Claude Opus 4.5 vs Claude Sonnet 5.5
| Spec | Claude Opus 4.5 | Claude Sonnet 5.5 |
|---|---|---|
| Respan Index | 39.8 (#60) | 73.1 (#2) |
| Blended price per 1M | $10 | $2 |
| Context window | 200K | 1M |
| Input / output per 1M | $5 / $25 | $1 / $5 |
| Max output | 64K | 128K |
| Input | text, vision | text, vision |
| Released | 2025-11-24 | 2026-09-28 |
Respan Index by category
Each category is scored 0 to 100, and how far ahead the winner is. Leads under a point are close to even.
| Category | Claude Opus 4.5 | Claude Sonnet 5.5 |
|---|---|---|
| Coding | 19.0 Claude Opus 4.5 | 79.6 Claude Sonnet 5.5 |
| Agents | 53.9 Claude Opus 4.5 | 78.4 Claude Sonnet 5.5 |
| Reasoning | 36.1 Claude Opus 4.5 | 79.0 Claude Sonnet 5.5 |
| Knowledge & language | 45.5 Claude Opus 4.5 | 48.5 Claude Sonnet 5.5 |
| Human preference | 53.2 Claude Opus 4.5 | 60.2 Claude Sonnet 5.5 |
Benchmarks both report
Claude Sonnet 5.5 leads on 19 of the 20 benchmarks both report. Higher is better. Each score links to where it was published.
| Benchmark | Claude Opus 4.5 | Claude Sonnet 5.5 |
|---|---|---|
| Chess Puzzles (Epoch AI) | 14% | 59% |
| LMArena Elo | 1474 | 1477 |
| LMArena WebDev (LMArena) | 1494 | 1770 |
| FrontierMath Tier 4 v2 (Epoch AI) | 4.9% | 80.5% |
| FrontierMath Tiers 1-3 v2 (Epoch AI) | 34.4% | 88.8% |
| Furniture Assembly (Epoch AI) | 28.3% | 75% |
| GPQA Diamond | 87% | 95.6% |
| LiveBench Agentic Coding (LiveBench) | 39.7% | 56.3% |
| LiveBench Coding (LiveBench) | 79.7% | 91.4% |
| LiveBench Data Analysis (LiveBench) | 74.4% | 78.6% |
| LiveBench Instruction Following (LiveBench) | 62.5% | 70.5% |
| LiveBench Language (LiveBench) | 81.3% | 83.4% |
| LiveBench Mathematics (LiveBench) | 90.4% | 96.7% |
| LiveBench Reasoning (LiveBench) | 80.1% | 91.6% |
| Mystery Game Puzzles (Epoch AI) | 22% | 65% |
| OTIS Mock AIME 2024-2025 (Epoch AI) | 86.1% | 100% |
| SAGE (Vals AI) | 52.1% | 51.8% |
| SimpleQA Verified | 45.7% | 46.5% |
| Vending-Bench 2 (Andon Labs) | 4967.06 | 11165.28 |
| SimpleBench (SimpleBench) | 62% | 75.9% |
FAQ
Is Claude Opus 4.5 better than Claude Sonnet 5.5?
Claude Sonnet 5.5 scores 73.1 on the Respan Index (#2), ahead of Claude Opus 4.5 at 39.8 (#60). Claude Sonnet 5.5 leads on 19 of the 20 benchmarks both report.
Which is cheaper, Claude Opus 4.5 or Claude Sonnet 5.5?
Claude Opus 4.5 lists at $5 input and $25 output per 1M tokens; Claude Sonnet 5.5 at $1 and $5. Claude Sonnet 5.5 is 5.0x cheaper per token at list price.
Which has the larger context window?
Claude Opus 4.5 accepts 200K tokens and Claude Sonnet 5.5 1M tokens.