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HEAD TO HEAD · UPDATED NOV 6, 2026
Claude Opus 5.5 vs Gemini 3.8 Flash
Anthropic against Google DeepMind, on sourced numbers only. Green marks the higher (or cheaper) value on each row; the text below only calls a lead when the gap is bigger than measurement noise.
| Claude Opus 5.5 | Gemini 3.8 Flash | |
|---|---|---|
| Arena Elo | 1509 source ↗ | 1496 source ↗ |
| GPQA Diamond | 90.6% source ↗ | 95.4% source ↗ |
| $ per 1M in / out | $4 / $20 source ↗ | $0.75 / $3.75 source ↗ |
| Blended $ per 1M (3:1) | $8.00 source ↗ | $1.50 source ↗ |
| Context window | 1M source ↗ | 1M source ↗ |
| Output speed | 110 tok/s source ↗ | 117 tok/s source ↗ |
| Released | Sep 22, 2026 source ↗ | Sep 2, 2026 source ↗ |
| Open weights | No source ↗ | No source ↗ |
| Reasoning effort tiers | low · medium · high · xhigh · max (default: medium) | low · medium · high (default: medium) |
| API effort control | output_config={"effort": "low" | "medium" | "high" | "xhigh" | "max"} source ↗ | thinking_config={"thinking_level": "low" | "medium" | "high"} source ↗ |
| Additional benchmarks | Arena WebDev: 1810 (#1) source ↗ SWE-bench Pro: 89.9% source ↗ Terminal-Bench 4.0: 66.4% (xhigh) source ↗ GDPval-AA v2.1: 1846 source ↗ CursorBench 4.0: 57.8% at max effort, 52.5% at default source ↗ AA Intelligence Index v5.0.1: 59 source ↗ | DeepSWE v1.1: 73.7% source ↗ |
| Best for (workload) | Anthropic suggests starting with Opus 5.5 for most workloads. #1 on Arena WebDev (1810); 66.4% on Terminal-Bench 4.0 at xhigh effort (Anthropic). source ↗ | 95.4% on GPQA Diamond (Epoch AI) and 117 tok/s output (Artificial Analysis) at a Flash-tier price. source ↗ |
Arena Elo from the arena.ai text leaderboard as of Oct 27, 2026 source ↗. Speed measured by Artificial Analysis and varies by provider.
Which one should I use?
For high-volume work where cost matters most, Gemini 3.8 Flash is about 5.3 times cheaper per token. For hard science and analysis questions, Gemini 3.8 Flash scores higher on GPQA Diamond (95.4% vs 90.6%). On release timing, Anthropic is at day 30 of a typical ~15-day gap (PAST TYPICAL GAP), and Google DeepMind is at day 24 of a typical ~32-day gap (MID-CYCLE).
Key differences from the sourced numbers
- Gemini 3.8 Flash is the cheaper option: $1.50 vs $8.00 per 1M tokens at a 3:1 input-to-output mix (about 5.3 times less).
- On the Arena text leaderboard they are close (1509 vs 1496): a gap under 20 points is within the leaderboard's margin of error.
- On GPQA Diamond, graduate-level science questions, Gemini 3.8 Flash leads 95.4% to 90.6%.
- Claude Opus 5.5 pricing note: Same rate across the full 1M context window.
- Gemini 3.8 Flash pricing note: Until Dec 31, 2026; $1.50 / $7.50 from Jan 1, 2027. No higher rate for long prompts.
Frequently asked questions
Is Claude Opus 5.5 or Gemini 3.8 Flash better?
Gemini 3.8 Flash is the cheaper option: $1.50 vs $8.00 per 1M tokens at a 3:1 input-to-output mix (about 5.3 times less). On the Arena text leaderboard they are close (1509 vs 1496): a gap under 20 points is within the leaderboard's margin of error. On GPQA Diamond, graduate-level science questions, Gemini 3.8 Flash leads 95.4% to 90.6%. Claude Opus 5.5 pricing note: Same rate across the full 1M context window. Gemini 3.8 Flash pricing note: Until Dec 31, 2026; $1.50 / $7.50 from Jan 1, 2027. No higher rate for long prompts.
Which one should I use: Claude Opus 5.5 or Gemini 3.8 Flash?
For high-volume work where cost matters most, Gemini 3.8 Flash is about 5.3 times cheaper per token. For hard science and analysis questions, Gemini 3.8 Flash scores higher on GPQA Diamond (95.4% vs 90.6%). On release timing, Anthropic is at day 30 of a typical ~15-day gap (PAST TYPICAL GAP), and Google DeepMind is at day 24 of a typical ~32-day gap (MID-CYCLE).
How much does Claude Opus 5.5 cost compared with Gemini 3.8 Flash?
Claude Opus 5.5 lists at $4 / $20 per 1M input/output tokens ($8.00/1M blended at 3:1). Gemini 3.8 Flash lists at $0.75 / $3.75 per 1M input/output tokens ($1.50/1M blended at 3:1).
Facts checked Nov 5, 2026 against official sources. Every number links to its source. Spotted an error? Email [email protected].