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Claude Sonnet 5 vs Gemini 3.8 Flash
A straight cost comparison of Claude Sonnet 5 (Anthropic) and Gemini 3.8 Flash (Google Gemini), per 1,000,000 tokens, verified October 2026.
Rate-by-rate comparison
| Metric | Claude Sonnet 5 | Gemini 3.8 Flash | Winner |
|---|---|---|---|
| Input / 1M | $2 | $0.75 | Gemini 3.8 Flash |
| Cached input / 1M | $0.20 | $0.075 | Gemini 3.8 Flash |
| Cache write / 1M | $2.50 | — | Gemini 3.8 Flash |
| Output / 1M | $10 | $3.75 | Gemini 3.8 Flash |
| Context window | 1,000,000 | 1,000,000 | Tie |
| Batch API | Yes | Yes | Tie |
| Long-context tier | None | > 200,000 | — |
For per-token metrics, the lower number wins. For context window and batch support, the higher or broader option wins. A dash means the provider does not publish that rate: a missing cache-write fee means writes are not billed per token, while a missing cached-input rate means cache hits bill at the full input rate.
Blended cost: 1M input + 250K output
| Model | Blended cost | Difference |
|---|---|---|
| Claude Sonnet 5 | $4.50 | +$2.81 |
| Gemini 3.8 Flash | $1.69 | Cheaper |
Three workloads, two bills
| Workload | Claude Sonnet 5 | Gemini 3.8 Flash | Winner |
|---|---|---|---|
| Support chat 1,000 requests · 4K input / 600 output | $14 | $5.25 | Gemini 3.8 Flash |
| RAG with caching 1,000 requests · 50K input (45K cached) / 1K output | $29.10 | $10.91 | Gemini 3.8 Flash |
| Nightly batch job 10,000 requests · 10K input / 2K output | $200 | $75 | Gemini 3.8 Flash |
Which one should you pick?
Claude Sonnet 5 wins on none of the three workloads above, while Gemini 3.8 Flash wins on support chat, cached RAG, nightly batch job.
Beyond price, the two differ on input rate ($2 vs $0.75); output rate ($10 vs $3.75); cached-input rate ($0.20 vs $0.075); cache-write rate ($2.50 vs —); long-context tier (none vs yes, above 200,000).
Batch mode is available on Claude Sonnet 5 and Gemini 3.8 Flash, which halves the nightly job. Both publish cached-input discounts, so a stable system prompt is worth caching on either.
FAQ
Is Claude Sonnet 5 cheaper than Gemini 3.8 Flash?
On a blended 1M-input-plus-250K-output workload, Gemini 3.8 Flash is cheaper by 63% ($1.69 vs $4.50). The gap changes for cache-heavy prompts and for batch jobs, as the workload table shows.
Which handles longer prompts, Claude Sonnet 5 or Gemini 3.8 Flash?
Both models share the same 1,000,000-token context window. Watch the long-context threshold on Gemini 3.8 Flash: rates rise once input passes it.
Do both models support prompt caching?
Claude Sonnet 5 bills cached reads at $0.20 per 1M; Gemini 3.8 Flash at $0.075.