Claude Opus 5.5 vs Gemini 3.5 Flash: pricing and benchmarks
Gemini 3.5 Flash is 63% cheaper on input tokens ($1.50 vs $4.00 per 1M). Gemini 3.5 Flash is 55% cheaper on output tokens ($9.00 vs $20.00 per 1M). On our document Q&A workload (50,000 questions a month), Gemini 3.5 Flash costs $870.00 a month versus $2,200 for Claude Opus 5.5, 60% less. Epoch AI has not published a capability index score for Claude Opus 5.5 yet.
Prices verified September 26, 2026.
Which should you choose?
Epoch AI has not published a capability index score for Claude Opus 5.5 yet.
Gemini 3.5 Flash costs $3.375 per 1M tokens (3:1 input-to-output mix) vs $8.00 for Claude Opus 5.5, 58% less.
Pricing and specs
| Claude Opus 5.5 | Gemini 3.5 Flash | |
|---|---|---|
| Provider | Anthropic | |
| API model ID | claude-opus-5-5 | gemini-3.5-flash |
| Input / 1M tokens | $4.00 | $1.50 |
| Cached input / 1M tokens | $0.20 | $0.15 |
| Output / 1M tokens | $20.00 | $9.00 |
| Long-context rates | — | — |
| Context window | 1M tokens | 1.05M tokens |
| Max output | 128K tokens | 66K tokens |
| Batch discount | 50% off | 50% off |
Benchmarks
| Claude Opus 5.5 | Gemini 3.5 Flash | |
|---|---|---|
| Epoch Capabilities Index | — | 154.7 |
| GPQA Diamond· Science reasoning | — | 90.4% |
| FrontierMath (Tiers 1–3)· Advanced math | — | 62.8% |
| SimpleQA Verified· Factual accuracy | — | 66.2% |
| ARC-AGI-2· Abstract reasoning | — | 72.1% |
| DeepSWE· Coding | — | 37.4% |
| APEX-Agents· Agentic work | — | — |
Source: Epoch AI, best recorded result per model (CC BY 4.0). A dash means no published score. See all benchmarks
Monthly cost for real workloads
| Workload | Claude Opus 5.5 | Gemini 3.5 Flash | Difference |
|---|---|---|---|
Support chatbot 100,000 replies a month, ~1,500 input tokens (system prompt + history) and ~400 output tokens each. | $1,400 | $585.00 | Gemini 3.5 Flash 58% cheaper |
Document Q&A (RAG) 50,000 questions a month with ~8,000 tokens of retrieved context and ~600 output tokens each. | $2,200 | $870.00 | Gemini 3.5 Flash 60% cheaper |
Coding agent 10,000 agent steps a month, ~40,000 input tokens each (70% read from the prompt cache) and ~2,000 output tokens. | $936.00 | $402.00 | Gemini 3.5 Flash 57% cheaper |
Estimates use standard list prices and ignore cache-write surcharges. Different tokenizers can count the same text differently, so test with your own prompts.
Claude Opus 5.5 vs Gemini 3.5 Flash cost calculator
- $870.00/mo$0.02 / request
- Claude Opus 5.5Anthropic$2,200/mo$0.04 / request
Standard-tier list prices. Long-context rates apply automatically where the provider publishes a threshold. Excludes cache-write surcharges, taxes, batch and volume discounts.
Claude Opus 5.5 pricing notes
Anthropic’s recommended default model for most workloads, with adaptive thinking always on.
- Cache reads cost 5% of the input price, against 10% on Claude Opus 5 and Sonnet 5.
- Cache writes cost $5 (5-minute cache) or $8 (1-hour cache) per 1M tokens.
- US-only inference (inference_geo: "us") costs 1.1x.
Gemini 3.5 Flash pricing notes
Google’s Gemini 3.5 Flash model, with thinking, tool use and a 1M-token context window.
- Output price includes thinking tokens.
- Context cache storage costs $1.00 per 1M tokens per hour.
- Priority inference costs 1.8x the standard rate.
Frequently asked questions
- Is Claude Opus 5.5 cheaper than Gemini 3.5 Flash?
- Gemini 3.5 Flash is 63% cheaper on input tokens ($1.50 vs $4.00 per 1M). Gemini 3.5 Flash is 55% cheaper on output tokens ($9.00 vs $20.00 per 1M). On our document Q&A workload (50,000 questions a month), Gemini 3.5 Flash costs $870.00 a month versus $2,200 for Claude Opus 5.5, 60% less.
- Which is more capable, Claude Opus 5.5 or Gemini 3.5 Flash?
- Epoch AI has not published a capability index score for Claude Opus 5.5 yet.
- How much does Claude Opus 5.5 cost per 1M tokens?
- Claude Opus 5.5 costs $4.00 per 1M input tokens and $20.00 per 1M output tokens, and $0.20 per 1M cached input tokens on Anthropic’s standard tier.
- How much does Gemini 3.5 Flash cost per 1M tokens?
- Gemini 3.5 Flash costs $1.50 per 1M input tokens and $9.00 per 1M output tokens, and $0.15 per 1M cached input tokens on Google’s standard tier.
- Which has the larger context window, Claude Opus 5.5 or Gemini 3.5 Flash?
- Gemini 3.5 Flash has the larger context window: 1.05M tokens versus 1M for Claude Opus 5.5.