 59× less per token, which makes it the better buy when Claude Sonnet 5's lead doesn't matter for your workload.
Which is cheaper, Claude Sonnet 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 5 lists at $2 and $10.
Is Claude Sonnet 5 or Mercury 2.5 better for coding?
Claude Sonnet 5 scores higher on coding benchmarks: 55.5 versus 39.5 in the Noometry coding category.
Which has the bigger context window?
Claude Sonnet 5 does, with 1M tokens against 260K.
How many benchmarks do Claude Sonnet 5 and Mercury 2.5 share?
4 benchmarks have published results for both models. Claude Sonnet 5 has 51 scored results on Noometry and Mercury 2.5 has 4.