Gemini 3.5 Flash: price, context window, and caching
Launched in May 2026 as Google's agent and coding Flash, now called its legacy Flash for routine, high-throughput work.
Released May 19, 2026 · Prices as of September 28, 2026
In Google’s words
“Our legacy Flash model, providing baseline speed and foundational performance for routine, high-throughput workloads.”
Facts
Specs and prices
| Fact | Gemini 3.5 Flash |
|---|---|
| Maker | |
| API model id | gemini-3.5-flash |
| Released | May 19, 2026 |
| Status | Previous generation |
| Context window | 1.05M tokens |
| Max output | 65.5K tokens |
| Open weights | No |
| Input, per 1M tokens | $1.50 |
| Cache hit, per 1M | $0.15 |
| Cache write, per 1M | $1.50 (same as input) |
| Output, per 1M tokens | $9 |
| Runs in | Gemini CLI, OpenCode, OpenRouter, and GitHub Copilot |
Standard API rates in US dollars, as published by the maker on September 28, 2026. Batch and priority tiers, taxes, and subscription plans are not included.
Good to know
- While Gemini 3.6 to 3.8 Flash are on introductory rates, it costs more per token than they do.
- Gemini CLI uses it as the Flash model for Sign in with Google accounts that don't yet get the latest Flash.
Cost
What typical work costs
Example token counts at Gemini 3.5 Flash’s published rates. On the agentic session, caching saves $2.70 against billing every token as ordinary input.
| Agentic coding session, 100K input, 400K written to cache, 2M read from cache, 50K output | $1.50 |
|---|---|
| Large one-off review, 150K input with no cache hits, 10K output | $0.32 |
| Output-heavy generation, 30K input, 80K output | $0.77 |
| A month of sessions, 110 sessions: 5 a day, 22 working days | $165.00 |
Prompt caching
How Google bills cached tokens
Implicit caching is on by default for Gemini 2.5 and newer. When a request repeats a prefix Google has cached, the discount is applied automatically, but a hit is not guaranteed.
Explicit caching creates a cache you reference by name, with a guaranteed discount. It adds a storage charge for as long as the cache lives, 1 hour by default: $4.50 per million tokens per hour on Pro models and $0.50 to $1 on Flash models.
On every model compared here, a cache hit costs 10% of the input price. Google publishes no separate cache-write price, so this blog prices written tokens as ordinary input.
Source: Google: Context caching
Gemini 3.5 Flash compared
Claude Sonnet 5 vs Gemini 3.5 Flash
Gemini 3.5 Flash, now Google's legacy Flash, costs $1.50 against $2.40 on Claude Sonnet 5 per cached coding session. Most of the gap is cache writes.
Gemini 3.8 Flash vs Gemini 3.5 Flash
Gemini 3.8 Flash costs about half of Gemini 3.5 Flash on introductory rates. What changes on January 1, 2027, and which one Gemini CLI picks for you.
Your own numbers
See what Gemini 3.5 Flash really costs you.
everyaitoken reads your Gemini CLI, OpenCode, and OpenRouter history on your Mac and prices every request at API rates, with what caching saved or cost. $9 once.