Claude Sonnet 4.5 vs Gemini 2.5 Flash
Claude Sonnet 4.5 leads Gemini 2.5 Flash on the Artificial Analysis Intelligence Index, 20.7 to 15.5, and Gemini 2.5 Flash costs 6.0x less per output token ($2.50 vs $15.00 per million). Updated October 22, 2026; 51 benchmarks have a result for both.
Claude Sonnet 4.5 or Gemini 2.5 Flash: which to pick
Only Claude Sonnet 4.5 has a coding score, 39.5 on the Vibe Coding Index; Gemini 2.5 Flash has none, so the two cannot be ranked on coding.
Pick Gemini 2.5 Flash for output tokens 6.0x cheaper ($2.50 vs $15.00 per million) and a lower cost per solved task ($0.466 against $1.16).
- Shared results
- 51
- Claude Sonnet 4.5 only
- 44
- Gemini 2.5 Flash only
- 22
- 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
Only Claude Sonnet 4.5 has a coding score, so no call is made.
One side not measured
Intelligence
AA Intelligence Index
Claude Sonnet 4.5
Claude Sonnet 4.5 leads, 20.7 against 15.5.
Same board, both measured
Agentic work
AA Agentic Index
No call
Only Claude Sonnet 4.5 has a AA Agentic Index result, 15.8.
Directional only
Reasoning
GPQA Diamond
No call
Only Claude Sonnet 4.5 has a GPQA Diamond result, 81.6%.
Directional only
Math
AIME
No call
Only Claude Sonnet 4.5 has a AIME result, 88.2%.
Directional only
Knowledge
MMLU Pro
No call
Only Claude Sonnet 4.5 has a MMLU Pro result, 87.4%.
Directional only
Web design
Design Arena: websites
Claude Sonnet 4.5
Claude Sonnet 4.5 leads, 1189 against 1074.
Same board, both measured
Long documents
Listed context window
Gemini 2.5 Flash
Gemini 2.5 Flash takes 1.05M tokens against 1M.
Listed by OpenRouter
Everyday cost
1K input + 500 output tokens
Gemini 2.5 Flash
Claude Sonnet 4.5 $0.011, Gemini 2.5 Flash $0.0015 per turn.
List prices
Cost per solved task
One SWE-bench Verified task, solved
Gemini 2.5 Flash
Claude Sonnet 4.5 $1.16, Gemini 2.5 Flash $0.466.
Published attempt cost and pass rate
At a glance
- Coding index
- Claude Sonnet 4.5 39.5 from 3 benchmarks, Gemini 2.5 Flash not benchmarked.
- Widest category
- Coding, 23.6 points apart on average over 4 shared benchmarks.
- Widest single gap
- SWE-bench Verified: Claude Sonnet 4.5 74.8% against Gemini 2.5 Flash 28.7%, 46.1 points apart on a 0 to 100 scale.
- Output price
- Claude Sonnet 4.5 $15.00 against Gemini 2.5 Flash $2.50 per million output tokens, 6.0x apart.
- Context window
- Claude Sonnet 4.5 takes 1M tokens, Gemini 2.5 Flash 1.05M.
