When weighing Claude Opus 5.5 vs Sonnet 5.5 for everyday office work, Sonnet 5.5 is enough for most jobs: it costs half as much per token, runs faster, and virtually ties Opus 5.5 on real-world work benchmarks like GDPval-AA. Choose Opus 5.5 for complex, open-ended judgment work and fact-heavy questions—and know that your effort setting changes the math.
Anthropic launched the two models six days apart during the fall 2026 wave of AI model releases: Claude Opus 5.5 arrived on September 22, 2026, and Claude Sonnet 5.5 followed on September 28. Most online comparisons focus on software engineering and terminal coding. Here, I’m looking at the question for everyone else—people using Claude in the app or through a team tool for writing, long documents, spreadsheets, slide decks, research, and light coding.
Claude Opus 5.5 vs Sonnet 5.5 at a glance
As of November 2026, Claude Opus 5.5 and Claude Sonnet 5.5 share the same 1-million-token context window, 128,000-token output limit, and June 2026 knowledge cutoff, while differing in per-token price, speed, thinking behavior, and who can access them in the Claude app.
| Feature | Claude Opus 5.5 | Claude Sonnet 5.5 |
|---|---|---|
| Release date | September 22, 2026 | September 28, 2026 |
| API ID | claude-opus-5-5 |
claude-sonnet-5-5 |
| Claude app availability | Paid plans (Pro, Max, Ultra, Team, Enterprise) | Free and paid plans (web, iOS, Android) |
| Comparative latency (Anthropic label) | Moderate | Fast |
| Fast mode (API & Claude Code) | Up to 2.5x faster ($8 / $40 per 1M tokens) | — |
| API input / output price (per 1M tokens) | $4 / $20 | $2 / $10 |
| Prompt cache read (per 1M tokens) | $0.20 | $0.10 |
| Batch API price (50% off, per 1M tokens) | $2 / $10 | $1 / $5 |
| Long-context surcharge | None | None |
| Context window | 1M tokens | 1M tokens |
| Max output | 128K tokens | 128K tokens |
| Adaptive thinking | Always on | On (can be turned off) |
| Default effort (Claude apps & Claude Code) | Medium | Medium |
| Default effort (Claude Platform API) | Medium | High |
| Reliable knowledge cutoff | June 2026 | June 2026 |
| Scheduled retirement | Not sooner than Sep 22, 2027 | Not sooner than Sep 28, 2027 |
Anthropic positions Opus 5.5 as the top model of the Claude 5.5 family, noting that it performs at the level of Claude Fable 5.1 on most work while costing 40% less to run than Opus 5 and generating output more than 30% faster than Opus 5. It also says Opus 5.5 is more resistant to prompt injection than Opus 5. Sonnet 5.5 is billed as a faster, lower-cost complement to Opus 5.5 that runs more than 30% faster than Sonnet 5 and costs up to 30% less per task than Sonnet 5.
Is Sonnet 5.5 as good as Opus 5.5?
On structured office and computer-use evaluations, Sonnet 5.5 performs nearly on par with Opus 5.5 when pushed to its highest effort settings, though Opus 5.5 holds a clear lead on hard multidisciplinary reasoning, factual recall without web search, and open-ended judgment.
To see where the two models separate, it helps to look at both Anthropic’s launch numbers and independent testing from Artificial Analysis (as of November 2026).
Work and reasoning benchmarks compared
First, here are the non-coding and knowledge-work benchmarks reported by Anthropic in its Sonnet 5.5 release post (comparing Sonnet 5.5 at its best effort against Opus 5.5 at Max or Xhigh effort):
| Benchmark (Anthropic-reported) | What it tests in plain English | Sonnet 5.5 | Opus 5.5 |
|---|---|---|---|
| GDPval-AA v2.1 (Elo) | Real-world work tasks across 44 occupations and 9 industries | 1844 | 1846 |
| AA-Briefcase v1.1 (Elo) | Long-horizon knowledge work | 1811 | 1822 |
| OSWorld 2.1 | Using a computer interface to complete tasks | 80.1% | 81.8% |
| Chartography (no tools) | Reading and interpreting charts | 61.6% | 64.4% |
| Humanity’s Last Exam (with tools) | Multidisciplinary hard academic and scientific reasoning | 64.5% | 67.7% |
(Note: Anthropic points out that Artificial Analysis ran GDPval-AA and AA-Briefcase on a pre-release build of Sonnet 5.5 that had a since-fixed structured-output bug, though the effect on scores was expected to be small. For context on how high both GDPval-AA scores are, Anthropic’s Opus 5.5 launch post noted that OpenAI’s GPT-6 Astra scored 1542 on the same evaluation.)
