Both are mid-tier workhorses with million-token windows. Gemini 3.8 Flash is on an introductory price through December 31, 2026, so the gap you see today will roughly halve in January.
Gemini 3.8 Flash is about 2.7× cheaper than Claude Sonnet 5.5 on input and output through December 31. From January 1, 2027 Flash's price doubles and the gap shrinks to about 1.3×. Flash also has a free API tier; Sonnet 5.5 has explicit cache controls and no scheduled price change.
| Claude Sonnet 5.5 | Gemini 3.8 Flash | |
|---|---|---|
| Provider | Anthropic | |
| Tier | Mid-tier | Mid-tier |
| Input / 1M tokens | $2.00 | $0.75 |
| Output / 1M tokens | $10.00 | $3.75 |
| Cache hit / 1M | $0.10 | $0.075 |
| Cache write / 1M | $2.50 | — |
| Context window | 1M | 1M |
| Notes | Released Sep 28, 2026, replacing Sonnet 5 at the identical $2/$10 per 1M price; Sonnet 5 is now a legacy model | On the Gemini API free and paid tiers; Gemini 3.7 Flash retired Oct 8, 2026 and now auto-routes here (requests still billed at this rate); intro price thru Dec 31, reverts to $1.50/$7.50 (cache $0.15) Jan 1 |
Gemini 3.8 Flash is 2.7× cheaper on input tokens ($0.75 vs $2.00 per 1M). Gemini 3.8 Flash is 2.7× cheaper on output tokens ($3.75 vs $10.00 per 1M).
| Workload | Claude Sonnet 5.5 | Gemini 3.8 Flash | Difference |
|---|---|---|---|
| Support chatbot 10,000 conversations × (2,000 input + 400 output tokens) | $80.00 | $30.00 | Gemini 3.8 Flash saves $50.00 |
| Document Q&A 1,000 questions × (30,000 input + 800 output tokens) | $68.00 | $25.50 | Gemini 3.8 Flash saves $42.50 |
| Coding agent session 4M input tokens (90% cache hits) + 150,000 output tokens | $2.66 | $1.13 | Gemini 3.8 Flash saves $1.53 |
Standard rates per 1M tokens from data on this site. The coding-agent row assumes 90% of input is read from the prompt cache (full input price where a model has no cache rate). Cache-write fees, batch discounts and long-context surcharges listed in the notes are not included. Updated November 2, 2026.
your evals favour it on your tasks, you want explicit control over what is cached and for how long, or you need a price that isn't scheduled to change.
you want the lowest cost per token on a mid-tier model, want to prototype on a free API tier, or you're on Google Cloud.
Google lists Flash's intro rate through December 31, 2026 and double that from January 1, 2027 — on input, output and cache hits. After that Flash is still cheaper than Sonnet 5.5, but by about a quarter rather than nearly two-thirds. If a migration is justified only by today's ratio, re-run the numbers at the 2027 rate.
Flash's cache hit ($0.075) is below Sonnet's ($0.10), but Google also bills cache storage by the hour. Anthropic charges a one-off write ($2.50 per 1M for a 5-minute cache, or 2× input for 1 hour). A cache kept warm all day costs more on Google's model than one written and read in short bursts.
Google's pricing page lists a free tier for Gemini 3.8 Flash (input, output and caching free of charge, subject to rate limits), useful for prototyping. Anthropic doesn't list a free API tier for Sonnet 5.5. Both providers halve rates for Batch jobs, and neither charges a long-context surcharge on these models.
About 2.7× on input and output at the intro rate through December 31, 2026, and about 1.3× after Flash's price doubles on January 1, 2027.
Google's Gemini API pricing page lists a free tier for Gemini 3.8 Flash, with paid rates above it.
No. Anthropic bills Sonnet 5.5's full window at standard rates, and Google lists no long-context tier for Gemini 3.8 Flash.
How we choose: prices come from each vendor's official pricing page and are re-checked every week. We take no affiliate fees, so rankings aren't for sale.