Model comparison
GPT-5.1 vs GPT-5.5 Pro
GPT-5.5 Pro is the stronger model overall, scoring 64.3 to 49.0 on the Noometry Index. GPT-5.1 costs 20× less per token, which makes it the better buy when GPT-5.5 Pro's lead doesn't matter for your workload.
Last verified . 12 shared benchmarks.
Summary
- They share 12 benchmarks with published results for both. GPT-5.1 scores higher in 0 categories and GPT-5.5 Pro in 3 categories; 3 gaps are clear of the uncertainty.
- The widest gap is in reasoning, where GPT-5.5 Pro leads 73.3 to 39.8.
- The biggest single-benchmark swing is ARC-AGI-2: 17.6% for GPT-5.1 and 84.6% for GPT-5.5 Pro.
- GPT-5.1 is cheaper at $1.25 / $10 per million input/output tokens, against $30 / $180 for GPT-5.5 Pro.
- GPT-5.5 Pro accepts more context: 1.05M tokens versus 400K.
Side by side
| GPT-5.1 | GPT-5.5 Pro | |
|---|---|---|
| Provider | OpenAI | OpenAI |
| Noometry Index | 49.0 | 64.3 |
| Released | 2025-11-13 | 2026-04-23 |
| Weights | Proprietary | Proprietary |
| Context window | 400K | 1.05M |
| Max output | 128K | 128K |
| Input $ / M tokens | $1.25 | $30 |
| Output $ / M tokens | $10 | $180 |
| Results tracked | 63 | 14 |
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Category by category
Coding Not comparable
GPT-5.1: 46.4 (#66), GPT-5.5 Pro: —
| Benchmark | GPT-5.1 | GPT-5.5 Pro |
|---|---|---|
| SWE-bench Verified | 68% | — |
| SWE-bench Verified (bash only) | 66% | — |
| LMArena WebDev | 1395 | — |
| SciCode | 43.3% | — |
| GSO | 13.7% | — |
| WeirdML | 60.8% | — |
| LiveBench Coding | 72.5% | — |
| LMArena Coding | 1454 | — |
| ALE-Bench | 1,192 | — |
Agentic & Tool Use Not comparable
GPT-5.1: 32.7 (#60), GPT-5.5 Pro: —
| Benchmark | GPT-5.1 | GPT-5.5 Pro |
|---|---|---|
| Terminal-Bench | 47.6% | — |
| DeepResearch Bench | 42.8% | — |
| LMArena Search | 1199 | — |
| Vending-Bench 2 | 1,473 | — |
Reasoning GPT-5.5 Pro leads
GPT-5.1: 39.8 (#58), GPT-5.5 Pro: 73.3 (#10)
| Benchmark | GPT-5.1 | GPT-5.5 Pro |
|---|---|---|
| ARC-AGI-2 | 17.6% | 84.6% |
| SimpleBench | 53.2% | 76.9% |
| ARC-AGI-1 | 72.8% | 96.5% |
| CritPt | 4.9% | 30.6% |
| Chess Puzzles | 32% | 64% |
| DTBench | 90.1% | 96% |
| LMCA | 43.9% | 53.9% |
| Epoch Capabilities Index | 149.64 | 162.07 |
| EnigmaEval | 11.2% | — |
| LiveBench Reasoning | 95.8% | — |
| LMArena Hard Prompts | 1457 | — |
| Mystery Game Puzzles | 19% | — |
| LiveBench Data Analysis | 72.1% | — |
| ForecastBench | 58.1 | — |
| LiveBench | 78.8% | — |
Math GPT-5.5 Pro leads
GPT-5.1: 52.2 (#51), GPT-5.5 Pro: 84.0 (#10)
| Benchmark | GPT-5.1 | GPT-5.5 Pro |
|---|---|---|
| OTIS Mock AIME 2024-2025 | 88.6% | 100% |
| FrontierMath (Feb 2025 set) | 31% | 52.4% |
| FrontierMath Tier 4 (v1) | 12.5% | 39.6% |
| FrontierMath (Tiers 1-3) | — | 87.7% |
| FrontierMath Tier 4 | — | 78% |
| Omni-MATH | 46.4% | — |
| LiveBench Math | 94.5% | — |
| LMArena Math | 1447 | — |
Knowledge GPT-5.5 Pro leads
GPT-5.1: 50.6 (#71), GPT-5.5 Pro: 64.1 (#19)
| Benchmark | GPT-5.1 | GPT-5.5 Pro |
|---|---|---|
| GPQA Diamond | 87.6% | 93.9% |
| 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-5.5 Pro: —
| Benchmark | GPT-5.1 | GPT-5.5 Pro |
|---|---|---|
| LMArena Vision | 1250 | — |
| VPCT | 58.7% | — |
| LMArena Document | 1403 | — |
Multilingual Not comparable
GPT-5.1: 53.8 (#56), GPT-5.5 Pro: —
| Benchmark | GPT-5.1 | GPT-5.5 Pro |
|---|---|---|
| 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-5.5 Pro: —
| Benchmark | GPT-5.1 | GPT-5.5 Pro |
|---|---|---|
| LiveBench Instruction Following | 93.3% | — |
| IFEval | 93.5% | — |
| LMArena Instruction Following | 1443 | — |
Long Context Not comparable
GPT-5.1: 47.6 (#14), GPT-5.5 Pro: —
| Benchmark | GPT-5.1 | GPT-5.5 Pro |
|---|---|---|
| CL-bench | 23.7% | — |
| CL-bench Life | 17.3% | — |
| LMArena Longer Query | 1447 | — |
Writing & Preference Not comparable
GPT-5.1: 64.5 (#55), GPT-5.5 Pro: —
| Benchmark | GPT-5.1 | GPT-5.5 Pro |
|---|---|---|
| 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-5.5 Pro?
GPT-5.5 Pro is the stronger model overall, scoring 64.3 to 49.0 on the Noometry Index. GPT-5.1 costs 20× less per token, which makes it the better buy when GPT-5.5 Pro's lead doesn't matter for your workload.
Which is cheaper, GPT-5.1 or GPT-5.5 Pro?
GPT-5.1 is cheaper. It lists at $1.25 per million input tokens and $10 per million output tokens; GPT-5.5 Pro lists at $30 and $180.
Which has the bigger context window?
GPT-5.5 Pro does, with 1.05M tokens against 400K.
How many benchmarks do GPT-5.1 and GPT-5.5 Pro share?
12 benchmarks have published results for both models. GPT-5.1 has 63 scored results on Noometry and GPT-5.5 Pro has 14.