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 | Claude Sonnet 4.5 | Bars | Gemini 2.5 Flash | Ties |
|---|---|---|---|---|
| Coding | 4 | 0 | ||
| Intelligence | 2 | 0 | ||
| Agentic work | 2 | 0 | ||
| Reasoning | 7 | 0 | ||
| Math | 2 | 0 | ||
| Knowledge | 5 | 1 | ||
| Web design | 7 | 0 | ||
| General | 19 | 2 | ||
| All shared boards | 48 | 3 |
CodingLike-for-likeSix of these boards feed the Vibe Coding Index40
| Benchmark | Claude Sonnet 4.5 | Gemini 2.5 Flash | Leader |
|---|---|---|---|
| SWE-bench Verified | 74.8% | 28.7% | Claude Sonnet 4.5 |
| SWE-bench Multilingual | 67.0% | Not measured | Only Claude Sonnet 4.5 measured |
| LMArena WebDev | 1394 | Not measured | Only Claude Sonnet 4.5 measured |
| AA Coding Index | 52.1 | Not measured | Only Claude Sonnet 4.5 measured |
| LiveCodeBench (Vals AI) | 73.0% | Not measured | Only Claude Sonnet 4.5 measured |
| SWE-bench Verified (Vals AI) | 70.0% | Not measured | Only Claude Sonnet 4.5 measured |
| Vibe Code Bench (Vals AI) | 22.6% | Not measured | Only Claude Sonnet 4.5 measured |
| LiveCodeBench (Artificial Analysis run) | Not measured | 69.5% | Only Gemini 2.5 Flash measured |
| Terminal-Bench Hard (Artificial Analysis run) | Not measured | 13.6% | Only Gemini 2.5 Flash measured |
| Terminal-Bench | 46.5% | 17.1% | Claude Sonnet 4.5 |
| GSO-Bench | 14.7% | Not measured | Only Claude Sonnet 4.5 measured |
| WeirdML | 47.7% | Not measured | Only Claude Sonnet 4.5 measured |
| Cybench | 60.0% | Not measured | Only Claude Sonnet 4.5 measured |
| LMArena Text: coding | 1488 | 1423 | Claude Sonnet 4.5 |
| LMArena Text: software and IT | 1473 | 1425 | Claude Sonnet 4.5 |
| LMArena WebDev: React | 1386 | Not measured | Only Claude Sonnet 4.5 measured |
| LMArena WebDev: HTML | 1399 | Not measured | Only Claude Sonnet 4.5 measured |
| Neither model has a result on the other 22 boards here | |||
IntelligenceLike-for-likePublic boards, shown as published, kept out of the index20
| Benchmark | Claude Sonnet 4.5 | Gemini 2.5 Flash | Leader |
|---|---|---|---|
| AA Intelligence Index | 20.7 | 15.5 | Claude Sonnet 4.5 |
| Epoch Capabilities Index | 146.7 | 142.9 | Claude Sonnet 4.5 |
Agentic workLike-for-likePublic boards, shown as published, kept out of the index20
| Benchmark | Claude Sonnet 4.5 | Gemini 2.5 Flash | Leader |
|---|---|---|---|
| AA Agentic Index | 15.8 | Not measured | Only Claude Sonnet 4.5 measured |
| Design Arena: agents building web apps | 1060 | Not measured | Only Claude Sonnet 4.5 measured |
| Design Arena: agents building full-stack apps | 1050 | Not measured | Only Claude Sonnet 4.5 measured |
| Design Arena: agents building mobile apps | 1137 | Not measured | Only Claude Sonnet 4.5 measured |
| τ²-Bench Telecom | Not measured | 31.6% | Only Gemini 2.5 Flash measured |
| METR time horizons | 67.4% | Not measured | Only Claude Sonnet 4.5 measured |
| Remote Labor Index | 2.1% | Not measured | Only Claude Sonnet 4.5 measured |
| GDPval | 42.5% | Not measured | Only Claude Sonnet 4.5 measured |
| BALROG | Not measured | 33.5% | Only Gemini 2.5 Flash measured |
