Claude Opus 5.5 vs Claude Sonnet 5.5: twice the price, is it worth it?
Claude Opus 5.5 costs $4 per million input tokens and $20 per million output tokens, exactly double Claude Sonnet 5.5's $2 and $10. Anthropic says Opus 5.5 is stronger on complex, open-ended work and Sonnet 5.5 is faster for well-scoped tasks. Anthropic's own table shows Opus ahead on most rows, mostly by a few points. Last verified 2026-10-27 (America/Chicago).
Evidence: Reported. Prices and specs are read from Anthropic's pages listed under Sources on 2026-10-27 (America/Chicago); benchmark figures are Anthropic's own or third-party mirrors, labeled as such. We have not run either model for this page.
Claude Opus 5.5 vs Claude Sonnet 5.5 at a glance
| Feature | Claude Opus 5.5 | Claude Sonnet 5.5 |
|---|---|---|
| Released | 2026-09-22 | 2026-09-28 (Anthropic launch post) |
| API model id | claude-opus-5-5 | claude-sonnet-5-5 |
| Input price, per 1M tokens | $4.00 | $2.00 |
| Output price, per 1M tokens | $20.00 | $10.00 |
| Cache read, per 1M tokens | $0.20 | $0.10 |
| Batch input / output, per 1M tokens | $2.00 / $10.00 | $1.00 / $5.00 |
| Fast mode, per 1M tokens (in / out) | $8 / $40 | Not listed |
| Anthropic's latency label | Moderate | Fast |
| Thinking, default effort | Adaptive (always on), default medium | Adaptive, default high |
| Context window / max output | 1M tokens / 128K tokens | 1M tokens / 128K tokens |
| Anthropic's one-line description | For long-running agentic coding and knowledge work | The best combination of speed and intelligence |
Both take text and image input and return text, with the same June 2026 knowledge cutoff, per Anthropic's models overview. Prices: Anthropic pricing. Full facts: Claude Opus 5.5 and Claude Sonnet 5.5.
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Cost of one example task
Illustration only, our arithmetic from list prices: one task with 200,000 uncached input tokens and 20,000 output tokens, with the same counts for both models. In practice token use differs by model and effort setting; Anthropic says Sonnet 5.5 typically needs far fewer tokens than Sonnet 5, which is a comparison with its own previous model, not with Opus.
| Model | List price per 1M tokens | Cost per task | Cost per 100 tasks |
|---|---|---|---|
| Claude Opus 5.5 | $4.00 in + $20.00 out | $1.20 | $120.00 |
| Claude Sonnet 5.5 | $2.00 in + $10.00 out | $0.60 | $60.00 |
At equal token counts, Opus 5.5 costs twice as much per task. Neither figure is a measured bill.
What the benchmark rows show
Anthropic's Sonnet 5.5 launch post (September 28, 2026) has a table of Anthropic's own evaluations. These are vendor figures, settings differ by row (Anthropic marks some entries with footnotes), and we did not reproduce them.
| Evaluation | Sonnet 5.5 | Opus 5.5 |
|---|---|---|
| Terminal-Bench 4.0 | 70.6% | 66.4% (footnoted by Anthropic) |
| FrontierCode 1.1 (Main) | 46.2% at Max effort | 54.4% |
| CursorBench 4.0 | 55.5% | 57.8% |
| GDPval-AA v2.1 | 1844 | 1846 |
| AA-Briefcase v1.1 | 1811 | 1822 |
| Humanity's Last Exam (with tools) | 64.5% | 67.7% |
| OSWorld 2.1 (partial) | 80.1% | 81.8% |
| Chartography (no tools) | 61.6% | 64.4% |
In that table Opus 5.5 is ahead on most rows by small margins, and Sonnet 5.5 is ahead on Terminal-Bench 4.0. Anthropic's own summary is that on several evaluations Sonnet 5.5 at Max effort performs comparably to Opus 5.5, but that in its testing and external testers' "Opus 5.5 remains clearly stronger at complex, open-ended work requiring sustained judgment." That is a vendor claim we did not verify.
