Model comparison
Claude Sonnet 5.5 vs Gemini 3.8 Flash: pricing, context and features compared
Claude Sonnet 5.5 costs $2 per million input tokens and $10 per million output tokens; Gemini 3.8 Flash costs $0.75 and $3.75. Here is how they compare on specs, on what real workloads cost, and on which to pick for what, from prices updated daily.
Developers weigh Gemini’s Flash model against Claude Sonnet when Sonnet’s quality is more than a task needs. Both read very long prompts, so the comparison comes down to price, inputs and features.
- Input / 1M
- $2
- Output / 1M
- $10
- Context
- 1,000,000
- Max output
- 128,000
- Input / 1M
- $0.75
- Output / 1M
- $3.75
- Context
- 1,048,576
- Max output
- 65,536
Verdict
Claude Sonnet 5.5 or Gemini 3.8 Flash: which to pick
Gemini 3.8 Flash has the lower list prices: 2.7× cheaper per input token and 2.7× per output token. On our data, Claude Sonnet 5.5 has the edge for long replies, and Gemini 3.8 Flash for the lowest bill, very long prompts, non-text inputs, repeated prompts and batch jobs. For scale, a support chatbot handling 1,000 requests a day costs about $169.57 a month on Claude Sonnet 5.5 and $64.45 on Gemini 3.8 Flash.
- Lowest bill for typical workloadsPick Gemini 3.8 Flash
- Gemini 3.8 Flash costs less on all 4 workloads below, 2.5× to 2.7× cheaper than Claude Sonnet 5.5 at list prices.
- Very long prompts (whole codebases, long documents)Pick Gemini 3.8 Flash
- Both read about 1,000,000 tokens per request. One 800,000-token prompt with a 2,000-token reply costs $1.62 on Claude Sonnet 5.5 and $0.61 on Gemini 3.8 Flash. Neither has a long-prompt surcharge in our data.
- Long replies (reports, large code files)Pick Claude Sonnet 5.5
- Claude Sonnet 5.5 can write up to 128,000 tokens in one reply, against 65,536 for Gemini 3.8 Flash.
- Images, audio, video or files in the promptPick Gemini 3.8 Flash
- Gemini 3.8 Flash also accepts audio and video, which Claude Sonnet 5.5 doesn’t.
- Repeated long prompts (prompt caching)Pick Gemini 3.8 Flash
- Gemini 3.8 Flash bills cached input at $0.075 per 1M (10% of its input price), against $0.10 per 1M (5% of its input price) for Claude Sonnet 5.5.
- Overnight batch jobsPick Gemini 3.8 Flash
- Both offer batch prices; on the document summariser workload Gemini 3.8 Flash costs $37.64 a month against $100.38.
- Self-hosting or choosing your own hostEither
- Neither has downloadable weights: both are only available through their provider’s API and cloud partners.
Criteria use only list prices, published limits and the features each provider declares. We don’t rank answer quality; test both models on your own prompts before you commit.
Specs
Claude Sonnet 5.5 vs Gemini 3.8 Flash side by side
| Spec | Claude Sonnet 5.5 | Gemini 3.8 Flash |
|---|---|---|
| Provider | Anthropic | |
| Input / 1M tokens | $2 | $0.75 (better) |
| Output / 1M tokens | $10 | $3.75 (better) |
| Cached input / 1M | $0.10 | $0.075 (better) |
| Cache write / 1M | $2.50 | No write charge listed |
| Batch in / out | $1 / $5 | $0.375 / $1.875 (better) |
| Long-prompt price | None | None |
| Context window | 1,000,000 | 1,048,576 |
| Max output | 128,000 (better) | 65,536 |
| Accepts | text, images, files | text, images, files, audio, video |
| Image input | Yes | Yes |
| Tool calling | Yes | Yes |
| Reasoning mode | Yes | Yes |
| Prompt caching | Yes | Yes |
| Structured output | Yes | Yes |
| Open weights | No | No |
| Knowledge cutoff | Not published | Not published |
| First listed | 2026-09-28 | 2026-09-02 |
Prices in US dollars per million tokens. Highlighted: the lower price or larger limit where the difference is over 5%. Features are as declared by each provider’s API; “First listed” is when our data source first listed the model. Long-prompt prices apply to the whole request once the prompt passes the threshold.
