Model comparison
GPT-5.5 Pro vs Llama 3.1-405B
GPT-5.5 Pro is the stronger model overall, scoring 64.3 to 30.4 on the Noometry Index.
Last verified . 5 shared benchmarks.
MetaSummary
- They share 5 benchmarks with published results for both. GPT-5.5 Pro scores higher in 3 categories and Llama 3.1-405B in 0 categories; 3 gaps are clear of the uncertainty.
- The widest gap is in math, where GPT-5.5 Pro leads 83.8 to 17.3.
- The biggest single-benchmark swing is OTIS Mock AIME 2024-2025: 100% for GPT-5.5 Pro and 9.7% for Llama 3.1-405B.
- Llama 3.1-405B has downloadable open weights; the other is API-only.
Side by side
| GPT-5.5 Pro | Llama 3.1-405B | |
|---|---|---|
| Provider | OpenAI | Meta |
| Noometry Index | 64.3 | 30.4 |
| Released | 2026-04-23 | 2024-07-23 |
| Weights | Proprietary | Open |
| Context window | 1.05M | — |
| Max output | 128K | — |
| Input $ / M tokens | $30 | — |
| Output $ / M tokens | $180 | — |
| Results tracked | 14 | 42 |
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Category by category
Coding Not comparable
GPT-5.5 Pro: —, Llama 3.1-405B: 32.7 (#257)
| Benchmark | GPT-5.5 Pro | Llama 3.1-405B |
|---|---|---|
| WeirdML | — | 21.4% |
| LMArena Coding | — | 1291 |
Agentic & Tool Use Not comparable
GPT-5.5 Pro: —, Llama 3.1-405B: 20.9 (#131)
| Benchmark | GPT-5.5 Pro | Llama 3.1-405B |
|---|---|---|
| TheAgentCompany | — | 7.4% |
| Cybench | — | 7.5% |
Reasoning GPT-5.5 Pro leads
GPT-5.5 Pro: 73.6 (#7), Llama 3.1-405B: 16.4 (#293)
| Benchmark | GPT-5.5 Pro | Llama 3.1-405B |
|---|---|---|
| SimpleBench | 76.9% | 23% |
| DTBench | 96% | 61.4% |
| Epoch Capabilities Index | 162.45 | 128.76 |
| ARC-AGI-2 | 84.6% | — |
| Kagi LLM Benchmark | — | 45% |
| ARC-AGI-1 | 96.5% | — |
| CritPt | 30.6% | — |
| Chess Puzzles | 64% | — |
| LMArena Hard Prompts | — | 1270 |
| LMCA | 53.9% | — |
| BIG-Bench Hard | — | 82.9% |
| ForecastBench | — | 59.9 |
| HellaSwag | — | 89.2% |
| PIQA | — | 85.9% |
| WinoGrande | — | 89.2% |
Math GPT-5.5 Pro leads
GPT-5.5 Pro: 83.8 (#8), Llama 3.1-405B: 17.3 (#283)
| Benchmark | GPT-5.5 Pro | Llama 3.1-405B |
|---|---|---|
| OTIS Mock AIME 2024-2025 | 100% | 9.7% |
| FrontierMath (Tiers 1-3) | 87.7% | — |
| FrontierMath Tier 4 | 78% | — |
| Omni-MATH | — | 24.9% |
| LMArena Math | — | 1281 |
| MATH Level 5 | — | 49.8% |
| FrontierMath (Feb 2025 set) | 52.4% | — |
| FrontierMath Tier 4 (v1) | 39.6% | — |
Knowledge GPT-5.5 Pro leads
GPT-5.5 Pro: 64.2 (#17), Llama 3.1-405B: 30.4 (#221)
| Benchmark | GPT-5.5 Pro | Llama 3.1-405B |
|---|---|---|
| GPQA Diamond | 93.9% | 50.9% |
| MMLU-Pro | — | 72.3% |
| Confabulations | — | 17.6% |
| GPQA (HELM) | — | 52.2% |
| LMArena Expert | — | 1243 |
| ARC (AI2) Challenge | — | 95.3% |
| MMLU | — | 84.5% |
| TriviaQA | — | 82.7% |
Multilingual Not comparable
GPT-5.5 Pro: —, Llama 3.1-405B: 40.9 (#209)
| Benchmark | GPT-5.5 Pro | Llama 3.1-405B |
|---|---|---|
| LMArena Non-English | — | 1248 |
| LMArena Chinese | — | 1242 |
| LMArena French | — | 1278 |
| LMArena German | — | 1252 |
| LMArena Japanese | — | 1208 |
| LMArena Korean | — | 1184 |
| LMArena Russian | — | 1265 |
| LMArena Spanish | — | 1259 |
Instruction Following Not comparable
GPT-5.5 Pro: —, Llama 3.1-405B: 66.1 (#209)
| Benchmark | GPT-5.5 Pro | Llama 3.1-405B |
|---|---|---|
| IFEval | — | 81.1% |
| LMArena Instruction Following | — | 1259 |
Long Context Not comparable
GPT-5.5 Pro: —, Llama 3.1-405B: 38.4 (#192)
| Benchmark | GPT-5.5 Pro | Llama 3.1-405B |
|---|---|---|
| LMArena Longer Query | — | 1266 |
Writing & Preference Not comparable
GPT-5.5 Pro: —, Llama 3.1-405B: 39.1 (#246)
| Benchmark | GPT-5.5 Pro | Llama 3.1-405B |
|---|---|---|
| LMArena Text | — | 1284 |
| LMArena Creative Writing | — | 1262 |
| EQ-Bench Creative Writing | — | 870 |
| WildBench | — | 78.3% |
| LMArena Multi-Turn | — | 1297 |
Frequently asked questions
Is GPT-5.5 Pro better than Llama 3.1-405B?
GPT-5.5 Pro is the stronger model overall, scoring 64.3 to 30.4 on the Noometry Index.
How many benchmarks do GPT-5.5 Pro and Llama 3.1-405B share?
5 benchmarks have published results for both models. GPT-5.5 Pro has 14 scored results on Noometry and Llama 3.1-405B has 42.