Gemini 2.5 Flash vs o3
o3 leads Gemini 2.5 Flash on the Artificial Analysis Intelligence Index, 20.2 to 15.5, and Gemini 2.5 Flash costs 3.2x less per output token ($2.50 vs $8.00 per million). Updated October 22, 2026; 68 benchmarks have a result for both.
Gemini 2.5 Flash or o3: which to pick
Neither model has a coding score yet, so the two cannot be ranked on coding.
Pick Gemini 2.5 Flash for output tokens 3.2x cheaper ($2.50 vs $8.00 per million) and a lower cost per solved task ($0.466 against $0.571).
- Shared results
- 68
- Gemini 2.5 Flash only
- 5
- o3 only
- 34
- Like-for-like categories
- 8 of 9
Only benchmarks that tested both models count toward a pick; a result only one model has is shown but not compared.
Which one for your work
Each card is decided by one number both models carry. Where only one has it, the card says so and makes no call.
Coding
Vibe Coding Index, six public coding benchmarks
No call
Neither has a coding score yet.
One side not measured
Intelligence
AA Intelligence Index
o3
o3 leads, 20.2 against 15.5.
Same board, both measured
Reasoning
GPQA Diamond
No call
Only o3 has a GPQA Diamond result, 84.1%.
Directional only
Math
AIME
No call
Only o3 has a AIME result, 85.3%.
Directional only
Knowledge
MMLU Pro
No call
Only o3 has a MMLU Pro result, 85.6%.
Directional only
Web design
Design Arena: websites
Gemini 2.5 Flash
Gemini 2.5 Flash leads, 1074 against 1036.
Same board, both measured
Long documents
Listed context window
Gemini 2.5 Flash
Gemini 2.5 Flash takes 1.05M tokens against 200K.
Listed by OpenRouter
Everyday cost
1K input + 500 output tokens
Gemini 2.5 Flash
Gemini 2.5 Flash $0.0015, o3 $0.0060 per turn.
List prices
Cost per solved task
One SWE-bench Verified task, solved
Gemini 2.5 Flash
Gemini 2.5 Flash $0.466, o3 $0.571.
Published attempt cost and pass rate
At a glance
- Coding index
- Gemini 2.5 Flash not benchmarked, o3 not benchmarked.
- Widest category
- Agentic work, 27.3 points apart on average over 3 shared benchmarks.
- Widest single gap
- τ²-Bench Telecom: Gemini 2.5 Flash 31.6% against o3 80.7%, 49.1 points apart on a 0 to 100 scale.
- Output price
- Gemini 2.5 Flash $2.50 against o3 $8.00 per million output tokens, 3.2x apart.
- Context window
- Gemini 2.5 Flash takes 1.05M tokens, o3 200K.
Benchmark by benchmark
First the score: boards each model leads, per category, where both have a result. Then every board, a category to a fold; bars are each result on a 0 to 100 scale, so compare the two in a row, not one row with another.
