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Claude Sonnet 5.5 vs Gemini 3.8 Flash
Claude Sonnet 5.5 (September 28, 2026) is Anthropic’s mid-tier model for coding and agents; Gemini 3.8 Flash (September 2, 2026) is Google’s fast, low-cost tier. They sit in different classes, so the real question is when Flash is good enough to save the difference.
Price per 1M tokens
| Claude Sonnet 5.5 | Gemini 3.8 Flash | |
|---|---|---|
| Input | $2 | $0.75 ($1.50 from 2027) |
| Output | $10 | $3.75 ($7.50 from 2027) |
| Cached input | $0.10 | $0.075 |
| Batch discount | 50% | 50% (Batch or Flex) |
| Free API tier | No | Yes |
Source: Anthropic pricing
Source: Gemini API pricing
Cost of 1,000 requests
| 1,000 requests of | Claude Sonnet 5.5 | Gemini 3.8 Flash (2026) | Gemini 3.8 Flash (2027) |
|---|---|---|---|
| Chat reply (2K in / 500 out) | $9.00 | $3.38 | $6.75 |
| RAG answer (50K in / 1K out) | $110.00 | $41.25 | $82.50 |
| Long document (300K in / 4K out) | $640.00 | $240.00 | $480.00 |
Source: Anthropic pricing
Source: Gemini API pricing
Benchmarks: Artificial Analysis
Google’s own table compares 3.8 Flash with the older Claude Sonnet 5, not 5.5, so we use Artificial Analysis, which runs both models on the same tasks (read 2026-10-13):
| Model (effort) | Intelligence Index | Output speed | Cost per index task | Tokens to run the index |
|---|---|---|---|---|
| Claude Sonnet 5.5 (Max) | 56 | 135.5 tok/s | $5.46 | 420M |
| Gemini 3.8 Flash (High) | 41 | 131.5 tok/s | $1.24 | 170M |
Sonnet 5.5 leads by 15 points; Flash costs about a quarter as much per task and uses far fewer tokens. Output speed is similar.
Source: Artificial Analysis: Claude Sonnet 5.5
Source: Artificial Analysis: Gemini 3.8 Flash
Features side by side
| Claude Sonnet 5.5 | Gemini 3.8 Flash | |
|---|---|---|
| Model ID | claude-sonnet-5-5 | gemini-3.8-flash |
| Context / max output | 1M / 128K | 1M / 65,536 |
| Input types | Text and images | Text, images, video, audio, PDF |
| Coding tools | Claude Code, computer use | Antigravity, Android Studio, computer use (preview) |
| Web grounding | Web search tool | Google Search and Maps grounding |
| Knowledge cutoff | June 2026 | Not published |
Source: Anthropic models overview
Source: Gemini API model page
Which one should you use?
- Pick Sonnet 5.5. Multi-file coding, refactors, long agent runs and anything where a wrong answer costs more than the tokens.
- Pick Gemini 3.8 Flash. Routing, extraction, summaries, video or audio understanding and search-grounded answers at volume.
- Use both. A common setup: Flash (or Haiku 5.5) handles triage and simple steps, and hands the hard ones to Sonnet.
Gemini 3.8 Flash guide · Claude Sonnet 5.5 guide · Haiku 5.5 vs Gemini 3.8 Flash
FAQ
Is Gemini 3.8 Flash as good as Claude Sonnet 5.5?
No. Artificial Analysis scores Sonnet 5.5 at 56 and 3.8 Flash at 41. Flash is a cheaper, faster tier meant for volume work.
How much cheaper is Gemini 3.8 Flash than Sonnet 5.5?
Until December 31, 2026, $0.75 / $3.75 vs $2 / $10 per 1M tokens. From 2027 Flash is $1.50 / $7.50, still cheaper than Sonnet.
Which is better for coding?
Sonnet 5.5, especially for multi-file changes and long agent runs. Flash is fine for small edits, explanations and code review triage.
Independent guide, not affiliated with Google or Anthropic. Prices and benchmarks change; check the linked official pages before you commit to a budget.