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GPT-5 vs gpt-oss-20b

Updated October 21, 2026. 59 benchmarks have a result for both. Coding is ranked on the Vibe Coding Index; every other board is shown as published.

Replace GPT-5 Replace gpt-oss-20b
GPT-5OpenAI
Coding
38.8
Overall
23.0
Output $/M
$10.00
59
gpt-oss-20bOpenAI
Coding
No data
Overall
10.0
Output $/M
$0.15
0
vs boards won of 59 shared

Decision reading

Only GPT-5 has a coding score, 38.8 on the Vibe Coding Index; gpt-oss-20b has none, so the two cannot be ranked on coding.

gpt-oss-20b has the edge where output tokens cost 66.7x less.

Model AGPT-5OpenAI38.8/1003 independent benchmarks$0.39 per solved taskModel Bgpt-oss-20bOpenAINot benchmarkedNo coding benchmarkNo cost per solved task
Shared results
59
GPT-5 only
50
gpt-oss-20b only
1
Like-for-like categories
8 of 9

Shared results can support a head-to-head reading. Results only one model has describe coverage, not superiority.

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.

At a glance

Coding index
GPT-5 38.8 from 3 benchmarks, gpt-oss-20b not benchmarked.
Widest category
Web design, 38.8 points apart on average over 2 shared benchmarks.
Widest single gap
Terminal-Bench: GPT-5 49.6% against gpt-oss-20b 3.4%, 46.2 points apart on a 0 to 100 scale.
Output price
GPT-5 $10.00 against gpt-oss-20b $0.15 per million output tokens, 66.7x apart.
Context window
GPT-5 takes 400K 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.