Costs
What Claude Sonnet 5.5 and Gemini 3.8 Flash cost for real workloads
| Workload | Tokens in / out | Requests/day | Claude Sonnet 5.5 / month | Gemini 3.8 Flash / month | Cheaper |
|---|---|---|---|---|---|
| Support chatbotCalculator: Claude Sonnet 5.5 · Gemini 3.8 Flash | 1,500 / 400 | 1,000 | $169.5750% cached | $64.4550% cached | Gemini 3.8 Flash (2.6×) |
| RAG appCalculator: Claude Sonnet 5.5 · Gemini 3.8 Flash | 6,000 / 500 | 500 | $223.8720% cached | $84.6320% cached | Gemini 3.8 Flash (2.6×) |
| Coding agentCalculator: Claude Sonnet 5.5 · Gemini 3.8 Flash | 40,000 / 2,000 | 200 | $238.4780% cached | $96.7380% cached | Gemini 3.8 Flash (2.5×) |
| Document summariserCalculator: Claude Sonnet 5.5 · Gemini 3.8 Flash | 8,000 / 600 | 300 | $100.38batch | $37.64batch | Gemini 3.8 Flash (2.7×) |
Each row uses the same token counts for both models and list prices, with caching and batch discounts only where the provider publishes them. A month is 365 ÷ 12 days. The support chatbot reads 50% of its prompt from the cache. The RAG app reads 20% of its prompt from the cache. The coding agent reads 80% of its prompt from the cache. The document summariser runs as a batch job where a batch price exists. Open either model in the LLM cost calculator to change any number.
Tokenizers
Are their per-token prices comparable?
Not exactly. Each model splits text into tokens its own way, so the same prompt can be a different number of tokens on Claude Sonnet 5.5 and Gemini 3.8 Flash, and the cheaper per-token price isn’t always the cheaper bill. The last column converts each output price into a price per million English words, which is the fairer comparison for prose.
| Model | Tokenizer | Tokens per 1,000 words | Output per 1M words |
|---|---|---|---|
| Claude Sonnet 5.5 | Claude (Opus 4.7 and later)Provider’s published figure | 1,802 | $18.02 |
| Gemini 3.8 Flash | GeminiOur measurement | 1,186 | $4.45 |
English prose, measured on the Universal Declaration of Human Rights (2026-10-11) or taken from the provider’s published words-per-token figure. Code, JSON and other languages use more tokens per word. Count your own text in the token counter or convert with tokens to words.
FAQ
Claude Sonnet 5.5 vs Gemini 3.8 Flash questions
Is Claude Sonnet 5.5 cheaper than Gemini 3.8 Flash?
Claude Sonnet 5.5 costs $2 per million input tokens and $10 per million output tokens; Gemini 3.8 Flash costs $0.75 and $3.75. For a support chatbot handling 1,000 requests a day, that is about $169.57 a month on Claude Sonnet 5.5 against $64.45 on Gemini 3.8 Flash, so Gemini 3.8 Flash is 2.6× cheaper there. Try your own numbers in the LLM cost calculator.
Which has the bigger context window, Claude Sonnet 5.5 or Gemini 3.8 Flash?
Their context windows are about the same size. Claude Sonnet 5.5 reads up to 1,000,000 tokens (roughly 750,000 English words) and writes up to 128,000 tokens per reply. Gemini 3.8 Flash reads up to 1,048,576 tokens (roughly 786,432 English words) and writes up to 65,536 tokens per reply. The window is shared between your prompt and the reply. Word counts use a rough 0.75 words per token; real ratios depend on the tokenizer.
Is Claude Sonnet 5.5 or Gemini 3.8 Flash better for coding?
We don’t publish benchmark scores, so this page can’t say which writes better code. What we can show is cost: a coding agent re-sending 40,000 tokens of context (80% cached) and writing 2,000 tokens, 200 times a day, costs about $238.47 a month on Claude Sonnet 5.5 and $96.73 on Gemini 3.8 Flash. Both support tool calling. Test both on tasks from your own repository.
Can Claude Sonnet 5.5 and Gemini 3.8 Flash read images?
Claude Sonnet 5.5 accepts images and files as well as text. Gemini 3.8 Flash accepts images, files, audio and video as well as text. So both can read screenshots, photos and scanned pages. This is what each provider declares for its API, not a measure of how well it works.
Are Claude Sonnet 5.5 and Gemini 3.8 Flash open source?
No. Neither Claude Sonnet 5.5 nor Gemini 3.8 Flash has published weights: you can only use them through Anthropic’s and Google’s APIs and their cloud partners. If you need a model you can host yourself, compare open-weight options in the model comparison table.
Do Claude Sonnet 5.5 and Gemini 3.8 Flash count tokens the same way?
Not necessarily. Each model splits text into tokens with its own tokenizer, so the same prompt can be a different number of tokens on each, and per-token prices aren’t directly comparable. Claude Sonnet 5.5 uses about 1,802 tokens per 1,000 English words (the provider’s published figure). Gemini 3.8 Flash uses about 1,186 tokens per 1,000 English words (our measurement). Count your own text with the token counter or convert with tokens to words.