| Category | Gemini 2.5 Flash | Bars | o3 | Ties |
|---|---|---|---|---|
| Coding | 2 | 3 | ||
| Intelligence | 0 | 2 | ||
| Agentic work | 0 | 3 | ||
| Reasoning | 5 | 6 | ||
| Math | 0 | 4 | ||
| Knowledge | 4 | 3 | ||
| Web design | 2 | 3 | ||
| General | 24 | 7 | ||
| All shared boards | 37 | 31 |
CodingLike-for-likeSix of these boards feed the Vibe Coding Index23
| Benchmark | Gemini 2.5 Flash | o3 | Leader |
|---|---|---|---|
| Aider polyglot | Not measured | 81.3% | Only o3 measured |
| SWE-bench Verified | 28.7% | 58.4% | o3 |
| SWE-bench Multimodal | Not measured | 36.0% | Only o3 measured |
| LiveCodeBench (Vals AI) | Not measured | 83.9% | Only o3 measured |
| LiveCodeBench (Artificial Analysis run) | 69.5% | 80.8% | o3 |
| Terminal-Bench Hard (Artificial Analysis run) | 13.6% | 37.1% | o3 |
| Terminal-Bench | 17.1% | Not measured | Only Gemini 2.5 Flash measured |
| GSO-Bench | Not measured | 8.8% | Only o3 measured |
| WeirdML | Not measured | 52.4% | Only o3 measured |
| ALE-Bench | Not measured | 933.5 | Only o3 measured |
| LMArena Text: coding | 1423 | 1407 | Gemini 2.5 Flash |
| LMArena Text: software and IT | 1425 | 1415 | Gemini 2.5 Flash |
| SciCode | Not measured | 9.2% | Only o3 measured |
| Neither model has a result on the other 26 boards here | |||
IntelligenceLike-for-likePublic boards, shown as published, kept out of the index02
| Benchmark | Gemini 2.5 Flash | o3 | Leader |
|---|---|---|---|
| AA Intelligence Index | 15.5 | 20.2 | o3 |
| Epoch Capabilities Index | 142.9 | 146.7 | o3 |
Agentic workLike-for-likePublic boards, shown as published, kept out of the index03
| Benchmark | Gemini 2.5 Flash | o3 | Leader |
|---|---|---|---|
| τ²-Bench Telecom | 31.6% | 80.7% | o3 |
| METR time horizons | Not measured | 65.4% | Only o3 measured |
| GDPval | Not measured | 30.8% | Only o3 measured |
| BALROG | 33.5% | Not measured | Only Gemini 2.5 Flash measured |
| DeepResearch Bench | Not measured | 45.2% | Only o3 measured |
| OSWorld | Not measured | 23.0% | Only o3 measured |
| Vending-Bench 2 | $549 | Not measured | Only Gemini 2.5 Flash measured |
| Berkeley Function Calling Leaderboard (BFCL) | 56.2% | 63.0% | o3 |
| BrowseComp-Plus | 39.9% | 65.9% | o3 |
| Neither model has a result on the other 32 boards here | |||
ReasoningLike-for-likePublic boards, shown as published, kept out of the index56
| Benchmark | Gemini 2.5 Flash | o3 | Leader |
|---|---|---|---|
| GPQA Diamond | Not measured | 84.1% | Only o3 measured |
| MMMU Pro (Vals AI) | Not measured | 80.4% | Only o3 measured |
| GPQA Diamond (Artificial Analysis run) | 79.0% | 82.7% | o3 |
| Humanity's Last Exam (Artificial Analysis run) | 12.1% | 20.1% | o3 |
| GPQA Diamond (Epoch AI run) | Not measured | 81.8% | Only o3 measured |
| ARC-AGI | 33.3% | 60.8% | o3 |
| ARC-AGI-2 | 2.5% | 6.5% | o3 |
| SimpleBench | 41.2% | 53.1% | o3 |
| Chess puzzles | Not measured | 37.0% | Only o3 measured |
| Mystery game puzzles | Not measured | 29.0% | Only o3 measured |
| VPCT | Not measured | 52.0% | Only o3 measured |
| LMArena Text: hard prompts | 1422 | 1402 | Gemini 2.5 Flash |
| LMArena Text: expert | 1426 | 1402 | Gemini 2.5 Flash |
| LMArena Text: hard prompts in English | 1420 | 1411 | Gemini 2.5 Flash |
| LMArena Vision: diagrams | 1245 | 1220 | Gemini 2.5 Flash |
| LMArena Vision: homework | 1244 | 1234 | Gemini 2.5 Flash |
| Kagi LLM Benchmark | 56.8% | 67.6% | o3 |
| Neither model has a result on the other 5 boards here | |||