| DeepResearch Bench | 52.6% | Not measured | Only Claude Sonnet 4.5 measured |
| OSWorld | 62.9% | Not measured | Only Claude Sonnet 4.5 measured |
| Vending-Bench 2 | $3,839 | $549 | Claude Sonnet 4.5 |
| Berkeley Function Calling Leaderboard (BFCL) | 73.2% | 56.2% | Claude Sonnet 4.5 |
| BrowseComp-Plus | Not measured | 39.9% | Only Gemini 2.5 Flash measured |
| Neither model has a result on the other 27 boards here | |||
ReasoningLike-for-likePublic boards, shown as published, kept out of the index70
| Benchmark | Claude Sonnet 4.5 | Gemini 2.5 Flash | Leader |
|---|---|---|---|
| GPQA Diamond | 81.6% | Not measured | Only Claude Sonnet 4.5 measured |
| MMMU Pro (Vals AI) | 79.3% | Not measured | Only Claude Sonnet 4.5 measured |
| GPQA Diamond (Artificial Analysis run) | Not measured | 79.0% | Only Gemini 2.5 Flash measured |
| Humanity's Last Exam (Artificial Analysis run) | Not measured | 12.1% | Only Gemini 2.5 Flash measured |
| GPQA Diamond (Epoch AI run) | 82.3% | Not measured | Only Claude Sonnet 4.5 measured |
| ARC-AGI | 63.7% | 33.3% | Claude Sonnet 4.5 |
| ARC-AGI-2 | 13.6% | 2.5% | Claude Sonnet 4.5 |
| SimpleBench | 54.3% | 41.2% | Claude Sonnet 4.5 |
| Chess puzzles | 10.0% | Not measured | Only Claude Sonnet 4.5 measured |
| Mystery game puzzles | 17.0% | Not measured | Only Claude Sonnet 4.5 measured |
| EBR-bench | 2.4% | Not measured | Only Claude Sonnet 4.5 measured |
| VPCT | 39.8% | Not measured | Only Claude Sonnet 4.5 measured |
| LMArena Text: hard prompts | 1462 | 1422 | Claude Sonnet 4.5 |
| LMArena Text: expert | 1483 | 1426 | Claude Sonnet 4.5 |
| LMArena Text: hard prompts in English | 1471 | 1420 | Claude Sonnet 4.5 |
| LMArena Vision: diagrams | Not measured | 1245 | Only Gemini 2.5 Flash measured |
| LMArena Vision: homework | Not measured | 1244 | Only Gemini 2.5 Flash measured |
| Kagi LLM Benchmark | 57.9% | 56.8% | Claude Sonnet 4.5 |
| Neither model has a result on the other 4 boards here | |||
MathLike-for-likePublic boards, shown as published, kept out of the index20
| Benchmark | Claude Sonnet 4.5 | Gemini 2.5 Flash | Leader |
|---|---|---|---|
| AIME | 88.2% | Not measured | Only Claude Sonnet 4.5 measured |
| MGSM (Vals AI) | 94.3% | Not measured | Only Claude Sonnet 4.5 measured |
| AA Math Index | Not measured | 73.3 | Only Gemini 2.5 Flash measured |
| AIME 2025 (Artificial Analysis run) | Not measured | 73.3% | Only Gemini 2.5 Flash measured |
| OTIS Mock AIME | 77.8% | Not measured | Only Claude Sonnet 4.5 measured |
| FrontierMath, tiers 1 to 3 | 23.9% | Not measured | Only Claude Sonnet 4.5 measured |
| FrontierMath, tier 4 | 2.4% | Not measured | Only Claude Sonnet 4.5 measured |
| ProofBench | 19.0% | Not measured | Only Claude Sonnet 4.5 measured |
| MATH level 5 | 97.7% | Not measured | Only Claude Sonnet 4.5 measured |
| LMArena Text: math | 1449 | 1411 | Claude Sonnet 4.5 |
| LMArena Text: mathematical work | 1462 | 1422 | Claude Sonnet 4.5 |
| Neither model has a result on the other 2 boards here | |||
KnowledgeLike-for-likePublic boards, shown as published, kept out of the index51
