Model comparison
Claude Sonnet 5.5 vs Mercury 2.5
Claude Sonnet 5.5 has enough public results to be ranked (#10); Mercury 2.5 does not yet, so treat this comparison as directional.
Last verified . 2 shared benchmarks.
Summary
- They share 2 benchmarks with published results for both. Claude Sonnet 5.5 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 Claude Sonnet 5.5 leads 88.7 to 22.4.
- The biggest single-benchmark swing is ProofBench: 100% for Claude Sonnet 5.5 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 5.5.
- Claude Sonnet 5.5 accepts more context: 1M tokens versus 260K.
Side by side
| Claude Sonnet 5.5 | Mercury 2.5 | |
|---|---|---|
| Provider | Anthropic | Inception |
| Noometry Index | 60.5 | 30.2 |
| Released | 2026-09-28 | 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 | 16 | 2 |
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Category by category
Coding Not comparable
Claude Sonnet 5.5: 65.5 (#6), Mercury 2.5: —
| Benchmark | Claude Sonnet 5.5 | Mercury 2.5 |
|---|---|---|
| ALE-Bench | 1,819 | 301.65 |
| FrontierCode | 52.1% | — |
| CursorBench | 55.5% | — |
| LMArena WebDev | 1699 | — |
| FrontierSWE | 61.9% | — |
| SciCode | 61% | — |
Agentic & Tool Use Not comparable
Claude Sonnet 5.5: 44.9 (#14), Mercury 2.5: —
| Benchmark | Claude Sonnet 5.5 | Mercury 2.5 |
|---|---|---|
| APEX-Agents | 75.5% | — |
Reasoning Not comparable
Claude Sonnet 5.5: 52.4 (#29), Mercury 2.5: —
| Benchmark | Claude Sonnet 5.5 | Mercury 2.5 |
|---|---|---|
| CritPt | 31.4% | — |
| Mystery Game Puzzles | 65% | — |
Math Claude Sonnet 5.5 leads
Claude Sonnet 5.5: 88.7 (#4), Mercury 2.5: 22.4
| Benchmark | Claude Sonnet 5.5 | Mercury 2.5 |
|---|---|---|
| ProofBench | 100% | 3% |
| FrontierMath (Tiers 1-3) | 88.8% | — |
| FrontierMath Tier 4 | 80.5% | — |
| OTIS Mock AIME 2024-2025 | 100% | — |
Knowledge Not comparable
Claude Sonnet 5.5: 66.0 (#11), Mercury 2.5: —
| Benchmark | Claude Sonnet 5.5 | Mercury 2.5 |
|---|---|---|
| GPQA Diamond | 95.6% | — |
| SimpleQA Verified | 46.5% | — |
Multimodal Not comparable
Claude Sonnet 5.5: 53.2 (#5), Mercury 2.5: —
| Benchmark | Claude Sonnet 5.5 | Mercury 2.5 |
|---|---|---|
| Furniture Assembly | 75% | — |
Frequently asked questions
Is Claude Sonnet 5.5 better than Mercury 2.5?
Claude Sonnet 5.5 has enough public results to be ranked (#10); Mercury 2.5 does not yet, so treat this comparison as directional.
Which is cheaper, Claude Sonnet 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 Sonnet 5.5 lists at $2 and $10.
Which has the bigger context window?
Claude Sonnet 5.5 does, with 1M tokens against 260K.
How many benchmarks do Claude Sonnet 5.5 and Mercury 2.5 share?
2 benchmarks have published results for both models. Claude Sonnet 5.5 has 16 scored results on Noometry and Mercury 2.5 has 2.