Next, here is how the two models compare when tested independently by Artificial Analysis with both models set to Max effort:
| Evaluation (Artificial Analysis, Max effort) | What it measures | Sonnet 5.5 (Max) | Opus 5.5 (Max) |
|---|---|---|---|
| AA Intelligence Index v5.0 | Composite score across 9 hard evaluations | 54 | 58 |
| AA-Briefcase v1.1 (Elo) | Long-horizon knowledge work | 1814 | 1801 |
| AutomationBench-AA | Automated business workflows | 72% | 70% |
| GDP.pdf | Working with PDF documents | 26% | 26% |
| AA-Omniscience v1.1 (net score) | Factual knowledge and not bluffing | 30 | 48 |
| HLE-Diamond | Hard multidisciplinary reasoning (no tools) | 53% | 68% |
If your work includes light coding alongside office tasks, the pattern is mixed: on Anthropic’s numbers, Opus 5.5 leads on CursorBench 4.0 (57.8% vs 55.5%) and FrontierCode 1.1 Main (54.4% vs 46.2% at Max, or 49.3% at Xhigh), while Sonnet 5.5 leads on agentic terminal coding in Terminal-Bench 4.0 (70.6% vs 66.4% for Opus at Xhigh). Artificial Analysis at Max effort similarly shows Sonnet ahead on Terminal-Bench 4.0 (64% vs 60%) and Opus ahead on FrontierCode 2.0 (46% vs 42%).
Where Sonnet ties—and where Opus pulls ahead
For day-to-day business work, the standout result is how close the two models are on applied office evaluations. On GDPval-AA v2.1, which tests real-world work across 44 occupations and 9 industries, the two models are essentially level (1844 vs 1846 Elo). On Artificial Analysis’s Max-effort runs, Sonnet 5.5 ties Opus 5.5 on working with PDF documents (GDP.pdf, 26% each) and edges slightly ahead on AA-Briefcase (1814 vs 1801) and business workflows (AutomationBench-AA, 72% vs 70%).
Where Opus 5.5 pulls away is on deep reasoning and raw factual knowledge:
- Hard reasoning: On HLE-Diamond (Artificial Analysis, Max effort), Opus 5.5 scores 68% to Sonnet’s 53%.
- Factual knowledge and hallucinations: On AA-Omniscience v1.1, which measures how much a model knows and whether it bluffs when it doesn’t know, Opus 5.5 at Max effort earns a net score of 48.1 (65.5% accuracy, with a 50.3% hallucination rate when it doesn’t know the answer) compared with 30.5 for Sonnet 5.5 at Max effort (51.5% accuracy, 43.3% hallucination rate). In plain terms, Sonnet bluffs slightly less often when stumped, but Opus knows substantially more facts in the first place.
- Sustained judgment: Anthropic itself cautions against reading the benchmark parity too broadly, stating in its Sonnet 5.5 announcement that “in our own testing, and in that of external testers, Opus 5.5 remains clearly stronger at complex, open-ended work requiring sustained judgment.”
Why effort level matters more than the model name
How much thinking effort you allow Claude to use often changes quality and cost per task more than switching between Opus 5.5 and Sonnet 5.5, as Anthropic’s own model documentation notes that tuning effort “is often a better lever than switching models.”
Both models use adaptive thinking—which is always on in Opus 5.5 and can be turned off in Sonnet 5.5—with five effort settings: Low, Medium, High, Xhigh, and Max. Lower effort settings respond faster and spend fewer thinking tokens, which suits routine work. Higher effort settings tell the model to reason longer and check its work more thoroughly.
I lined up Artificial Analysis’s per-effort numbers for both models (as of November 1, 2026) to see how quality, cost per task, and speed actually scale across all five levels:
| Effort setting | Sonnet 5.5 Index | Sonnet cost / task | Sonnet speed | Opus 5.5 Index | Opus cost / task | Opus speed |
|---|---|---|---|---|---|---|
| Low | 25 | $0.51 | 105.5 t/s | 35 | $0.98 | 77.6 t/s |
| Medium | 30 | $0.78 | 100.9 t/s | 48 | $2.45 | 79.6 t/s |
| High | 41 | $1.64 | 103.1 t/s | 52 | $3.46 | 79.6 t/s |
| Xhigh | 50 | $4.09 | 107.3 t/s | 57 | $6.05 | 85.4 t/s |
| Max | 54 | $10.02 | 139 t/s | 58 | $10.04 | 97 t/s |
(Source: Artificial Analysis per-effort model pages and comparison page, checked November 1, 2026. “Cost / task” is AA’s weighted average cost in USD across its Intelligence Index tasks. Note that Max speeds come from AA’s comparison page and were measured separately from the Low–Xhigh pages, so don’t compare Max token speeds directly against the other four rows.)