| Benchmark | Claude Sonnet 4.5 | Gemini 2.5 Flash | Leader |
|---|---|---|---|
| MMLU Pro | 87.4% | Not measured | Only Claude Sonnet 4.5 measured |
| LegalBench (Vals AI) | 84.1% | Not measured | Only Claude Sonnet 4.5 measured |
| CaseLaw (Vals AI) | 62.2% | Not measured | Only Claude Sonnet 4.5 measured |
| CorpFin (Vals AI) | 62.0% | Not measured | Only Claude Sonnet 4.5 measured |
| TaxEval (Vals AI) | 73.3% | Not measured | Only Claude Sonnet 4.5 measured |
| MortgageTax (Vals AI) | 64.0% | Not measured | Only Claude Sonnet 4.5 measured |
| MedQA (Vals AI) | 94.7% | Not measured | Only Claude Sonnet 4.5 measured |
| MedCode (Vals AI) | 44.1% | 40.4% | Claude Sonnet 4.5 |
| MMLU Pro (Artificial Analysis run) | Not measured | 83.2% | Only Gemini 2.5 Flash measured |
| SimpleQA Verified | 30.7% | Not measured | Only Claude Sonnet 4.5 measured |
| LMArena Text: science | 1448 | 1433 | Claude Sonnet 4.5 |
| LMArena Text: medicine and healthcare | 1444 | 1428 | Claude Sonnet 4.5 |
| LMArena Text: legal and government | 1451 | 1430 | Claude Sonnet 4.5 |
| LMArena Text: business and finance | 1440 | 1404 | Claude Sonnet 4.5 |
| FACTS Benchmark Suite | 40.6% | 47.2% | 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 index70
| Benchmark | Claude Sonnet 4.5 | Gemini 2.5 Flash | Leader |
|---|---|---|---|
| Design Arena: websites | 1189 | 1074 | Claude Sonnet 4.5 |
| Design Arena: UI components | 1170 | 1002 | Claude Sonnet 4.5 |
| Design Arena: game dev | 1166 | 1004 | Claude Sonnet 4.5 |
| Design Arena: data viz | 1167 | 1060 | Claude Sonnet 4.5 |
| Design Arena: 3D | 1157 | 1020 | Claude Sonnet 4.5 |
| Design Arena: all code categories | 1182 | 1059 | Claude Sonnet 4.5 |
| Design Arena: SVG | 1115 | 1020 | Claude Sonnet 4.5 |
| Design Arena: ASCII art | 1205 | Not measured | Only Claude Sonnet 4.5 measured |
| Neither model has a result on the other 1 board here | |||
GeneralLike-for-likePublic boards, shown as published, kept out of the index192
| Benchmark | Claude Sonnet 4.5 | Gemini 2.5 Flash | Leader |
|---|---|---|---|
| SAGE (Vals AI) | 36.1% | 44.8% | Gemini 2.5 Flash |
| MedScribe (Vals AI) | 84.5% | 83.0% | Claude Sonnet 4.5 |
| IFBench | Not measured | 50.3% | Only Gemini 2.5 Flash measured |
| Long context reasoning (AA-LCR) | Not measured | 65.3% | Only Gemini 2.5 Flash measured |
| DTBench | 83.2% | 76.5% | Claude Sonnet 4.5 |
| LMCA | 38.8% | 27.5% | Claude Sonnet 4.5 |
| LMArena Text | 1438 | 1417 | Claude Sonnet 4.5 |
| LMArena Text: instruction following | 1459 | 1405 | Claude Sonnet 4.5 |
| LMArena Text: creative writing | 1442 | 1400 | Claude Sonnet 4.5 |
| LMArena Vision | Not measured | 1235 | Only Gemini 2.5 Flash measured |
| LMArena Text: English | 1450 | 1418 | Claude Sonnet 4.5 |
| LMArena Text: non-English | 1425 | 1409 | Claude Sonnet 4.5 |
| LMArena Text: Chinese | 1460 | 1449 | Claude Sonnet 4.5 |
| LMArena Text: German | 1427 | 1417 | Claude Sonnet 4.5 |
| LMArena Text: Japanese | 1390 | 1396 | Gemini 2.5 Flash |
| LMArena Text: Korean | 1402 | 1385 | Claude Sonnet 4.5 |
