Claude Sonnet 5.5 vs Opus 5.5 vs GPT-6 Sol: which one should a small business use?

The short answer: try Claude Sonnet 5.5 first for coding, document work and everyday agent tasks. It costs half as much per token as Claude Opus 5.5, and Anthropic reports it ahead on one coding test and about level on knowledge work. Move up to Opus 5.5 for the hardest open-ended work, where Anthropic says Opus stays clearly stronger. Sonnet 5.5 is also much wordier than GPT-6 Sol, so it does not always cost less per finished job, even at the same list price. Test your own task and compare real bills.

Every number below comes from Anthropic, from OpenAI or from Artificial Analysis, an independent benchmark site, and is labelled with who measured it. Checked on 29 September 2026. Prices are list prices per 1 million tokens on each lab's own API.

Update, 1 October 2026: OpenAI released GPT-6.1 Sol on 29 September at the same $2 / $10 as GPT-6 Sol. Artificial Analysis (independent) scores it 52, up from 48, at about $0.72 per task, so wherever this page recommends GPT-6 Sol, GPT-6.1 Sol is now the better pick at the same price. Our best AI model for coding guide adds it, with independent LiveBench scores for Sonnet 5.5 and Opus 5.5.

The three models side by side

The last three index rows are from Artificial Analysis pages for Sonnet 5.5, Opus 5.5 and GPT-6 Sol, read on 29 September 2026, at each model's highest effort setting. The site lists more models each week, so rankings move; the scores and costs above are what it printed that day.

What Anthropic reports

These are Anthropic's own figures, not independent tests.

So Sonnet 5.5 wins one coding test and trails on two, and is within two points of Opus 5.5 on knowledge work. Against its own predecessor the change is large: Anthropic reports Sonnet 5 at 10.3% on Terminal-Bench 4.0, says Sonnet 5.5 generates output more than 30% faster, and says it costs up to 30% less per task than Sonnet 5.

Anthropic's own advice on choosing: "Where Opus 5.5 is built for complex work requiring careful judgment, Sonnet 5.5 is strongest at well-scoped everyday tasks, fixing bugs, and creating polished documents, slides, and spreadsheets." It also says Opus 5.5 "remains clearly stronger at complex, open-ended work requiring sustained judgment". Source.

OpenAI's GPT-6 Sol figures were published against older Claude models, and no lab has published a head-to-head of Sonnet 5.5 against Sol, so the independent index is the only place all three share a scale.

A cheaper rate card is not always a cheaper job

Sonnet 5.5 and GPT-6 Sol have the same list price, $2 / $10. On Artificial Analysis's index run, though, Sonnet 5.5 wrote about 410 million output tokens and Sol wrote 77 million, and the site labels Sonnet 5.5 "very verbose". The average cost per task came out at $7.60 for Sonnet 5.5 and $1.05 for Sol. Opus 5.5 costs twice as much per token as Sonnet 5.5 but wrote fewer tokens, and its average was $5.98.

Two cautions before you read too much into that:

• Artificial Analysis ran every model at its highest effort. Claude Code and the Claude apps default to medium effort, and the Claude API defaults to high, so a real bill will differ from these averages.
• Sol scores 48 on the index against Sonnet 5.5's 56. The cheaper job is also the less capable one on this measure.

The practical lesson is to compare what a whole job costs on your own work, not the price per token.

Which one for which job

Example, not a quote: 1,000 customer replies, each with 2,000 tokens of input and 500 tokens of output, at list price and without caching, cost about $9 on Sonnet 5.5, $9 on Sol and $18 on Opus 5.5. Reasoning tokens are billed as output, so a model that thinks longer costs more than this, which is exactly the Sonnet 5.5 caveat above.

Things to check before you switch

1. Set the effort level on purpose. Sonnet 5.5 has five settings, from low to max. Anthropic says lower settings answer faster and use fewer tokens, and higher ones reason longer. Start at the default and only raise it if a real task fails.
2. Risky security work falls back to the older model. Anthropic says routine bug finding and fixing works, but higher-risk cybersecurity tasks visibly fall back to Sonnet 5. If your work is security research, read the launch post first.
3. Haiku 5.5 is not out yet. Anthropic says it joins the family "in the coming weeks". For now the small, fast Claude is still Haiku 4.5 at $1 / $5, so do not plan around a Haiku 5.5 price that does not exist.
4. Switching is a one-line change. The model id is claude-sonnet-5-5. Sonnet 5 costs the same $2 / $10 and stays available as a legacy model, so there is no price reason to stay on it.
5. The 272K rule on OpenAI. A GPT-6 Sol prompt over 272K input tokens is billed at twice the input rate and 1.5 times the output rate for the whole request. Anthropic bills the full 1M window at the standard rate for both Claude models.

Our model tracker keeps the current pick per category, with sources. If you want a stack chosen for your own workflow rather than a general ranking, that is what a Business AI Plan does. The free 2-minute AI plan finder is the quick first step.

Frequently asked questions

How much does Claude Sonnet 5.5 cost? $2 per 1M input tokens and $10 per 1M output tokens, the same as Sonnet 5. Cache reads are $0.20 per 1M and 5-minute cache writes $2.50. The Batch API is half price at $1 / $5.

Is Claude Sonnet 5.5 better than Opus 5.5? Not overall. Artificial Analysis scores Sonnet 5.5 at 56 and Opus 5.5 at 58. Anthropic reports Sonnet 5.5 ahead on Terminal-Bench 4.0 but behind on CursorBench 4.0, and says Opus 5.5 is clearly stronger at complex, open-ended work.

Is Sonnet 5.5 the same price as GPT-6 Sol? Yes, $2 / $10 per 1M tokens. Cost per finished job can differ a lot, because Sonnet 5.5 wrote far more output tokens than Sol on Artificial Analysis's run.

When was Claude Sonnet 5.5 released? On 28 September 2026, on the Claude API, in the Claude apps and Claude Code, and on Amazon Web Services, Google Cloud and Microsoft Azure.

Has Claude Haiku 5.5 been released? No. Anthropic says it is coming in the coming weeks. Claude Haiku 4.5 is still the current Haiku.

Can I run Claude Sonnet 5.5 on my own server? No. It is a closed-weights, cloud-only model. If data has to stay in-house, use an open-weights model such as DeepSeek V4.1 Flash.

Sources: Anthropic — Claude Sonnet 5.5, Anthropic — Claude Opus 5.5, Anthropic — models overview, Anthropic API pricing, OpenAI — GPT-6 Sol model page, OpenAI API pricing, Artificial Analysis — Claude Sonnet 5.5, Artificial Analysis — Claude Opus 5.5, Artificial Analysis — GPT-6 Sol. Checked 29 September 2026.