Looking across the rows reveals four practical takeaways that you won’t see in a simple price table:
- At the same effort level, Opus always scores higher and Sonnet is always faster. At Low through Xhigh effort, Sonnet generates tokens roughly 25% to 35% faster (about 101 to 107 tokens per second vs 78 to 85 tokens per second for Opus) and costs less per task at every level below Max.
- Opus at lower effort often matches or beats Sonnet at higher effort—for less money. Look at Sonnet 5.5 at Xhigh effort: it scores 50 on the Intelligence Index and costs $4.09 per task. Opus 5.5 at Medium effort gets nearly the same score (48) for $2.45 per task. Better yet, Opus 5.5 at High effort beats Sonnet Xhigh on quality (52 vs 50) while still costing less ($3.46 vs $4.09). Even at the bottom of the table, Opus Low (35 at $0.98) beats Sonnet Medium (30 at $0.78) for just $0.20 more per task.
- Default effort settings explain the “Opus 5.5 medium vs Sonnet 5.5 high” question. If you use the Claude Platform API without changing the effort parameter, Anthropic defaults Opus 5.5 to
mediumand Sonnet 5.5 tohigh. On Artificial Analysis’s suite, that default API pairing translates to an index score of 48 at $2.45 per task for Opus Medium versus 41 at $1.64 per task for Sonnet High. Inside the Claude apps and Claude Code, however, both models default to Medium—where the gap on AA’s hard tasks is wider (Opus Medium at 48 vs Sonnet Medium at 30). - Sonnet’s real sweet spot is Low to High effort. When a job doesn’t need top-tier reasoning scores, Sonnet at Low or Medium effort delivers the lowest absolute cost and fastest token speed. That matches Anthropic’s own guidance that Sonnet 5.5 “complements Opus 5.5 best when running at lower effort settings.”
One important caveat: Artificial Analysis’s Intelligence Index is built from 9 hard evaluations covering agentic coding, science, knowledge, and documents. Everyday office tasks—like drafting an email or summarizing a meeting transcript—are much easier and consume far fewer thinking tokens. In daily work, your actual dollar costs will be a fraction of these numbers, and both models will often succeed at default settings. Treat the table above as a relative signal of how effort scales, not a bill estimate for routine chat.
Is Opus 5.5 worth twice the price?
On a per-token basis, Opus 5.5 costs exactly twice as much as Sonnet 5.5 ($4/$20 vs $2/$10 per million input/output tokens as of November 2026), but whether a real task actually costs twice as much depends entirely on how many thinking tokens the model spends.
For straightforward work where neither model needs heavy multi-step reasoning, the 2x price ratio holds up cleanly. Take a concrete example calculated from Anthropic’s list prices:
- Summarizing a 20-page contract (13,500 input tokens + 1,500 output tokens, assuming no extra thinking tokens):
- Opus 5.5: (13,500 × $4 / 1M) + (1,500 × $20 / 1M) = $0.054 + $0.030 = $0.084
- Sonnet 5.5: (13,500 × $2 / 1M) + (1,500 × $10 / 1M) = $0.027 + $0.015 = $0.042
At four cents versus eight cents, both are cheap, and Sonnet cuts your API bill in half. The same 2x ratio applies if you use prompt caching ($0.20 vs $0.10 per million cached input tokens) or run overnight jobs through the Batch API ($2/$10 vs $1/$5 per million tokens). And unlike earlier generations, neither model charges a long-context surcharge across its 1-million-token window.
Where the 2x rule breaks down is at Max effort on hard problems. Because thinking tokens are billed as output tokens, a model that thinks longer runs up a larger tab. In Artificial Analysis’s Max-effort benchmark runs, Sonnet 5.5 generated roughly 65% more output tokens per task than Opus 5.5 (285K output tokens, including 206K reasoning tokens, compared with 173K output tokens and 120K reasoning tokens for Opus).
That extra token volume completely wiped out Sonnet’s 50% per-token discount:
- Average cost per task at Max effort (AA): $10.02 for Sonnet 5.5 vs $10.04 for Opus 5.5.
- Average total time per task at Max effort (AA): 1,298.5 seconds for Sonnet 5.5 vs 1,140.8 seconds for Opus 5.5—meaning Sonnet actually finished slower overall despite generating tokens faster (139 tokens/s vs 97 tokens/s).