| LMArena Text: French | 1459 | 1432 | Claude Sonnet 4.5 |
| LMArena Text: Spanish | 1458 | 1422 | Claude Sonnet 4.5 |
| LMArena Text: Russian | 1437 | 1415 | Claude Sonnet 4.5 |
| LMArena Text: Polish | 1423 | 1413 | Claude Sonnet 4.5 |
| LMArena Text: multi-turn | 1465 | 1408 | Claude Sonnet 4.5 |
| LMArena Text: longer queries | 1475 | 1419 | Claude Sonnet 4.5 |
| LMArena Text: writing and language | 1442 | 1405 | Claude Sonnet 4.5 |
| LMArena Text: entertainment and media | 1428 | 1393 | Claude Sonnet 4.5 |
| LMArena Vision: English | Not measured | 1239 | Only Gemini 2.5 Flash measured |
| LMArena Vision: Chinese | Not measured | 1284 | Only Gemini 2.5 Flash measured |
| LMArena Vision: reading text | Not measured | 1237 | Only Gemini 2.5 Flash measured |
| LMArena Vision: humor | Not measured | 1225 | Only Gemini 2.5 Flash measured |
| LMArena Vision: captioning | Not measured | 1277 | Only Gemini 2.5 Flash measured |
| LMArena Vision: recognizing things | Not measured | 1252 | Only Gemini 2.5 Flash measured |
| LMArena Vision: creative writing | Not measured | 1241 | Only Gemini 2.5 Flash measured |
| LMArena Document | 1450 | Not measured | Only Claude Sonnet 4.5 measured |
| Neither model has a result on the other 14 boards here | |||
Image generationNot comparablePublic boards, shown as published, kept out of the index0 boards, none shared
| Benchmark | Claude Sonnet 4.5 | Gemini 2.5 Flash | 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 | Anthropic Claude Sonnet 4.5 | Google Gemini 2.5 Flash |
|---|---|---|
| Maker | Anthropic | |
| Weights | No public weights listed | No public weights listed |
| Released | September 29, 2025 | June 17, 2025 |
| Context window | 1M | 1.05M |
| Input $/Mtok | $3.00 | $0.30 |
| Output $/Mtok | $15.00 | $2.50 |
| Coding index | 39.5 | Not benchmarked |
| Independent measurements behind it | 3 | 0 |
| Cost per solved task | $1.16 | $0.466 |
| Source | OpenRouter listing | OpenRouter listing |
Questions
Is Claude Sonnet 4.5 better than Gemini 2.5 Flash for coding?
Only Claude Sonnet 4.5 has a coding score, 39.5 on the Vibe Coding Index; Gemini 2.5 Flash has none, so the two cannot be ranked on coding. Pick Gemini 2.5 Flash for output tokens 6.0x cheaper ($2.50 vs $15.00 per million) and a lower cost per solved task ($0.466 against $1.16).
Which is cheaper, Claude Sonnet 4.5 or Gemini 2.5 Flash?
Claude Sonnet 4.5 costs $3.00 per million input tokens and $15.00 per million output tokens; Gemini 2.5 Flash costs $0.30 and $2.50. Per solved SWE-bench Verified task, Claude Sonnet 4.5 costs $1.16 and Gemini 2.5 Flash $0.466.
Which has the bigger context window, Claude Sonnet 4.5 or Gemini 2.5 Flash?
Gemini 2.5 Flash, with 1.05M tokens against 1M.
How many benchmarks is the Claude Sonnet 4.5 vs Gemini 2.5 Flash comparison based on?
51 benchmarks have a result for both models as of October 22, 2026. Claude Sonnet 4.5's coding index rests on 3 independent benchmarks and Gemini 2.5 Flash's on 0. Where only one model has a result, the page says so instead of naming a winner.