Claude Sonnet 5.5 vs gpt-oss-20b
Claude Sonnet 5.5 leads gpt-oss-20b on the Artificial Analysis Intelligence Index, 56.0 to 10.0, and gpt-oss-20b costs 66.7x less per output token ($0.15 vs $10.00 per million). Updated October 21, 2026; 35 benchmarks have a result for both.
vs boards won of 35 shared
Claude Sonnet 5.5 or gpt-oss-20b: which to pick
Only Claude Sonnet 5.5 has a coding score, 87.3 on the Vibe Coding Index; gpt-oss-20b has none, so the two cannot be ranked on coding.
Pick gpt-oss-20b for output tokens 66.7x cheaper ($0.15 vs $10.00 per million).
Model AClaude Sonnet 5.5Anthropic87.3/1005 independent benchmarksNo cost per solved taskModel Bgpt-oss-20bOpenAINot benchmarkedNo coding benchmarkNo cost per solved task
- Shared results
- 35
- Claude Sonnet 5.5 only
- 61
- gpt-oss-20b only
- 27
- Like-for-like categories
- 7 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 5.5 has a coding score, so no call is made.
One side not measured
Intelligence
AA Intelligence Index
Claude Sonnet 5.5
Claude Sonnet 5.5 leads, 56.0 against 10.0.
Same board, both measured
Reasoning
GPQA Diamond
No call
Only gpt-oss-20b has a GPQA Diamond result, 68.9%.
Directional only
Math
AIME
No call
Only gpt-oss-20b has a AIME result, 86.0%.
Directional only
Knowledge
MMLU Pro
No call
Only gpt-oss-20b has a MMLU Pro result, 71.6%.
Directional only
Web design
Design Arena: websites
Claude Sonnet 5.5
Claude Sonnet 5.5 leads, 1326 against 852.
Same board, both measured
General
Vals Index
No call
Only Claude Sonnet 5.5 has a Vals Index result, 70.8%.
Directional only
Long documents
Listed context window
Claude Sonnet 5.5
Claude Sonnet 5.5 takes 1M tokens against 131K.
Listed by OpenRouter
Everyday cost
1K input + 500 output tokens
gpt-oss-20b
Claude Sonnet 5.5 $0.0070, gpt-oss-20b $0.0001 per turn.
List prices
At a glance
- Coding index
- Claude Sonnet 5.5 87.3 from 5 benchmarks, gpt-oss-20b not benchmarked.
- Widest category
- Web design, 58.4 points apart on average over 2 shared benchmarks.
- Widest single gap
- Design Arena: websites: Claude Sonnet 5.5 1326 against gpt-oss-20b 852, 59.3 points apart on a 0 to 100 scale.
- Output price
- Claude Sonnet 5.5 $10.00 against gpt-oss-20b $0.15 per million output tokens, 66.7x apart.
- Context window
- Claude Sonnet 5.5 takes 1M tokens, gpt-oss-20b 131K.