As Anthropic itself puts it, Sonnet 5.5 costs less per task at lower effort settings, while “at higher settings, it can perform comparably at a similar cost.”
Everyday tasks where Sonnet 5.5 is enough
For well-scoped office work—drafting documents, building slide decks and spreadsheets from templates, summarizing files, reading charts, and running routine business workflows—Sonnet 5.5 delivers near-Opus results at a faster pace and lower cost (and, unlike Opus 5.5, it is available on the free Claude plan).
Based on Anthropic’s evaluations and Artificial Analysis’s benchmarks, here are the everyday tasks where Sonnet 5.5 is the practical choice:
- Polished slide decks, spreadsheets, and documents from a template: Anthropic specifically highlights Sonnet 5.5 for “creating polished documents, slides, and spreadsheets.” In an internal test reported in Anthropic’s Sonnet 5.5 launch post, when given a public company’s quarterly earnings materials, call transcripts, and a slide template, Sonnet 5.5 produced a 10-slide operating review whose first draft two experts judged ready to send as is. External testers also reported that it follows slide templates closely enough to make decks needing minimal editing.
- Routine writing, emails, and rewrites: Anthropic says both 5.5 models write more clearly than their predecessors. For standard memos, emails, and drafts with clear instructions, Sonnet 5.5 gives you fast turnaround.
- Working with PDFs and long documents: Both models share the same 1-million-token context window with no long-context surcharge, and they tied at 26% on Artificial Analysis’s GDP.pdf evaluation for working with PDF documents.
- Automated business workflows and data analysis: In Artificial Analysis’s testing, Sonnet 5.5 scored 72% on AutomationBench-AA (business workflows) compared with 70% for Opus 5.5, and Anthropic’s model selection guide recommends Sonnet 5.5 for everyday data analysis, content creation, and agentic tool use.
- Reading charts and visual interfaces: Sonnet 5.5 comes within a few percentage points of Opus 5.5 on Chartography without tools (61.6% vs 64.4%) and OSWorld 2.1 computer use (80.1% vs 81.8%).
- Everyday bug fixes and utility scripts: If your work involves fixing spreadsheet macros, small scripts, or routine bugs, Anthropic notes that Sonnet 5.5 is built for well-scoped tasks and fixing bugs, and it even outscored Opus 5.5 on Terminal-Bench 4.0.
When to pay for Opus 5.5
You should step up to Claude Opus 5.5 when a task is ambiguous, requires sustained judgment across many steps, depends on deep factual recall without web search, or involves complex multi-hour agent workflows.
Specifically, the data points to four situations where Opus 5.5 earns its keep:
- Ambiguous, open-ended strategy and analysis: When you don’t have a rigid template—say, stress-testing a business proposal, weighing conflicting contract clauses, or organizing a messy project from scratch—Anthropic notes that Opus 5.5 remains “clearly stronger at complex, open-ended work requiring sustained judgment.” Anthropic also notes that Opus 5.5 puts the most important information up front in its writing.
- Fact-heavy questions when web search isn’t available: On AA-Omniscience v1.1, Opus 5.5 answered 65.5% of factual questions accurately compared with 51.5% for Sonnet 5.5 (a net score of 48.1 vs 30.5). Neither model is immune to bluffing—Opus hallucinated on 50.3% of the questions it didn’t know, and Sonnet on 43.3%—so you should verify important claims either way, but Opus starts with a much deeper factual base.
- Hard multidisciplinary reasoning: On HLE-Diamond without tools (68% vs 53% on AA) and Humanity’s Last Exam with tools (67.7% vs 64.5% per Anthropic), Opus 5.5 holds a consistent margin on difficult scientific and analytical problems.
- Complex enterprise workflows and starting new API projects: In its model documentation, Anthropic states that “most workloads start with Claude Opus 5.5,” recommending it for multihour autonomous agents, large-scale refactoring, complex systems engineering, vision-heavy workflows, and computer use. It also offers stronger resistance to prompt injection than Opus 5.
Which one can you use in the Claude app?
In the Claude web and mobile apps, anyone can use Claude Sonnet 5.5 for free, whereas Claude Opus 5.5 requires a paid Pro, Max, Ultra, Team, or Enterprise subscription.
According to Anthropic’s product pages (as of November 2026), anyone can chat with Claude using Sonnet 5.5 on Claude.ai across web, iOS, and Android. If you are on the free tier, the decision is already made for you—and the good news from the benchmarks above is that you are getting a model that nearly matches Opus 5.5 on standard occupational work tasks (GDPval-AA).
If you pay for a Pro, Max, Ultra, Team, or Enterprise plan, you have access to both models in the app, with the default effort set to Medium.