Boards won, where both have a result
CategoryGPT-5Barsgpt-oss-20bTies
Coding80
Intelligence20
Agentic work10
Reasoning70
Math80
Knowledge110
Web design20
General200
All shared boards590
CodingLike-for-likeSix of these boards feed the Vibe Coding Index80
Coding benchmarks for GPT-5 and gpt-oss-20b
BenchmarkGPT-5gpt-oss-20bLeader
Aider polyglot88.0%Not measuredOnly GPT-5 measured
SWE-bench Verified74.4%Not measuredOnly GPT-5 measured
LMArena WebDev1418Not measuredOnly GPT-5 measured
AA Coding Index37.8Not measuredOnly GPT-5 measured
LiveCodeBench (Vals AI)85.9%80.4%GPT-5
SWE-bench Verified (Vals AI)69.0%Not measuredOnly GPT-5 measured
Vibe Code Bench (Vals AI)20.1%Not measuredOnly GPT-5 measured
LiveCodeBench (Artificial Analysis run)84.6%77.7%GPT-5
SciCodeNot measured38.9%Only gpt-oss-20b measured
Terminal-Bench Hard (Artificial Analysis run)37.9%10.6%GPT-5
Terminal-Bench49.6%3.4%GPT-5
GSO-Bench6.9%Not measuredOnly GPT-5 measured
WeirdML60.7%40.9%GPT-5
ALE-Bench807.6566.0GPT-5
LMArena Text: coding14361307GPT-5
LMArena Text: software and IT14201311GPT-5
LMArena WebDev: HTML1427Not measuredOnly GPT-5 measured
Neither model has a result on the other 21 boards here
IntelligenceLike-for-likePublic boards, shown as published, kept out of the index20
Intelligence benchmarks for GPT-5 and gpt-oss-20b
BenchmarkGPT-5gpt-oss-20bLeader
AA Intelligence Index23.010.0GPT-5
Epoch Capabilities Index150.0137.7GPT-5
Agentic workLike-for-likePublic boards, shown as published, kept out of the index10
Agentic work benchmarks for GPT-5 and gpt-oss-20b
BenchmarkGPT-5gpt-oss-20bLeader
τ²-Bench Telecom86.5%60.2%GPT-5
METR time horizons69.6%Not measuredOnly GPT-5 measured
Remote Labor Index1.7%Not measuredOnly GPT-5 measured
GDPval34.8%Not measuredOnly GPT-5 measured
BALROG32.8%Not measuredOnly GPT-5 measured
DeepResearch Bench49.6%Not measuredOnly GPT-5 measured
Neither model has a result on the other 33 boards here
ReasoningLike-for-likePublic boards, shown as published, kept out of the index70
Reasoning benchmarks for GPT-5 and gpt-oss-20b
BenchmarkGPT-5gpt-oss-20bLeader
GPQA Diamond85.6%68.9%GPT-5
MMMU Pro (Vals AI)81.5%Not measuredOnly GPT-5 measured
GPQA Diamond (Artificial Analysis run)85.4%68.8%GPT-5
Humanity's Last Exam (Artificial Analysis run)28.5%11.0%GPT-5
GPQA Diamond (Epoch AI run)86.2%60.8%GPT-5
ARC-AGI65.7%Not measuredOnly GPT-5 measured
ARC-AGI-29.9%Not measuredOnly GPT-5 measured
SimpleBench56.7%Not measuredOnly GPT-5 measured
Chess puzzles36.0%Not measuredOnly GPT-5 measured
Mystery game puzzles23.0%Not measuredOnly GPT-5 measured
EBR-bench12.7%Not measuredOnly GPT-5 measured
VPCT66.0%Not measuredOnly GPT-5 measured
LMArena Text: hard prompts14151274GPT-5
LMArena Text: expert14191258GPT-5
LMArena Text: hard prompts in English14191292GPT-5
LMArena Vision: diagrams1252Not measuredOnly GPT-5 measured
LMArena Vision: homework1278Not measuredOnly GPT-5 measured
Neither model has a result on the other 4 boards here
MathLike-for-likePublic boards, shown as published, kept out of the index80
Math benchmarks for GPT-5 and gpt-oss-20b
BenchmarkGPT-5gpt-oss-20bLeader
AIME93.4%86.0%GPT-5
MATH 500 (Vals AI)96.0%94.2%GPT-5
MGSM (Vals AI)92.8%89.0%GPT-5
AA Math Index94.389.3GPT-5
AIME 2025 (Artificial Analysis run)94.3%89.3%GPT-5
OTIS Mock AIME91.4%65.3%GPT-5
FrontierMath, tiers 1 to 355.4%Not measuredOnly GPT-5 measured
FrontierMath, tier 422.0%Not measuredOnly GPT-5 measured
ProofBench18.0%Not measuredOnly GPT-5 measured
MATH level 598.1%Not measuredOnly GPT-5 measured
LMArena Text: math14071317GPT-5
LMArena Text: mathematical work14051305GPT-5
Neither model has a result on the other 1 board here
KnowledgeLike-for-likePublic boards, shown as published, kept out of the index110
Knowledge benchmarks for GPT-5 and gpt-oss-20b
BenchmarkGPT-5gpt-oss-20bLeader
MMLU Pro86.5%71.6%GPT-5
LegalBench (Vals AI)86.0%70.8%GPT-5
CaseLaw (Vals AI)66.5%43.8%GPT-5
CorpFin (Vals AI)61.1%53.1%GPT-5
TaxEval (Vals AI)73.4%63.7%GPT-5
MortgageTax (Vals AI)65.5%Not measuredOnly GPT-5 measured
MedQA (Vals AI)96.3%82.9%GPT-5
MedCode (Vals AI)49.6%Not measuredOnly GPT-5 measured
MMLU Pro (Artificial Analysis run)87.1%74.8%GPT-5
SimpleQA Verified50.1%Not measuredOnly GPT-5 measured
GeoBench81.0%Not measuredOnly GPT-5 measured
LMArena Text: science14161296GPT-5
LMArena Text: medicine and healthcare14131310GPT-5
LMArena Text: legal and government14311280GPT-5
LMArena Text: business and finance14001284GPT-5
Neither model has a result on the other 2 boards here
Web designLike-for-likePublic boards, shown as published, kept out of the index20
Web design benchmarks for GPT-5 and gpt-oss-20b
BenchmarkGPT-5gpt-oss-20bLeader
Design Arena: websites1185853GPT-5
Design Arena: UI components1180Not measuredOnly GPT-5 measured
Design Arena: game dev1185Not measuredOnly GPT-5 measured
Design Arena: data viz1221933GPT-5
Design Arena: 3D1056Not measuredOnly GPT-5 measured
Design Arena: all code categories1168Not measuredOnly GPT-5 measured
Design Arena: SVG1189Not measuredOnly GPT-5 measured
Design Arena: ASCII art1140Not measuredOnly GPT-5 measured
Neither model has a result on the other 1 board here
GeneralLike-for-likePublic boards, shown as published, kept out of the index200
General benchmarks for GPT-5 and gpt-oss-20b
BenchmarkGPT-5gpt-oss-20bLeader
SAGE (Vals AI)43.7%Not measuredOnly GPT-5 measured
MedScribe (Vals AI)83.7%Not measuredOnly GPT-5 measured
IFBench73.1%65.1%GPT-5
Long context reasoning (AA-LCR)78.2%34.7%GPT-5
DTBench90.7%68.0%GPT-5
LMCA40.0%14.5%GPT-5
Fiction.LiveBench97.2%Not measuredOnly GPT-5 measured
Creative writing (Lech Mazur)86.0%Not measuredOnly GPT-5 measured
LMArena Text14061288GPT-5
LMArena Text: instruction following13881236GPT-5
LMArena Text: creative writing13651201GPT-5
LMArena Vision1232Not measuredOnly GPT-5 measured
LMArena Text: English14091303GPT-5
LMArena Text: non-English13971269GPT-5
LMArena Text: Chinese14221315GPT-5
LMArena Text: German14161255GPT-5
LMArena Text: Japanese14091244GPT-5
LMArena Text: Korean13601236GPT-5
LMArena Text: French1409Not measuredOnly GPT-5 measured
LMArena Text: Spanish13991267GPT-5
LMArena Text: Russian14071278GPT-5
LMArena Text: Polish14311252GPT-5
LMArena Text: multi-turn14261268GPT-5
LMArena Text: longer queries13991250GPT-5
LMArena Text: writing and language13841238GPT-5
LMArena Text: entertainment and media13791216GPT-5
LMArena Vision: English1231Not measuredOnly GPT-5 measured
LMArena Vision: Chinese1267Not measuredOnly GPT-5 measured
LMArena Vision: reading text1246Not measuredOnly GPT-5 measured
LMArena Vision: humor1219Not measuredOnly GPT-5 measured
LMArena Vision: captioning1212Not measuredOnly GPT-5 measured
LMArena Vision: recognizing things1263Not measuredOnly GPT-5 measured
LMArena Vision: creative writing1210Not measuredOnly GPT-5 measured
Neither model has a result on the other 13 boards here
Image generationNot comparablePublic boards, shown as published, kept out of the index0 boards, none shared
Image generation benchmarks for GPT-5 and gpt-oss-20b
BenchmarkGPT-5gpt-oss-20bLeader
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

