Claude Sonnet 5.5 vs Gemini 3.8 Flash
Claude Sonnet 5.5 and Gemini 3.8 Flash are within three points on the Models at Work leaderboard, which we treat as a tie (66 vs 65 out of 100). On independent tests alone, Claude Sonnet 5.5 is ahead (68 vs 63). Gemini 3.8 Flash is cheaper: 1,000 support replies cost about $3.75 at list price, against $10 on Claude Sonnet 5.5, which is 2.7 times as much. On the Artificial Analysis Intelligence Index, one of the independent tests, Claude Sonnet 5.5 leads 55 to 31.
| Claude Sonnet 5.5 · Anthropic | Gemini 3.8 Flash · Google | |
|---|---|---|
| Leaderboard rank | #10 | #12 |
| Score (0–100) | 66 | 65 |
| Kind of work | Everyday default | High-volume work |
| Price per 1M tokens | $2 to read · $10 to write | $0.75 to read · $3.75 to write |
| Reads at once | 1M tokens (about 750,000 words) | 1M tokens (about 750,000 words) |
| Where you can get it | Claude Team and Enterprise, Amazon Bedrock, Gemini Enterprise Agent Platform (Google Cloud), Microsoft Foundry, Microsoft 365 Copilot, GitHub Copilot | Gemini Enterprise Agent Platform (Google Cloud), Gemini app (Google AI Pro and Ultra) |
| Can a company host it itself | No | No |
| Artificial Analysis Intelligence Index | 55 | 31 |
| Humanity's Last Exam, Diamond (Scale) | 37.50 | 34.30 |
| Arena Text score | Not measured | 1497 (rank 8) |
| Scale SWE-Bench Pro V2 (mini-swe-agent) | Not measured | 58.80% |
| Humanity's Sixth Sense (Scale) | Not measured | 41.60 |
| Best for | Support replies at volume, Drafting proposals and reports, Summarising meetings and long documents, Answering questions from company documents | First-pass support replies, Summarising documents, images and recordings at volume, Routine multi-step tasks on a budget |
Cost of 1,000 jobs
| 1,000 of these | Claude Sonnet 5.5 | Gemini 3.8 Flash |
|---|---|---|
| Support repliesthe customer message, the account notes and two help articles read; a 300-word reply written | $10 | $3.75 |
| Documents processeda two-page invoice or form read; the fields pulled out | $7 | $2.63 |
| Calls summariseda 40-minute call transcript read; a summary and next steps written | $26 | $9.75 |
| Contracts revieweda 40-page contract read against a checklist; a memo of issues written | $75 | $28 |
| Drafts writtena brief and one example read; a 600-word email or proposal section written | $11 | $4.13 |
Worked out from each vendor’s list price and a fixed size for each job. A product built on a model charges its own price on top. See what every model costs for the same jobs.
Choose Claude Sonnet 5.5 for
- Support replies at volume
- Drafting proposals and reports
- Summarising meetings and long documents
- Answering questions from company documents
A sound everyday default: 55 on Artificial Analysis's index, four points behind Claude Opus 5.5, at half its list price.
Caveats: The saving depends on the effort setting: at the top setting Artificial Analysis's test run cost $10.02 per task, level with Opus 5.5 ($10.04). On Scale's Humanity's Last Exam, a set of expert-level questions, it scores 37.5 against 55.0 for Opus 5.5: move up for the hardest analysis. In Microsoft 365 Copilot, Claude models are on by default for most commercial customers but off in the EU, EFTA and UK until an administrator allows Anthropic as a subprocessor (a company permitted to handle your data), per Microsoft Learn. In Microsoft 365 Copilot it has been rolling out in phases across Word, Excel, PowerPoint and Chat since 30 September, with usage limits Microsoft has not published, per Microsoft's post of that date, which names Sonnet 5.5.
Choose Gemini 3.8 Flash for
- First-pass support replies
- Summarising documents, images and recordings at volume
- Routine multi-step tasks on a budget
Fast and well liked in blind votes for the money, at under half the list price of Gemini 4 Argon, but users report more made-up answers than rivals and Google doubles the price on 1 January 2027.
Caveats: $0.75 in / $3.75 out per million tokens (the unit vendors bill by) is introductory; Google's pricing page says $1.50 / $7.50 from 1 January 2027. Users report more invented facts and more dropped details between messages than with rival models: have someone check its output. Third Flash release in six weeks: expect Google to retire versions quickly and plan for re-testing. In the Gemini app it is for Google AI Pro and Ultra subscribers, per Google's launch post. Google Workspace is not listed: no Google page we read names the model and a Workspace plan.