| Source of the row | Claude Opus 5.5 | Claude Sonnet 5.5 |
|---|---|---|
| Official leaderboard mirror (Claude Code, max reasoning), snapshot 2026-10-25 | 64.85% | 61.82% |
| Vals AI (Vals-hosted table) | 65.15% | 64.14% |
| Artificial Analysis (its own harness) | 59.6% | 63.6% |
The third-party rows disagree on the order: Opus 5.5 leads in the first two and Sonnet 5.5 leads in Artificial Analysis's. We do not crown a winner from them; see Terminal-Bench 4.0 explained for why the scores depend on the harness. Source: BenchLM.
When to use Sonnet 5.5, when Opus 5.5
These rules are our reading of Anthropic's choosing-a-model guide, not test results. That guide says most workloads should start with Opus 5.5.
- Start with Opus 5.5 if you are unsure, or for multi-hour autonomous coding agents, large refactors, complex systems work, vision-heavy workflows and computer use, which Anthropic lists under Opus 5.5.
- Try Sonnet 5.5 first for code generation, data analysis, content creation, visual understanding and agentic tool use at lower cost, which Anthropic lists under Sonnet 5.5, and when speed matters.
- Check your own evals: Anthropic says tuning the effort setting is often a better lever than switching models. Sonnet 5.5 defaults to high effort and Opus 5.5 to medium.
- Cost is not only list price: the 2x gap is at equal tokens; measure tokens per task on your own work.
Who gets Opus 5.5 on Claude plans
Plan access changes; see our guide Claude Opus 5.5: free or paid? for what we read and when.
What we did not test
We did not call either API or run either model, so we have no measurements of speed, accuracy, token use or cost. Prices come from Anthropic's pages, benchmark rows from Anthropic's launch post and BenchLM's mirrors, all read on 2026-10-27.
FAQ
Is Opus 5.5 twice the price of Sonnet 5.5?
Yes at list price: Opus 5.5 is $4 input and $20 output per million tokens, Sonnet 5.5 is $2 and $10, per Anthropic's pricing page. Cache reads ($0.20 vs $0.10) and batch rates are also half for Sonnet. Actual cost per task depends on token use.
Is Opus 5.5 better than Sonnet 5.5?
Anthropic says Opus 5.5 is clearly stronger at complex, open-ended work needing sustained judgment, and its own table shows Opus ahead on most rows by small margins. Third-party Terminal-Bench 4.0 rows disagree on the order, so it depends on the task and harness.
Which Claude model does Anthropic recommend starting with?
Anthropic's models overview says to start with Claude Opus 5.5 for most workloads, use Fable 5.1 for demanding reasoning and long-horizon agentic work, and notes Sonnet 5.5 as the best combination of speed and intelligence.
Do Opus 5.5 and Sonnet 5.5 have the same context window?
Yes. Anthropic's models overview lists a 1M-token context window and 128K maximum output for both models, with text and image input and text output, and the same June 2026 knowledge cutoff.
Have you tested Opus 5.5 or Sonnet 5.5?
No. This page reports Anthropic's pages and third-party tables as read on 2026-10-27. We have not called either model or measured quality, speed or a real bill, so the cost example is arithmetic on list prices, not a measured cost.
Sources
- Anthropic: models overview (fetched 2026-10-27)
- Anthropic: pricing (fetched 2026-10-27)
- Anthropic: choosing a model (fetched 2026-10-27)
- Anthropic: Introducing Claude Sonnet 5.5 (fetched 2026-10-27)
- BenchLM: Terminal-Bench 4.0 (mirror of official, Vals and Artificial Analysis rows) (fetched 2026-10-27)
Related
Page history
- : First published from Anthropic's pricing, models and launch pages and BenchLM's Terminal-Bench 4.0 mirror, read on this date. Nothing was run.
Markdown version for agents: /compare/claude-opus-5-5-vs-claude-sonnet-5-5.md
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