Claude Opus 5.5 vs Claude Sonnet 5.5.
Verdict by category, tale of the tape, shared benchmarks only, and cost at three workloads — all from the tracked data.
Verdict by category
| Category | Claude Opus 5.5 | Claude Sonnet 5.5 | Winner |
|---|---|---|---|
| League Score | 96.4 | 86.9 | Claude Opus 5.5 |
| Coding (SWE-bench %) | — | — | — |
| Reasoning (GPQA %) | — | — | — |
| Context (tokens) | 1000000 | 1000000 | Draw |
| Speed (tok/s) | 75.6 | — | — |
| Price (blended $/1M) | $8.00 | $4.00 | Claude Sonnet 5.5 (cheaper) |
Tale of the tape
| Spec | Claude Opus 5.5 | Claude Sonnet 5.5 |
|---|---|---|
| Maker | Anthropic | Anthropic |
| Released | Sep 22, 2026 | Sep 28, 2026 |
| League Score | 96 | 87 |
| Context | 1,000,000 tokens | 1,000,000 tokens |
| Max output | 128,000 | 128,000 |
| $/1M input | $4.00 | $2.00 |
| $/1M output | $20.00 | $10.00 |
| Weights | Closed | Closed |
| Speed | 75.6 t/s | — |
Head-to-head benchmarks (shared only)
| Benchmark | Claude Opus 5.5 | Claude Sonnet 5.5 |
|---|---|---|
| LiveBench overall | 86.5 | 82.5 |
Cost at three workloads
| Workload | Claude Opus 5.5 | Claude Sonnet 5.5 |
|---|---|---|
| Light — 1M in / 250K out | $9.00 | $4.50 |
| Standard — 10M in / 2.5M out | $90.00 | $45.00 |
| Long-context — 50M in / 5M out | $300.00 | $150.00 |
The pick
Pick Claude Opus 5.5 if you want the higher overall League Score.
Pick Claude Sonnet 5.5 if you want the lower running cost.
All figures from the model database — sources and dates on each model page. Cost your own workload or compare a different pair.
Frequently asked questions
Which is better overall, Claude Opus 5.5 or Claude Sonnet 5.5?
Claude Opus 5.5 leads on overall League Score, 96 to 87 — a gap of 10 points on a composite of sourced benchmarks. That is overall form, not every category: check the per-category verdicts before choosing.
Which is cheaper, Claude Opus 5.5 or Claude Sonnet 5.5?
Claude Sonnet 5.5 is cheaper: $4.00 vs $8.00 blended per 1M tokens (3:1 input/output mix) — about 2.0x less per token.
Which has the bigger context window, Claude Opus 5.5 or Claude Sonnet 5.5?
Neither — both take 1M of context.
Are Claude Opus 5.5 and Claude Sonnet 5.5 open source?
Claude Opus 5.5 is closed weights — API access only; Claude Sonnet 5.5 is closed weights — API access only.