Claude Sonnet 5 vs Gemini 3.5 Flash
Anthropic's Claude Sonnet 5 and Google's Gemini 3.5 Flash both target production language workloads, but they price and behave differently. Here is the side-by-side.
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The short answer
Gemini 3.5 Flash is the cheaper option — roughly 1.2x less on a blended workload, and it suits agentic loops and sub-agent fleets. Claude Sonnet 5 justifies its premium when you need fast claude-quality reasoning at scale.
Anthropic • Claude 5
$2.00 / $10.00
/ 1M tokens (input / output)
The workhorse Claude tier: a full million tokens of context and adaptive thinking at $2/$10, which undercuts the previous Sonnet 4.6 generation by a third on input while raising the context ceiling fivefold. The default pick for latency-sensitive products that still want Claude's writing and tool-use behaviour.
Google • Gemini 3.5
$1.50 / $9.00
/ 1M tokens (input / output)
Google's most capable Flash model, tuned for the agentic era: sub-agent deployment, multi-step workflows, and rapid coding iterations at scale. Supports search grounding, function calling, structured outputs, and computer use in preview. Note that it is pricier than the Gemini 3 Flash preview it replaced.
Input price
Gemini 3.5 Flash is 25% cheaper than Claude Sonnet 5 on input tokens.
Output price
Gemini 3.5 Flash is 10% cheaper than Claude Sonnet 5 on output tokens — usually the side that dominates the bill.
Monthly cost at three workload sizes
Standard (non-batch, non-cached) rates. Reasoning models will exceed these figures because thinking tokens bill as output.
| Workload | Claude Sonnet 5 | Gemini 3.5 Flash | Difference |
|---|---|---|---|
| Light — 1M in / 200K out | $4 | $3 | $1 |
| Moderate — 10M in / 2M out | $40 | $33 | $7 |
| Heavy — 100M in / 20M out | $400 | $330 | $70 |
Specification comparison
| Attribute | Claude Sonnet 5 | Gemini 3.5 Flash |
|---|---|---|
| Input (/ 1M tokens) | $2.00 | $1.50 |
| Output (/ 1M tokens) | $10.00 | $9.00 |
| Cached input | $0.20 | — |
| Context window | 1,000,000 tokens | 1,048,576 tokens |
| Max output | 128,000 tokens | 65,536 tokens |
| Native reasoning | Yes | Yes |
| Knowledge cutoff | 2026-01 | 2025-01 |
| Relative latency | low | low |
| Open weights | No | No |
| API model ID | claude-sonnet-5 | gemini-3.5-flash |
| Status | stable | stable |
Gemini 3.5 Flash: Flat rate at any context length, unlike Gemini 3.1 Pro's 200K cliff.
Choose Claude Sonnet 5 if…
- Production chat and copilots
- Long-document analysis
- Tool-heavy agents needing fast turns
- Code review and PR automation
Choose Gemini 3.5 Flash if…
- Sub-agent fleets and orchestration
- Fast coding iteration loops
- Search-grounded answers
- Multimodal ingestion at scale
Frequently asked
Is Claude Sonnet 5 or Gemini 3.5 Flash cheaper?
Gemini 3.5 Flash is cheaper. On a blended 3:1 input-to-output workload it costs about 1.2x less than Claude Sonnet 5.
Which has the larger context window, Claude Sonnet 5 or Gemini 3.5 Flash?
Gemini 3.5 Flash has the larger window at 1.05M tokens versus 1M.
Should I use Claude Sonnet 5 or Gemini 3.5 Flash?
Pick Claude Sonnet 5 for fast claude-quality reasoning at scale. Pick Gemini 3.5 Flash for agentic loops and sub-agent fleets. If cost dominates the decision, Gemini 3.5 Flash wins; if you need the capability ceiling, benchmark both on your own evals before committing.