What I’d actually do
If I were setting up a workflow for myself or a small team right now, I wouldn’t pay flagship rates for routine tasks—and I wouldn’t crank Sonnet up to Max effort to imitate Opus.
- Use Sonnet 5.5 at default (Medium) effort for most daily office work. For drafting, summarizing PDFs, turning notes into slides or spreadsheets, and routine analysis, Sonnet is faster, lighter on your usage quota or API bill, and practically tied with Opus on structured work evaluations.
- When Sonnet falls short, switch to Opus 5.5—don’t just push Sonnet to Xhigh or Max effort. This is the biggest takeaway from the Artificial Analysis effort data. On hard tasks, Opus 5.5 at Medium ($2.45/task, index 48) or High ($3.46/task, index 52) gave similar or better results than Sonnet 5.5 at Xhigh ($4.09/task, index 50) for less money. At Max effort, both cost ~$10 per task anyway.
- If you’re building on the API, test both ways. Anthropic’s docs suggest starting new workloads with Opus 5.5 to prove out what’s possible, then testing whether Sonnet 5.5 at Low or Medium effort can handle the job for a fraction of the cost. Our guide on how to choose an AI model walks through a 30-minute blind test you can run on your own documents before committing.
- Always fact-check ungrounded claims. Even Opus 5.5 bluffed on half of the questions it didn’t know on AA-Omniscience.
For more comparisons and practical breakdowns across providers, browse all of our AI models coverage.
FAQ
Is Claude Sonnet 5.5 free?
Yes. According to Anthropic, anyone can use Claude Sonnet 5.5 for free on Claude.ai across the web, iOS, and Android apps. Claude Opus 5.5 is not on the free tier; using Opus 5.5 in the Claude app requires a paid Pro, Max, Ultra, Team, or Enterprise plan.
Is Sonnet 5.5 cheaper than Opus 5.5?
Per token, yes: on the API as of November 2026, Sonnet 5.5 costs $2 per million input tokens and $10 per million output tokens, half of Opus 5.5’s $4 and $20 rates. Per task, Sonnet is cheaper than Opus at the same effort level from Low through Xhigh, but at Max effort on hard tasks, Artificial Analysis found both cost about $10 per task because Sonnet generates ~65% more output tokens.
Is Opus 5.5 better than Sonnet 5.5 for writing?
No public benchmark isolates prose quality, and Anthropic says both 5.5 models write more clearly than their predecessors, with Opus 5.5 putting the most important information up front. Anthropic recommends Sonnet 5.5 for well-scoped content creation and polished documents from templates, while noting that Opus 5.5 is clearly stronger for complex, open-ended work requiring sustained judgment.
Which is faster, Opus 5.5 or Sonnet 5.5?
Sonnet 5.5 is faster at generating tokens, labeled “Fast” by Anthropic versus “Moderate” for Opus 5.5, and clocked by Artificial Analysis at roughly 101–107 tokens per second across Low–Xhigh effort versus 78–85 for Opus. However, at Max effort, Sonnet spent so much longer reasoning that its average task took longer overall (1,298.5s vs 1,140.8s). Opus also offers a double-priced Fast mode (up to 2.5x faster).
Should I use Opus 5.5 medium or Sonnet 5.5 high?
Opus 5.5 at Medium effort and Sonnet 5.5 at High effort are the default settings on the Claude Platform API. On Artificial Analysis’s Intelligence Index (as of November 2026), Opus 5.5 Medium scores higher (48 vs 41) and costs about 50% more per task ($2.45 vs $1.64). Pick Sonnet High for routine speed and lower cost, or Opus Medium when accuracy on harder problems comes first.
Prices and benchmarks last checked November 1, 2026. Next review: November 30, 2026.
Sources
- Anthropic, Introducing Claude Opus 5.5, September 22, 2026
- Anthropic, Introducing Claude Sonnet 5.5, September 28, 2026
- Anthropic, Claude Opus product page and Claude Sonnet product page, accessed November 1, 2026
- Claude Platform Docs, Models overview, accessed November 1, 2026
- Claude Platform Docs, Choosing a model, accessed November 1, 2026
- Claude Platform Docs, Pricing, accessed November 1, 2026
- Artificial Analysis, Claude Opus 5.5 vs Claude Sonnet 5.5 and per-effort model pages (Opus Low, Medium, High, Xhigh; Sonnet Low, Medium, High, Xhigh), accessed November 1, 2026
- Artificial Analysis, AA-Omniscience Evaluation, accessed November 1, 2026
- Reuters, Anthropic rolls out second Claude 5.5 model, September 28, 2026
