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GPT-4.1 Nano vs GPT-5.1-Codex

Updated October 21, 2026. 17 benchmarks have a result for both. Coding is ranked on the Vibe Coding Index; every other board is shown as published.

Replace GPT-4.1 Nano Replace GPT-5.1-Codex
GPT-4.1 NanoOpenAI
Coding
8.9
Overall
7.8
Output $/M
$0.40
0
GPT-5.1-CodexOpenAI
Coding
50.5
Overall
23.7
Output $/M
$10.00
17
vs boards won of 17 shared

Decision reading

Pick GPT-5.1-Codex for coding: it scores 50.5 on the Vibe Coding Index against 8.9 for GPT-4.1 Nano.

Pick GPT-4.1 Nano when output tokens cost 25.0x less, or when the context window is larger, 1.05M against 400K tokens.

Model AGPT-4.1 NanoOpenAI8.9/1001 independent benchmarkNo cost per solved taskModel BGPT-5.1-CodexOpenAI50.5/1002 independent benchmarks$0.892 per solved task
Shared results
17
GPT-4.1 Nano only
52
GPT-5.1-Codex only
9
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-4.1 Nano 8.9 from 1 benchmark, GPT-5.1-Codex 50.5 from 2 benchmarks.
Widest category
Math, 71.7 points apart on average over 2 shared benchmarks.
Widest single gap
AA Math Index: GPT-4.1 Nano 24.0 against GPT-5.1-Codex 95.7, 71.7 points apart on a 0 to 100 scale.
Output price
GPT-4.1 Nano $0.40 against GPT-5.1-Codex $10.00 per million output tokens, 25.0x apart.
Context window
GPT-4.1 Nano takes 1.05M tokens, GPT-5.1-Codex 400K.