MathLike-for-likePublic boards, shown as published, kept out of the index04
| Benchmark | Gemini 2.5 Flash | o3 | Leader |
|---|---|---|---|
| AIME | Not measured | 85.3% | Only o3 measured |
| MATH 500 (Vals AI) | Not measured | 94.6% | Only o3 measured |
| MGSM (Vals AI) | Not measured | 91.8% | Only o3 measured |
| AA Math Index | 73.3 | 88.3 | o3 |
| AIME 2025 (Artificial Analysis run) | 73.3% | 88.3% | o3 |
| OTIS Mock AIME | Not measured | 84.4% | Only o3 measured |
| FrontierMath, tiers 1 to 3 | Not measured | 33.3% | Only o3 measured |
| MATH level 5 | Not measured | 97.8% | Only o3 measured |
| LMArena Text: math | 1411 | 1426 | o3 |
| LMArena Text: mathematical work | 1422 | 1423 | o3 |
| Neither model has a result on the other 3 boards here | |||
KnowledgeLike-for-likePublic boards, shown as published, kept out of the index43
| Benchmark | Gemini 2.5 Flash | o3 | Leader |
|---|---|---|---|
| MMLU Pro | Not measured | 85.6% | Only o3 measured |
| LegalBench (Vals AI) | Not measured | 83.8% | Only o3 measured |
| CorpFin (Vals AI) | Not measured | 59.7% | Only o3 measured |
| TaxEval (Vals AI) | Not measured | 74.6% | Only o3 measured |
| MortgageTax (Vals AI) | Not measured | 65.7% | Only o3 measured |
| MedQA (Vals AI) | Not measured | 96.1% | Only o3 measured |
| MedCode (Vals AI) | 40.4% | 47.3% | o3 |
| MMLU Pro (Artificial Analysis run) | 83.2% | 85.3% | o3 |
| SimpleQA Verified | Not measured | 49.4% | Only o3 measured |
| GeoBench | Not measured | 74.0% | Only o3 measured |
| LMArena Text: science | 1433 | 1429 | Gemini 2.5 Flash |
| LMArena Text: medicine and healthcare | 1428 | 1448 | o3 |
| LMArena Text: legal and government | 1430 | 1428 | Gemini 2.5 Flash |
| LMArena Text: business and finance | 1404 | 1393 | Gemini 2.5 Flash |
| FACTS Benchmark Suite | 47.2% | 44.4% | Gemini 2.5 Flash |
| Neither model has a result on the other 3 boards here | |||
Web designLike-for-likePublic boards, shown as published, kept out of the index23
| Benchmark | Gemini 2.5 Flash | o3 | Leader |
|---|---|---|---|
| Design Arena: websites | 1074 | 1036 | Gemini 2.5 Flash |
| Design Arena: UI components | 1002 | 1017 | o3 |
| Design Arena: game dev | 1004 | 1034 | o3 |
| Design Arena: data viz | 1060 | 1200 | o3 |
| Design Arena: 3D | 1020 | Not measured | Only Gemini 2.5 Flash measured |
| Design Arena: all code categories | 1059 | 1020 | Gemini 2.5 Flash |
| Design Arena: SVG | 1020 | Not measured | Only Gemini 2.5 Flash measured |
| Neither model has a result on the other 2 boards here | |||
GeneralLike-for-likePublic boards, shown as published, kept out of the index247
| Benchmark | Gemini 2.5 Flash | o3 | Leader |
|---|---|---|---|
| SAGE (Vals AI) | 44.8% | 41.8% | Gemini 2.5 Flash |
| MedScribe (Vals AI) | 83.0% | 76.7% | Gemini 2.5 Flash |
| IFBench | 50.3% | 71.4% | o3 |
| Long context reasoning (AA-LCR) | 65.3% | 74.7% | o3 |
| DTBench | 76.5% | 84.8% | o3 |
| LMCA | 27.5% | 39.7% | o3 |
| Fiction.LiveBench | Not measured | 88.9% | Only o3 measured |
| Creative writing (Lech Mazur) | Not measured | 83.9% | Only o3 measured |
| CL-bench | Not measured | 17.8% | Only o3 measured |
| LMArena Text | 1417 | 1410 | Gemini 2.5 Flash |
| LMArena Text: instruction following | 1405 | 1368 | Gemini 2.5 Flash |
| LMArena Text: creative writing | 1400 | 1359 | Gemini 2.5 Flash |
| LMArena Vision | 1235 | 1214 | Gemini 2.5 Flash |
| LMArena Text: English | 1418 | 1417 | Gemini 2.5 Flash |
| LMArena Text: non-English | 1409 | 1401 | Gemini 2.5 Flash |