What people running them say
Claude Sonnet 5.5: Less discussed than Opus or Haiku because it just works; the news was October's price cut for text it has already been sent once and reads again, to $0.10 per million tokens (the unit vendors bill by).
Gemini 3.8 Flash: A very large Hacker News (developer forum) thread: 1,160 upvotes, 669 comments. simonw had it build an interactive chart as a web page in '13 seconds' for '1.8 cents'; colechristensen calls it 'competitive with opus/fable and also FAST'; several use it for the bulk of the work while a stronger model writes the plan. The pushback is about reliability: one user says it 'gives me the most hallucinations' (made-up facts) of the major models, others complain it ignores what was said one message earlier, and in some subjects its knowledge stops at early 2025, which hurts research tasks.
Questions people ask
Which is better, Claude Sonnet 5.5 or Gemini 3.8 Flash?
Claude Sonnet 5.5 and Gemini 3.8 Flash are within three points on the Models at Work leaderboard, which we treat as a tie (66 vs 65 out of 100). On independent tests alone, Claude Sonnet 5.5 is ahead (68 vs 63). Gemini 3.8 Flash is cheaper: 1,000 support replies cost about $3.75 at list price, against $10 on Claude Sonnet 5.5, which is 2.7 times as much. On the Artificial Analysis Intelligence Index, one of the independent tests, Claude Sonnet 5.5 leads 55 to 31.
When should I choose Claude Sonnet 5.5 over Gemini 3.8 Flash?
Choose Claude Sonnet 5.5 for support replies at volume, drafting proposals and reports, summarising meetings and long documents, answering questions from company documents. A sound everyday default: 55 on Artificial Analysis's index, four points behind Claude Opus 5.5, at half its list price.
When should I choose Gemini 3.8 Flash over Claude Sonnet 5.5?
Choose Gemini 3.8 Flash for first-pass support replies, summarising documents, images and recordings at volume, routine multi-step tasks on a budget. Fast and well liked in blind votes for the money, at under half the list price of Gemini 4 Argon, but users report more made-up answers than rivals and Google doubles the price on 1 January 2027.
Which is cheaper, Claude Sonnet 5.5 or Gemini 3.8 Flash?
Claude Sonnet 5.5 costs $2 per million tokens it reads (input) and $10 per million tokens it writes (output) on Anthropic's list price (Claude pricing, read Nov 12, 2026). A token is about three-quarters of a word. Gemini 3.8 Flash costs $0.75 per million tokens it reads (input) and $3.75 per million tokens it writes (output) on Google's list price (Gemini API Pricing, read Nov 12, 2026). A token is about three-quarters of a word.
What do 1,000 jobs cost on Claude Sonnet 5.5 and Gemini 3.8 Flash?
At list price: 1,000 support replies cost $10 on Claude Sonnet 5.5 and $3.75 on Gemini 3.8 Flash; 1,000 documents processed cost $7 on Claude Sonnet 5.5 and $2.63 on Gemini 3.8 Flash; 1,000 calls summarised cost $26 on Claude Sonnet 5.5 and $9.75 on Gemini 3.8 Flash; 1,000 contracts reviewed cost $75 on Claude Sonnet 5.5 and $28 on Gemini 3.8 Flash; 1,000 drafts written cost $11 on Claude Sonnet 5.5 and $4.13 on Gemini 3.8 Flash. A product built on either model charges its own price on top.
Scores come from the Models at Work leaderboard: Score is 0 to 100 and computed, not typed. 40% is independent testing (Artificial Analysis, Arena, Scale, Epoch, Vals and others; each test is scaled against the best score on this board, and tests of real work, such as finished freelance projects or professional tasks, count double the exams). 30% is price: the vendor's list price for a typical mix of reading and writing, on a fixed scale from $0.05 to $60 per million tokens, so a model that costs a fifth as much gains real ground. 15% is what people report after running it, from Signals and linked threads. 15% is fit: how much text it can take in at once and where a business can get it (the products and clouds that carry it), with a small credit for open weights. A missing component drops out and the rest are reweighted. A model with no independent test yet is provisional and ranks below every measured one. Within three points is a tie. Vendor-published figures are labelled and never counted. Prices are vendor list prices where published; a typical mix assumes three parts reading to one part writing.