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-4.1 NanoBarsGPT-5.1-CodexTies
Coding03
Intelligence01
Agentic work01
Reasoning02
Math02
Knowledge01
Web design05
General02
All shared boards017
CodingLike-for-likeFour of these boards feed the Vibe Coding Index03
Coding benchmarks for GPT-4.1 Nano and GPT-5.1-Codex
BenchmarkGPT-4.1 NanoGPT-5.1-CodexLeader
Aider polyglot8.9%Not measuredOnly GPT-4.1 Nano measured
SWE-bench VerifiedNot measured66.0%Only GPT-5.1-Codex measured
LMArena WebDevNot measured1337Only GPT-5.1-Codex measured
AA Coding Index11.1Not measuredOnly GPT-4.1 Nano measured
LiveCodeBench (Vals AI)42.7%85.5%GPT-5.1-Codex
Vibe Code Bench (Vals AI)Not measured13.1%Only GPT-5.1-Codex measured
LiveCodeBench (Artificial Analysis run)32.6%84.9%GPT-5.1-Codex
Terminal-Bench Hard (Artificial Analysis run)3.8%34.8%GPT-5.1-Codex
Terminal-BenchNot measured57.8%Only GPT-5.1-Codex measured
WeirdML19.0%Not measuredOnly GPT-4.1 Nano measured
ALE-BenchNot measured1244.9Only GPT-5.1-Codex measured
LMArena Text: coding1306Not measuredOnly GPT-4.1 Nano measured
LMArena Text: software and IT1305Not measuredOnly GPT-4.1 Nano measured
LMArena WebDev: HTMLNot measured1346Only GPT-5.1-Codex measured
Neither model has a result on the other 24 boards here
IntelligenceLike-for-likePublic boards, shown as published, kept out of the index01
Intelligence benchmarks for GPT-4.1 Nano and GPT-5.1-Codex
BenchmarkGPT-4.1 NanoGPT-5.1-CodexLeader
AA Intelligence Index7.823.7GPT-5.1-Codex
Epoch Capabilities Index129.5Not measuredOnly GPT-4.1 Nano measured
Agentic workLike-for-likePublic boards, shown as published, kept out of the index01
Agentic work benchmarks for GPT-4.1 Nano and GPT-5.1-Codex
BenchmarkGPT-4.1 NanoGPT-5.1-CodexLeader
Design Arena: agents building web appsNot measured1018Only GPT-5.1-Codex measured
Design Arena: agents building full-stack appsNot measured1086Only GPT-5.1-Codex measured
Design Arena: agents building mobile appsNot measured1191Only GPT-5.1-Codex measured
τ²-Bench Telecom17.3%83.0%GPT-5.1-Codex
Neither model has a result on the other 35 boards here
ReasoningLike-for-likePublic boards, shown as published, kept out of the index02
Reasoning benchmarks for GPT-4.1 Nano and GPT-5.1-Codex
BenchmarkGPT-4.1 NanoGPT-5.1-CodexLeader
GPQA Diamond50.8%Not measuredOnly GPT-4.1 Nano measured
MMMU Pro (Vals AI)55.0%Not measuredOnly GPT-4.1 Nano measured
GPQA Diamond (Artificial Analysis run)51.2%86.0%GPT-5.1-Codex
Humanity's Last Exam (Artificial Analysis run)3.8%25.7%GPT-5.1-Codex
GPQA Diamond (Epoch AI run)48.9%Not measuredOnly GPT-4.1 Nano measured
ARC-AGI0.0%Not measuredOnly GPT-4.1 Nano measured
ARC-AGI-20.0%Not measuredOnly GPT-4.1 Nano measured
Chess puzzles0.0%Not measuredOnly GPT-4.1 Nano measured
LMArena Text: hard prompts1286Not measuredOnly GPT-4.1 Nano measured
LMArena Text: expert1271Not measuredOnly GPT-4.1 Nano measured
LMArena Text: hard prompts in English1293Not measuredOnly GPT-4.1 Nano measured
Neither model has a result on the other 10 boards here
MathLike-for-likePublic boards, shown as published, kept out of the index02
Math benchmarks for GPT-4.1 Nano and GPT-5.1-Codex
BenchmarkGPT-4.1 NanoGPT-5.1-CodexLeader
AIME26.5%Not measuredOnly GPT-4.1 Nano measured
MATH 500 (Vals AI)80.2%Not measuredOnly GPT-4.1 Nano measured
MGSM (Vals AI)69.3%Not measuredOnly GPT-4.1 Nano measured
AA Math Index24.095.7GPT-5.1-Codex
AIME 2025 (Artificial Analysis run)24.0%95.7%GPT-5.1-Codex
OTIS Mock AIME28.9%Not measuredOnly GPT-4.1 Nano measured
MATH level 570.0%Not measuredOnly GPT-4.1 Nano measured
LMArena Text: math1274Not measuredOnly GPT-4.1 Nano measured
LMArena Text: mathematical work1274Not measuredOnly GPT-4.1 Nano measured
Neither model has a result on the other 4 boards here
KnowledgeLike-for-likePublic boards, shown as published, kept out of the index01
Knowledge benchmarks for GPT-4.1 Nano and GPT-5.1-Codex
BenchmarkGPT-4.1 NanoGPT-5.1-CodexLeader
MMLU Pro63.5%Not measuredOnly GPT-4.1 Nano measured
LegalBench (Vals AI)61.1%Not measuredOnly GPT-4.1 Nano measured
CorpFin (Vals AI)42.1%Not measuredOnly GPT-4.1 Nano measured
TaxEval (Vals AI)60.8%Not measuredOnly GPT-4.1 Nano measured
MortgageTax (Vals AI)52.8%Not measuredOnly GPT-4.1 Nano measured
MedQA (Vals AI)68.2%Not measuredOnly GPT-4.1 Nano measured
MMLU Pro (Artificial Analysis run)65.7%86.0%GPT-5.1-Codex
SimpleQA Verified6.0%Not measuredOnly GPT-4.1 Nano measured
LMArena Text: science1297Not measuredOnly GPT-4.1 Nano measured
LMArena Text: medicine and healthcare1276Not measuredOnly GPT-4.1 Nano measured
LMArena Text: legal and government1300Not measuredOnly GPT-4.1 Nano measured
LMArena Text: business and finance1267Not measuredOnly GPT-4.1 Nano measured
Neither model has a result on the other 5 boards here
Web designLike-for-likePublic boards, shown as published, kept out of the index05
Web design benchmarks for GPT-4.1 Nano and GPT-5.1-Codex
BenchmarkGPT-4.1 NanoGPT-5.1-CodexLeader
Design Arena: websites9731162GPT-5.1-Codex
Design Arena: UI components9161237GPT-5.1-Codex
Design Arena: game dev9711138GPT-5.1-Codex
Design Arena: data viz8911213GPT-5.1-Codex
Design Arena: 3D925Not measuredOnly GPT-4.1 Nano measured
Design Arena: all code categories9631153GPT-5.1-Codex
Neither model has a result on the other 3 boards here
GeneralLike-for-likePublic boards, shown as published, kept out of the index02
General benchmarks for GPT-4.1 Nano and GPT-5.1-Codex
BenchmarkGPT-4.1 NanoGPT-5.1-CodexLeader
IFBench32.0%70.0%GPT-5.1-Codex
Long context reasoning (AA-LCR)20.3%69.3%GPT-5.1-Codex
DTBench52.5%Not measuredOnly GPT-4.1 Nano measured
LMCA5.5%Not measuredOnly GPT-4.1 Nano measured
Fiction.LiveBench25.0%Not measuredOnly GPT-4.1 Nano measured
LMArena Text1285Not measuredOnly GPT-4.1 Nano measured
LMArena Text: instruction following1266Not measuredOnly GPT-4.1 Nano measured
LMArena Text: creative writing1260Not measuredOnly GPT-4.1 Nano measured
LMArena Vision1063Not measuredOnly GPT-4.1 Nano measured
LMArena Text: English1303Not measuredOnly GPT-4.1 Nano measured
LMArena Text: non-English1260Not measuredOnly GPT-4.1 Nano measured
LMArena Text: Chinese1270Not measuredOnly GPT-4.1 Nano measured
LMArena Text: German1288Not measuredOnly GPT-4.1 Nano measured
LMArena Text: Japanese1198Not measuredOnly GPT-4.1 Nano measured
LMArena Text: Russian1261Not measuredOnly GPT-4.1 Nano measured
LMArena Text: multi-turn1277Not measuredOnly GPT-4.1 Nano measured
LMArena Text: longer queries1283Not measuredOnly GPT-4.1 Nano measured
LMArena Text: writing and language1261Not measuredOnly GPT-4.1 Nano measured
LMArena Text: entertainment and media1243Not measuredOnly GPT-4.1 Nano measured
LMArena Vision: English1101Not measuredOnly GPT-4.1 Nano measured
Neither model has a result on the other 26 boards here
Image generationNot comparablePublic boards, shown as published, kept out of the index0 boards, none shared
Image generation benchmarks for GPT-4.1 Nano and GPT-5.1-Codex
BenchmarkGPT-4.1 NanoGPT-5.1-CodexLeader
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-4.1 Nano$0.0003Fits in one request
GPT-5.1-Codex$0.0063Fits in one request