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 5.5 | Bars | gpt-oss-20b | Ties |
|---|---|---|---|---|
| Coding | 4 | 0 | ||
| Intelligence | 2 | 0 | ||
| Reasoning | 5 | 0 | ||
| Math | 3 | 0 | ||
| Knowledge | 4 | 0 | ||
| Web design | 2 | 0 | ||
| General | 15 | 0 | ||
| All shared boards | 35 | 0 |
CodingLike-for-likeSix of these boards feed the Vibe Coding Index40
| Benchmark | Claude Sonnet 5.5 | gpt-oss-20b | Leader |
|---|---|---|---|
| LiveBench coding | 94.7% | Not measured | Only Claude Sonnet 5.5 measured |
| LMArena WebDev | 1768 | Not measured | Only Claude Sonnet 5.5 measured |
| LiveCodeBench (Vals AI) | Not measured | 80.4% | Only gpt-oss-20b measured |
| Terminal-Bench 4 (Vals AI) | 64.1% | Not measured | Only Claude Sonnet 5.5 measured |
| Vibe Code Bench (Vals AI) | 92.4% | Not measured | Only Claude Sonnet 5.5 measured |
| Code migration (Vals AI) | 69.8% | Not measured | Only Claude Sonnet 5.5 measured |
| ProgramBench (Vals AI) | 6.5% | Not measured | Only Claude Sonnet 5.5 measured |
| IOI (Vals AI) | 83.1% | Not measured | Only Claude Sonnet 5.5 measured |
| Terminal-Bench 2.1 (Vals AI) | 83.2% | Not measured | Only Claude Sonnet 5.5 measured |
| SWE-bench Multimodal (Vals AI) | 58.3% | Not measured | Only Claude Sonnet 5.5 measured |
| CyberBench (Vals AI) | 59.6% | Not measured | Only Claude Sonnet 5.5 measured |
| LiveCodeBench (Artificial Analysis run) | Not measured | 77.7% | Only gpt-oss-20b measured |
| SciCode | 61.0% | 38.9% | Claude Sonnet 5.5 |
| Terminal-Bench Hard (Artificial Analysis run) | Not measured | 10.6% | Only gpt-oss-20b measured |
| Terminal-Bench | Not measured | 3.4% | Only gpt-oss-20b measured |
| FrontierCode | 52.1% | Not measured | Only Claude Sonnet 5.5 measured |
| FrontierSWE | 61.9% | Not measured | Only Claude Sonnet 5.5 measured |
| WeirdML | Not measured | 40.9% | Only gpt-oss-20b measured |
| ALE-Bench | 1819.1 | 566.0 | Claude Sonnet 5.5 |
| LMArena Text: coding | 1513 | 1307 | Claude Sonnet 5.5 |
| LMArena Text: software and IT | 1504 | 1311 | Claude Sonnet 5.5 |
| LMArena WebDev: React | 1817 | Not measured | Only Claude Sonnet 5.5 measured |
| LMArena WebDev: HTML | 1741 | Not measured | Only Claude Sonnet 5.5 measured |
| LMArena WebDev: from an image | 1737 | Not measured | Only Claude Sonnet 5.5 measured |
| SciCode | 13.8% | Not measured | Only Claude Sonnet 5.5 measured |
| Neither model has a result on the other 14 boards here | |||
IntelligenceLike-for-likePublic boards, shown as published, kept out of the index20
| Benchmark | Claude Sonnet 5.5 | gpt-oss-20b | Leader |
|---|---|---|---|
| AA Intelligence Index | 56.0 | 10.0 | Claude Sonnet 5.5 |
| Epoch Capabilities Index | 166.2 | 137.7 | Claude Sonnet 5.5 |
Agentic workDirectional onlyPublic boards, shown as published, kept out of the index20 boards, none shared
| Benchmark | Claude Sonnet 5.5 | gpt-oss-20b | Leader |
|---|---|---|---|
| Design Arena: agents building web apps | 1306 | Not measured | Only Claude Sonnet 5.5 measured |
| Design Arena: agents building mobile apps | 1257 | Not measured | Only Claude Sonnet 5.5 measured |
| Design Arena: spreadsheets | 1244 | Not measured | Only Claude Sonnet 5.5 measured |
| LiveBench research | 83.6% | Not measured | Only Claude Sonnet 5.5 measured |
| LiveBench browser | 84.0% | Not measured | Only Claude Sonnet 5.5 measured |