GPT-5$0.0063Fits in one request
gpt-oss-20b$0.0001Fits in one request

gpt-oss-20b costs less

Repository review

50K input + 3K output tokens

GPT-5$0.092Fits in one request
gpt-oss-20b$0.0019Fits in one request

gpt-oss-20b costs less

Agent loop

200K input + 10K output tokens

GPT-5$0.350Fits 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.

Specifications of GPT-5 and gpt-oss-20b
SpecificationOpenAI GPT-5OpenAI gpt-oss-20b
MakerOpenAIOpenAI
WeightsNo public weights listedOpen weights
ReleasedAugust 7, 2025August 5, 2025
Context window400K131K
Input $/Mtok$1.25$0.03
Output $/Mtok$10.00$0.15
Coding index38.8Not benchmarked
Independent measurements behind it30
Cost per solved task$0.39Not computable
SourceOpenRouter listingOpenRouter listing

Questions

Is GPT-5 better than gpt-oss-20b for coding?

Only GPT-5 has a coding score, 38.8 on the Vibe Coding Index; gpt-oss-20b has none, so the two cannot be ranked on coding. gpt-oss-20b has the edge where output tokens cost 66.7x less.

Which is cheaper, GPT-5 or gpt-oss-20b?

GPT-5 costs $1.25 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 GPT-5 only.

Which has the bigger context window, GPT-5 or gpt-oss-20b?

GPT-5, with 400K tokens against 131K.

How many benchmarks is the GPT-5 vs gpt-oss-20b comparison based on?

59 benchmarks have a result for both models as of October 21, 2026. GPT-5's coding index rests on 3 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.

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