Model comparison
GPT-5.1 vs GPT-5-Codex
GPT-5.1 is the stronger model overall, scoring 49.0 to 37.9 on the Noometry Index.
Last verified . 2 shared benchmarks.
Summary
- They share 2 benchmarks with published results for both. GPT-5.1 scores higher in 3 categories and GPT-5-Codex in 0 categories; 3 gaps are clear of the uncertainty.
- The widest gap is in reasoning, where GPT-5.1 leads 39.8 to 30.9.
- The biggest single-benchmark swing is WeirdML: 60.8% for GPT-5.1 and 54.5% for GPT-5-Codex.
- Both cost about the same: $1.25 input and $10 output per million tokens.
Side by side
| GPT-5.1 | GPT-5-Codex | |
|---|---|---|
| Provider | OpenAI | OpenAI |
| Noometry Index | 49.0 | 37.9 |
| Released | 2025-11-13 | 2025-09-15 |
| Weights | Proprietary | Proprietary |
| Context window | 400K | 400K |
| Max output | 128K | 128K |
| Input $ / M tokens | $1.25 | $1.25 |
| Output $ / M tokens | $10 | $10 |
| Results tracked | 63 | 3 |
Sponsored placements are available on pages like this one. Advertise on Noometry
Category by category
Coding GPT-5.1 leads
GPT-5.1: 46.4 (#66), GPT-5-Codex: 42.4 (#103)
| Benchmark | GPT-5.1 | GPT-5-Codex |
|---|---|---|
| WeirdML | 60.8% | 54.5% |
| SWE-bench Verified | 68% | — |
| SWE-bench Verified (bash only) | 66% | — |
| LMArena WebDev | 1395 | — |
| SciCode | 43.3% | — |
| GSO | 13.7% | — |
| LiveBench Coding | 72.5% | — |
| LMArena Coding | 1454 | — |
| ALE-Bench | 1,192 | — |
Agentic & Tool Use GPT-5.1 leads
GPT-5.1: 32.7 (#60), GPT-5-Codex: 31.0 (#72)
| Benchmark | GPT-5.1 | GPT-5-Codex |
|---|---|---|
| Terminal-Bench | 47.6% | 44.3% |
| DeepResearch Bench | 42.8% | — |
| LMArena Search | 1199 | — |
| Vending-Bench 2 | 1,473 | — |
Reasoning GPT-5.1 leads
GPT-5.1: 39.8 (#58), GPT-5-Codex: 30.9 (#83)
| Benchmark | GPT-5.1 | GPT-5-Codex |
|---|---|---|
| ARC-AGI-2 | 17.6% | — |
| SimpleBench | 53.2% | — |
| Kagi LLM Benchmark | — | 70.3% |
| ARC-AGI-1 | 72.8% | — |
| CritPt | 4.9% | — |
| Chess Puzzles | 32% | — |
| EnigmaEval | 11.2% | — |
| LiveBench Reasoning | 95.8% | — |
| LMArena Hard Prompts | 1457 | — |
| Mystery Game Puzzles | 19% | — |
| DTBench | 90.1% | — |
| LiveBench Data Analysis | 72.1% | — |
| LMCA | 43.9% | — |
| Epoch Capabilities Index | 149.64 | — |
| ForecastBench | 58.1 | — |
| LiveBench | 78.8% | — |
Math Not comparable
GPT-5.1: 52.2 (#51), GPT-5-Codex: —
| Benchmark | GPT-5.1 | GPT-5-Codex |
|---|---|---|
| OTIS Mock AIME 2024-2025 | 88.6% | — |
| Omni-MATH | 46.4% | — |
| LiveBench Math | 94.5% | — |
| LMArena Math | 1447 | — |
| FrontierMath (Feb 2025 set) | 31% | — |
| FrontierMath Tier 4 (v1) | 12.5% | — |
Knowledge Not comparable
GPT-5.1: 50.6 (#71), GPT-5-Codex: —
| Benchmark | GPT-5.1 | GPT-5-Codex |
|---|---|---|
| GPQA Diamond | 87.6% | — |
| Humanity's Last Exam | 23.7% | — |
| SimpleQA Verified | 48% | — |
| MMLU-Pro | 57.9% | — |
| Vectara Hallucination Rate | 10.9% | — |
| GPQA (HELM) | 44.2% | — |
| LMArena Expert | 1470 | — |
Multimodal Not comparable
GPT-5.1: 44.8 (#19), GPT-5-Codex: —
| Benchmark | GPT-5.1 | GPT-5-Codex |
|---|---|---|
| LMArena Vision | 1250 | — |
| VPCT | 58.7% | — |
| LMArena Document | 1403 | — |
Multilingual Not comparable
GPT-5.1: 53.8 (#56), GPT-5-Codex: —
| Benchmark | GPT-5.1 | GPT-5-Codex |
|---|---|---|
| LMArena Non-English | 1431 | — |
| LMArena Chinese | 1495 | — |
| LMArena French | 1450 | — |
| LMArena German | 1438 | — |
| LMArena Japanese | 1453 | — |
| LMArena Korean | 1401 | — |
| LMArena Russian | 1435 | — |
| LMArena Spanish | 1433 | — |
Instruction Following Not comparable
GPT-5.1: 83.9 (#1), GPT-5-Codex: —
| Benchmark | GPT-5.1 | GPT-5-Codex |
|---|---|---|
| LiveBench Instruction Following | 93.3% | — |
| IFEval | 93.5% | — |
| LMArena Instruction Following | 1443 | — |
Long Context Not comparable
GPT-5.1: 47.6 (#14), GPT-5-Codex: —
| Benchmark | GPT-5.1 | GPT-5-Codex |
|---|---|---|
| CL-bench | 23.7% | — |
| CL-bench Life | 17.3% | — |
| LMArena Longer Query | 1447 | — |
Writing & Preference Not comparable
GPT-5.1: 64.5 (#55), GPT-5-Codex: —
| Benchmark | GPT-5.1 | GPT-5-Codex |
|---|---|---|
| LMArena Text | 1443 | — |
| LMArena Creative Writing | 1427 | — |
| WildBench | 86.3% | — |
| LMArena Multi-Turn | 1450 | — |
| LiveBench Language | 80.2% | — |
Frequently asked questions
Is GPT-5.1 better than GPT-5-Codex?
GPT-5.1 is the stronger model overall, scoring 49.0 to 37.9 on the Noometry Index.
Which is cheaper, GPT-5.1 or GPT-5-Codex?
GPT-5-Codex is cheaper. It lists at $1.25 per million input tokens and $10 per million output tokens; GPT-5.1 lists at $1.25 and $10.
Is GPT-5.1 or GPT-5-Codex better for coding?
GPT-5.1 scores higher on coding benchmarks: 46.4 versus 42.4 in the Noometry coding category.
Which has the bigger context window?
Both accept 400K tokens.
How many benchmarks do GPT-5.1 and GPT-5-Codex share?
2 benchmarks have published results for both models. GPT-5.1 has 63 scored results on Noometry and GPT-5-Codex has 3.