| LiveBench long agentic | 78.8% | Not measured | Only Claude Sonnet 5.5 measured |
| SREBench (Vals AI) | 30.1% | Not measured | Only Claude Sonnet 5.5 measured |
| Finance Agent (Vals AI) | 58.1% | Not measured | Only Claude Sonnet 5.5 measured |
| Tax Agent Bench (Vals AI) | 42.0% | Not measured | Only Claude Sonnet 5.5 measured |
| Legal Research Bench (Vals AI) | 48.1% | Not measured | Only Claude Sonnet 5.5 measured |
| Harvey's Legal Agent Benchmark (Vals AI) | 10.4% | Not measured | Only Claude Sonnet 5.5 measured |
| Excel Modeling Benchmark (Vals AI) | 75.7% | Not measured | Only Claude Sonnet 5.5 measured |
| BioMysteryBench (Vals AI) | 81.1% | Not measured | Only Claude Sonnet 5.5 measured |
| Terminal-Bench-Science (Vals AI) | 47.1% | Not measured | Only Claude Sonnet 5.5 measured |
| Vals Science Index | 59.1% | Not measured | Only Claude Sonnet 5.5 measured |
| τ²-Bench Telecom | Not measured | 60.2% | Only gpt-oss-20b measured |
| APEX-Agents | 75.5% | Not measured | Only Claude Sonnet 5.5 measured |
| SpireClimb | 1.3% | Not measured | Only Claude Sonnet 5.5 measured |
| Vending-Bench 2 | $11,165 | Not measured | Only Claude Sonnet 5.5 measured |
| BrowseComp-Plus | Not measured | 50.6% | Only gpt-oss-20b measured |
| Neither model has a result on the other 21 boards here | |||
ReasoningLike-for-likePublic boards, shown as published, kept out of the index50
| Benchmark | Claude Sonnet 5.5 | gpt-oss-20b | Leader |
|---|---|---|---|
| GPQA Diamond | Not measured | 68.9% | Only gpt-oss-20b measured |
| LiveBench reasoning | 91.6% | Not measured | Only Claude Sonnet 5.5 measured |
| MysteryMechanism (Vals AI) | 49.1% | Not measured | Only Claude Sonnet 5.5 measured |
| GPQA Diamond (Artificial Analysis run) | Not measured | 68.8% | Only gpt-oss-20b measured |
| Humanity's Last Exam (Artificial Analysis run) | 55.0% | 11.0% | Claude Sonnet 5.5 |
| GPQA Diamond (Epoch AI run) | 95.6% | 60.8% | Claude Sonnet 5.5 |
| Chess puzzles | 59.0% | Not measured | Only Claude Sonnet 5.5 measured |
| Mystery game puzzles | 65.0% | Not measured | Only Claude Sonnet 5.5 measured |
| LMArena Text: hard prompts | 1494 | 1274 | Claude Sonnet 5.5 |
| LMArena Text: expert | 1531 | 1258 | Claude Sonnet 5.5 |
| LMArena Text: hard prompts in English | 1502 | 1292 | Claude Sonnet 5.5 |
| LMArena Vision: diagrams | 1329 | Not measured | Only Claude Sonnet 5.5 measured |
| LMArena Vision: homework | 1331 | Not measured | Only Claude Sonnet 5.5 measured |
| Kagi LLM Benchmark | Not measured | 53.2% | Only gpt-oss-20b measured |
| Neither model has a result on the other 8 boards here | |||
MathLike-for-likePublic boards, shown as published, kept out of the index30
| Benchmark | Claude Sonnet 5.5 | gpt-oss-20b | Leader |
|---|---|---|---|
| AIME | Not measured | 86.0% | Only gpt-oss-20b measured |
| MATH 500 (Vals AI) | Not measured | 94.2% | Only gpt-oss-20b measured |
| MGSM (Vals AI) | Not measured | 89.0% | Only gpt-oss-20b measured |
| AA Math Index | Not measured | 89.3 | Only gpt-oss-20b measured |
| AIME 2025 (Artificial Analysis run) | Not measured | 89.3% | Only gpt-oss-20b measured |
| OTIS Mock AIME | 100.0% | 65.3% | Claude Sonnet 5.5 |
| FrontierMath, tiers 1 to 3 | 88.8% | Not measured | Only Claude Sonnet 5.5 measured |
| FrontierMath, tier 4 | 80.5% | Not measured | Only Claude Sonnet 5.5 measured |
