Gemini 3.5 Flash vs o3
Gemini 3.5 Flash 
o3 Verdict
- Gemini 3.5 Flash (medium) leads on quality: 64.0 vs 61.6.
- Gemini 3.5 Flash (medium) is stronger in composite, human preference, instruction following, knowledge, multimodal, reasoning.
- o3 is stronger in agents & tools, coding, long context, maths.
- They cost about the same ($3.38 per 1M blended).
- Gemini 3.5 Flash (medium) streams 2.1× faster (226 vs 107 tokens per second).
| Metric | Gemini 3.5 Flash (medium) | o3 |
|---|---|---|
| BenchLeader Index | 64.0 | 61.6 |
| Agents & tools score | 68.0 | 70.3 |
| Coding score | 58.7 | 62.0 |
| Composite score | 71.6 | 54.5 |
| Human preference score | 67.5 | 62.3 |
| Instruction following score | 72.5 | 65.0 |
| Knowledge score | 74.2 | 58.0 |
| Long context score | 63.6 | 63.8 |
| Multimodal score | 67.6 | 57.9 |
| Reasoning score | 67.0 | 61.5 |
| Maths score | – | 78.6 |
| Blended price $/M | $3.38 | $3.50 |
| Output speed | 226 tok/s | 107 tok/s |
| Time to first answer | 12.0 s | 6.3 s |
| Context window | 1.0M | 200k |
| Epoch Capabilities Index | – | 146.9 |
| LMArena Text | 1474 | 1432 |
| LMArena Hard Prompts | 1493 | 1441 |
| LMArena Coding | 1502 | 1460 |
| LMArena WebDev | 1492 | – |
| LMArena Vision | 1306 | 1214 |
| AA Intelligence Index | 33.6 | 20.2 |
| IFBench | 74.6% | 71.4% |
| AA-LCR | 74.3% | 74.7% |
| MMMU-Pro | 83.9% | 70.1% |
| AA-Omniscience | 20.8 | -15.6 |
| Terminal-Bench Hard | 39.4% | 37.1% |
| GPQA Diamond (AA) | 92.1% | 82.7% |
| Humanity's Last Exam (AA) | 41.3% | 20.1% |
| τ²-Bench Telecom (AA) | 95.6% | 80.7% |
| PRBench Finance | – | 47.7% |
| PRBench Legal | – | 48.6% |
| MMMU (validation) | – | 82.9% |
| MMMU-Pro (official) | – | 76.4% |
| Kagi LLM Benchmark | – | 67.6% |
| IFEval (HELM) | – | 86.9% |
| Omni-MATH (HELM) | – | 71.4% |
| WildBench (HELM) | – | 86.1% |
| MMLU-Pro (HELM) | – | 85.9% |
| GPQA Diamond (HELM) | – | 75.3% |
| HELM Capabilities mean | – | 81.1% |
| Aider Polyglot | – | 81.3% |
| SWE-bench Verified (bash only) | – | 58.4% |
| SWE-bench Verified (any scaffold) | – | 58.4% |
| BFCL Overall | – | 63.0% |
Data as of 2026-09-12. Best configuration of each model; every score links to its source on the model pages.
Gemini 3.5 Flash vs o3: questions
- Is Gemini 3.5 Flash better than o3?
- Gemini 3.5 Flash (medium) leads on quality: 64.0 vs 61.6. The BenchLeader Index combines every independent quality benchmark; Gemini 3.5 Flash (medium) is ahead overall as of 2026-09-12, but check the category scores for your use.
- Is Gemini 3.5 Flash better than o3 for coding?
- o3 scores higher in coding (62 vs 59 on the category index, where 50 is average).
- Is Gemini 3.5 Flash better than o3 for agentic tasks?
- o3 scores higher in agentic tasks (70 vs 68 on the category index, where 50 is average).
- Which is cheaper, Gemini 3.5 Flash or o3?
- Gemini 3.5 Flash is cheaper: $3.38 against $3.50 per million tokens, blended at three input tokens per output token.
- Which is faster, Gemini 3.5 Flash or o3?
- Gemini 3.5 Flash streams faster: 226 against 107 output tokens per second.
- Which has the larger context window?
- Gemini 3.5 Flash accepts more context: 1.0M against 200k tokens.