GPT-4.1 Nano costs less

Repository review

50K input + 3K output tokens

GPT-4.1 Nano$0.0062Fits in one request
GPT-5.1-Codex$0.092Fits in one request

GPT-4.1 Nano costs less

Agent loop

200K input + 10K output tokens

GPT-4.1 Nano$0.024Fits in one request
GPT-5.1-Codex$0.350Fits in one request

GPT-4.1 Nano 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-4.1 Nano and GPT-5.1-Codex
SpecificationOpenAI GPT-4.1 NanoOpenAI GPT-5.1-Codex
MakerOpenAIOpenAI
WeightsNo public weights listedNo public weights listed
ReleasedApril 14, 2025November 13, 2025
Context window1.05M400K
Input $/Mtok$0.10$1.25
Output $/Mtok$0.40$10.00
Coding index8.950.5
Independent measurements behind it12
Cost per solved taskNot computable$0.892
SourceOpenRouter listingOpenRouter listing

Questions

Is GPT-4.1 Nano better than GPT-5.1-Codex for coding?

Pick GPT-5.1-Codex for coding: it scores 50.5 on the Vibe Coding Index against 8.9 for GPT-4.1 Nano. Pick GPT-4.1 Nano when output tokens cost 25.0x less, or when the context window is larger, 1.05M against 400K tokens.

Which is cheaper, GPT-4.1 Nano or GPT-5.1-Codex?

GPT-4.1 Nano costs $0.10 per million input tokens and $0.40 per million output tokens; GPT-5.1-Codex costs $1.25 and $10.00. Cost per solved task is known for GPT-5.1-Codex only.

Which has the bigger context window, GPT-4.1 Nano or GPT-5.1-Codex?

GPT-4.1 Nano, with 1.05M tokens against 400K.

How many benchmarks is the GPT-4.1 Nano vs GPT-5.1-Codex comparison based on?

17 benchmarks have a result for both models as of October 21, 2026. GPT-4.1 Nano's coding index rests on 1 independent benchmark and GPT-5.1-Codex's on 2. Where only one model has a result, the page says so instead of naming a winner.

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