| ProofBench | 100.0% | Not measured | Only Claude Sonnet 5.5 measured |
| LMArena Text: math | 1497 | 1317 | Claude Sonnet 5.5 |
| LMArena Text: mathematical work | 1510 | 1305 | Claude Sonnet 5.5 |
| Neither model has a result on the other 2 boards here | |||
KnowledgeLike-for-likePublic boards, shown as published, kept out of the index40
| Benchmark | Claude Sonnet 5.5 | gpt-oss-20b | Leader |
|---|---|---|---|
| MMLU Pro | Not measured | 71.6% | Only gpt-oss-20b measured |
| LegalBench (Vals AI) | Not measured | 70.8% | Only gpt-oss-20b measured |
| CaseLaw (Vals AI) | Not measured | 43.8% | Only gpt-oss-20b measured |
| CorpFin (Vals AI) | Not measured | 53.1% | Only gpt-oss-20b measured |
| TaxEval (Vals AI) | Not measured | 63.7% | Only gpt-oss-20b measured |
| MedQA (Vals AI) | Not measured | 82.9% | Only gpt-oss-20b measured |
| MedCode (Vals AI) | 52.9% | Not measured | Only Claude Sonnet 5.5 measured |
| MMLU Pro (Artificial Analysis run) | Not measured | 74.8% | Only gpt-oss-20b measured |
| SimpleQA Verified | 46.5% | Not measured | Only Claude Sonnet 5.5 measured |
| LMArena Text: science | 1483 | 1296 | Claude Sonnet 5.5 |
| LMArena Text: medicine and healthcare | 1464 | 1310 | Claude Sonnet 5.5 |
| LMArena Text: legal and government | 1483 | 1280 | Claude Sonnet 5.5 |
| LMArena Text: business and finance | 1468 | 1284 | Claude Sonnet 5.5 |
| Neither model has a result on the other 5 boards here | |||
Web designLike-for-likePublic boards, shown as published, kept out of the index20
| Benchmark | Claude Sonnet 5.5 | gpt-oss-20b | Leader |
|---|---|---|---|
| Design Arena: websites | 1326 | 852 | Claude Sonnet 5.5 |
| Design Arena: UI components | 1365 | Not measured | Only Claude Sonnet 5.5 measured |
| Design Arena: game dev | 1469 | Not measured | Only Claude Sonnet 5.5 measured |
| Design Arena: data viz | 1394 | 933 | Claude Sonnet 5.5 |
| Design Arena: 3D | 1452 | Not measured | Only Claude Sonnet 5.5 measured |
| Design Arena: all code categories | 1364 | Not measured | Only Claude Sonnet 5.5 measured |
| LiveBench design | 85.0% | Not measured | Only Claude Sonnet 5.5 measured |
| Neither model has a result on the other 2 boards here | |||
GeneralLike-for-likePublic boards, shown as published, kept out of the index150
| Benchmark | Claude Sonnet 5.5 | gpt-oss-20b | Leader |
|---|---|---|---|
| Vals Index | 70.8% | Not measured | Only Claude Sonnet 5.5 measured |
| LiveBench data analysis | 59.5% | Not measured | Only Claude Sonnet 5.5 measured |
| Public Benefits Bench (Vals AI) | 67.2% | Not measured | Only Claude Sonnet 5.5 measured |
| SAGE (Vals AI) | 51.8% | Not measured | Only Claude Sonnet 5.5 measured |
| MedScribe (Vals AI) | 91.1% | Not measured | Only Claude Sonnet 5.5 measured |
| IFBench | Not measured | 65.1% | Only gpt-oss-20b measured |
| Long context reasoning (AA-LCR) | 82.7% | 34.7% | Claude Sonnet 5.5 |
| DTBench | 97.3% | 68.0% | Claude Sonnet 5.5 |
| LMCA | 68.3% | 14.5% | Claude Sonnet 5.5 |
| Furniture assembly | 75.0% | Not measured | Only Claude Sonnet 5.5 measured |
| LMArena Text | 1473 | 1288 | Claude Sonnet 5.5 |
| LMArena Text: instruction following | 1492 | 1236 | Claude Sonnet 5.5 |
| LMArena Text: creative writing | 1467 | 1201 | Claude Sonnet 5.5 |
| LMArena Vision | 1287 | Not measured | Only Claude Sonnet 5.5 measured |