| LMArena Text: Chinese | 1449 | 1437 | Gemini 2.5 Flash |
| LMArena Text: German | 1417 | 1420 | o3 |
| LMArena Text: Japanese | 1396 | 1403 | o3 |
| LMArena Text: Korean | 1385 | 1370 | Gemini 2.5 Flash |
| LMArena Text: French | 1432 | 1430 | Gemini 2.5 Flash |
| LMArena Text: Spanish | 1422 | 1395 | Gemini 2.5 Flash |
| LMArena Text: Russian | 1415 | 1406 | Gemini 2.5 Flash |
| LMArena Text: Polish | 1413 | 1438 | o3 |
| LMArena Text: multi-turn | 1408 | 1405 | Gemini 2.5 Flash |
| LMArena Text: longer queries | 1419 | 1372 | Gemini 2.5 Flash |
| LMArena Text: writing and language | 1405 | 1372 | Gemini 2.5 Flash |
| LMArena Text: entertainment and media | 1393 | 1373 | Gemini 2.5 Flash |
| LMArena Vision: English | 1239 | 1221 | Gemini 2.5 Flash |
| LMArena Vision: Chinese | 1284 | 1237 | Gemini 2.5 Flash |
| LMArena Vision: reading text | 1237 | 1218 | Gemini 2.5 Flash |
| LMArena Vision: humor | 1225 | 1222 | Gemini 2.5 Flash |
| LMArena Vision: captioning | 1277 | 1210 | Gemini 2.5 Flash |
| LMArena Vision: recognizing things | 1252 | 1234 | Gemini 2.5 Flash |
| LMArena Vision: creative writing | 1241 | 1201 | Gemini 2.5 Flash |
| Neither model has a result on the other 12 boards here | |||
Image generationNot comparablePublic boards, shown as published, kept out of the index0 boards, none shared
| Benchmark | Gemini 2.5 Flash | o3 | Leader |
|---|---|---|---|
| Neither model has a result on 5 boards here | |||
What each workload costs
Three fixed token mixes at each model's listed price, so per-token rates become a bill.
Chat turn
1K input + 500 output tokens
Gemini 2.5 Flash costs less
Repository review
50K input + 3K output tokens
Gemini 2.5 Flash costs less
Agent loop
200K input + 10K output tokens
Gemini 2.5 Flash costs less
Listed OpenRouter rates, without cache or batch discounts. A workload that does not fit a model's context window would need splitting.
Specification differences
The leading value in a row is marked; a row with a missing value names no leader. Our two rows are marked in red.
| Specification | Google Gemini 2.5 Flash | OpenAI o3 |
|---|---|---|
| Maker | OpenAI | |
| Weights | No public weights listed | No public weights listed |
| Released | June 17, 2025 | April 16, 2025 |
| Context window | 1.05M | 200K |
| Input $/Mtok | $0.30 | $2.00 |
| Output $/Mtok | $2.50 | $8.00 |
| Coding index | Not benchmarked | Not benchmarked |
| Independent measurements behind it | 0 | 0 |
| Cost per solved task | $0.466 | $0.571 |
| Source | OpenRouter listing | OpenRouter listing |
Questions
Is Gemini 2.5 Flash better than o3 for coding?
Neither model has a coding score yet, so the two cannot be ranked on coding. Pick Gemini 2.5 Flash for output tokens 3.2x cheaper ($2.50 vs $8.00 per million) and a lower cost per solved task ($0.466 against $0.571).
Which is cheaper, Gemini 2.5 Flash or o3?
Gemini 2.5 Flash costs $0.30 per million input tokens and $2.50 per million output tokens; o3 costs $2.00 and $8.00. Per solved SWE-bench Verified task, Gemini 2.5 Flash costs $0.466 and o3 $0.571.
Which has the bigger context window, Gemini 2.5 Flash or o3?
Gemini 2.5 Flash, with 1.05M tokens against 200K.
How many benchmarks is the Gemini 2.5 Flash vs o3 comparison based on?
68 benchmarks have a result for both models as of October 22, 2026. Gemini 2.5 Flash's coding index rests on 0 independent benchmarks and o3's on 0. Where only one model has a result, the page says so instead of naming a winner.