| LMArena Text: English | 1484 | 1303 | Claude Sonnet 5.5 |
| LMArena Text: non-English | 1456 | 1269 | Claude Sonnet 5.5 |
| LMArena Text: Chinese | 1535 | 1315 | Claude Sonnet 5.5 |
| LMArena Text: German | Not measured | 1255 | Only gpt-oss-20b measured |
| LMArena Text: Japanese | Not measured | 1244 | Only gpt-oss-20b measured |
| LMArena Text: Korean | Not measured | 1236 | Only gpt-oss-20b measured |
| LMArena Text: French | 1499 | Not measured | Only Claude Sonnet 5.5 measured |
| LMArena Text: Spanish | 1451 | 1267 | Claude Sonnet 5.5 |
| LMArena Text: Russian | 1454 | 1278 | Claude Sonnet 5.5 |
| LMArena Text: Polish | Not measured | 1252 | Only gpt-oss-20b measured |
| LMArena Text: multi-turn | 1465 | 1268 | Claude Sonnet 5.5 |
| LMArena Text: longer queries | 1495 | 1250 | Claude Sonnet 5.5 |
| LMArena Text: writing and language | 1474 | 1238 | Claude Sonnet 5.5 |
| LMArena Text: entertainment and media | 1461 | 1216 | Claude Sonnet 5.5 |
| LMArena Vision: English | 1289 | Not measured | Only Claude Sonnet 5.5 measured |
| LMArena Vision: reading text | 1297 | Not measured | Only Claude Sonnet 5.5 measured |
| LMArena Vision: creative writing | 1242 | Not measured | Only Claude Sonnet 5.5 measured |
| Neither model has a result on the other 15 boards here | |||
Image generationNot comparablePublic boards, shown as published, kept out of the index0 boards, none shared
| Benchmark | Claude Sonnet 5.5 | gpt-oss-20b | 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
Claude Sonnet 5.5$0.0070Fits in one request
gpt-oss-20b$0.0001Fits in one request
gpt-oss-20b costs less
Repository review
50K input + 3K output tokens
Claude Sonnet 5.5$0.130Fits in one request
gpt-oss-20b$0.0019Fits in one request
gpt-oss-20b costs less
Agent loop
200K input + 10K output tokens
Claude Sonnet 5.5$0.500Fits in one request
gpt-oss-20b$0.0075Exceeds the context window
gpt-oss-20b 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 5.5 | OpenAI gpt-oss-20b |
|---|---|---|
| Maker | Anthropic | OpenAI |
| Weights | No public weights listed | Open weights |
| Released | September 28, 2026 | August 5, 2025 |
| Context window | 1M | 131K |
| Input $/Mtok | $2.00 | $0.03 |
| Output $/Mtok | $10.00 | $0.15 |
| Coding index | 87.3 | Not benchmarked |
| Independent measurements behind it | 5 | 0 |
| Cost per solved task | Not computable | Not computable |
| Source | OpenRouter listing | OpenRouter listing |
Questions
Is Claude Sonnet 5.5 better than gpt-oss-20b for coding?
Only Claude Sonnet 5.5 has a coding score, 87.3 on the Vibe Coding Index; gpt-oss-20b has none, so the two cannot be ranked on coding. Pick gpt-oss-20b for output tokens 66.7x cheaper ($0.15 vs $10.00 per million).
Which is cheaper, Claude Sonnet 5.5 or gpt-oss-20b?
Claude Sonnet 5.5 costs $2.00 per million input tokens and $10.00 per million output tokens; gpt-oss-20b costs $0.03 and $0.15. Cost per solved task is known for neither of them.
Which has the bigger context window, Claude Sonnet 5.5 or gpt-oss-20b?
Claude Sonnet 5.5, with 1M tokens against 131K.
How many benchmarks is the Claude Sonnet 5.5 vs gpt-oss-20b comparison based on?
35 benchmarks have a result for both models as of October 21, 2026. Claude Sonnet 5.5's coding index rests on 5 independent benchmarks and gpt-oss-20b's on 0. Where only one model has a result, the page says so instead of naming a winner.