Model comparison
GLM-5.1 vs GPT-5.5
GPT-5.5 is the stronger model overall, scoring 63.4 to 47.8 on the Noometry Index. GLM-5.1 costs 5.2× less per token, which makes it the better buy when GPT-5.5's lead doesn't matter for your workload.
Last verified . 40 shared benchmarks.
Summary
- They share 40 benchmarks with published results for both. GLM-5.1 scores higher in 0 categories and GPT-5.5 in 9 categories; 9 gaps are clear of the uncertainty.
- The widest gap is in reasoning, where GPT-5.5 leads 72.8 to 39.1.
- The biggest single-benchmark swing is GBAEval: 0% for GLM-5.1 and 53.2% for GPT-5.5.
- GLM-5.1 is cheaper at $1.40 / $4.40 per million input/output tokens, against $5 / $30 for GPT-5.5.
- GPT-5.5 accepts more context: 1.05M tokens versus 200K.
- GLM-5.1 has downloadable open weights; the other is API-only.
Side by side
| GLM-5.1 | GPT-5.5 | |
|---|---|---|
| Provider | Z.ai (Zhipu) | OpenAI |
| Noometry Index | 47.8 | 63.4 |
| Released | 2026-04-07 | 2026-04-23 |
| Weights | Open | Proprietary |
| Context window | 200K | 1.05M |
| Max output | 131K | 128K |
| Input $ / M tokens | $1.40 | $5 |
| Output $ / M tokens | $4.40 | $30 |
| Results tracked | 41 | 71 |
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Category by category
Coding GPT-5.5 leads
GLM-5.1: 48.7 (#55), GPT-5.5: 58.2 (#17)
| Benchmark | GLM-5.1 | GPT-5.5 |
|---|---|---|
| SWE-bench Verified | 74.2% | 80.6% |
| LMArena WebDev | 1508 | 1513 |
| SciCode | 43.8% | 56.1% |
| WeirdML | 57.1% | 84.9% |
| LMArena Coding | 1485 | 1494 |
| ALE-Bench | 887.1 | 1,943 |
| DeepSWE | — | 67% |
| FrontierCode | — | 43% |
| GSO | — | 40.2% |
| MirrorCode | — | 10% |
Agentic & Tool Use GPT-5.5 leads
GLM-5.1: 24.9 (#113), GPT-5.5: 50.7 (#6)
| Benchmark | GLM-5.1 | GPT-5.5 |
|---|---|---|
| APEX-Agents | 40.9% | 55.1% |
| ExploitBench | 18.1% | 47.4% |
| GBAEval | 0% | 53.2% |
| Vending-Bench 2 | 5,634 | 7,524 |
| Terminal-Bench | — | 84.7% |
| OSWorld 2.0 | — | 13% |
| Remote Labor Index | — | 6.3% |
| τ²-bench Banking | — | 44.6% |
| DeepResearch Bench | — | 54% |
| PostTrainBench | — | 27.2% |
| GDP.pdf | — | 26% |
| LMArena Search | — | 1242 |
Reasoning GPT-5.5 leads
GLM-5.1: 39.1 (#60), GPT-5.5: 72.8 (#11)
| Benchmark | GLM-5.1 | GPT-5.5 |
|---|---|---|
| SimpleBench | 55.1% | 69% |
| NYT Connections (extended) | 77.7% | 96.2% |
| CritPt | 4.6% | 27.1% |
| Chess Puzzles | 19% | 54% |
| LMArena Hard Prompts | 1472 | 1489 |
| Epoch Capabilities Index | 149.84 | 159.1 |
| ARC-AGI-2 | — | 85% |
| Kagi LLM Benchmark | — | 88.8% |
| ARC-AGI-1 | — | 95% |
| Thematic Generalization | 69.8% | — |
| EBR-Bench | — | 34.3% |
| Mystery Game Puzzles | — | 56% |
| DTBench | — | 96% |
| LMCA | — | 54.3% |
| Surface Evolver Bench | — | 88.1% |
| Bench to the Future 3 | — | 0.14 |
| ForecastBench | — | 60.6 |
Math GPT-5.5 leads
GLM-5.1: 49.7 (#60), GPT-5.5: 81.7 (#11)
| Benchmark | GLM-5.1 | GPT-5.5 |
|---|---|---|
| FrontierMath (Tiers 1-3) | 36.8% | 85.3% |
| MathArena Final-Answer Competitions | 67.1% | 94.3% |
| OTIS Mock AIME 2024-2025 | 93.3% | 100% |
| ProofBench | 22.2% | 50% |
| LMArena Math | 1473 | 1486 |
| FrontierMath (Feb 2025 set) | 33.4% | 51.7% |
| FrontierMath Tier 4 (v1) | 12.5% | 35.4% |
| FrontierMath Tier 4 | — | 72.5% |
| FrontierMath Erdős | — | 0% |
Knowledge GPT-5.5 leads
GLM-5.1: 54.9 (#50), GPT-5.5: 64.4 (#17)
| Benchmark | GLM-5.1 | GPT-5.5 |
|---|---|---|
| GPQA Diamond | 89.9% | 94% |
| SimpleQA Verified | 34% | 63% |
| LMArena Expert | 1476 | 1508 |
| Vectara Hallucination Rate | — | 9.3% |
Multimodal Not comparable
GLM-5.1: —, GPT-5.5: 46.9 (#12)
| Benchmark | GLM-5.1 | GPT-5.5 |
|---|---|---|
| LMArena Vision | — | 1297 |
| Blueprint-Bench 2 | — | 36.2% |
| Furniture Assembly | — | 44.2% |
| LMArena Document | — | 1486 |
Multilingual GPT-5.5 leads
GLM-5.1: 55.0 (#36), GPT-5.5: 56.4 (#20)
| Benchmark | GLM-5.1 | GPT-5.5 |
|---|---|---|
| LMArena Non-English | 1447 | 1467 |
| LMArena Chinese | 1515 | 1533 |
| LMArena French | 1474 | 1486 |
| LMArena German | 1465 | 1480 |
| LMArena Japanese | 1434 | 1498 |
| LMArena Korean | 1418 | 1460 |
| LMArena Russian | 1454 | 1473 |
| LMArena Spanish | 1469 | 1468 |
Instruction Following GPT-5.5 leads
GLM-5.1: 76.3 (#42), GPT-5.5: 77.5 (#18)
| Benchmark | GLM-5.1 | GPT-5.5 |
|---|---|---|
| LMArena Instruction Following | 1451 | 1479 |
Long Context GPT-5.5 leads
GLM-5.1: 44.9 (#53), GPT-5.5: 48.3 (#12)
| Benchmark | GLM-5.1 | GPT-5.5 |
|---|---|---|
| LMArena Longer Query | 1466 | 1484 |
| CL-bench Life | — | 22.2% |
Writing & Preference GPT-5.5 leads
GLM-5.1: 66.9 (#31), GPT-5.5: 72.7 (#13)
| Benchmark | GLM-5.1 | GPT-5.5 |
|---|---|---|
| LMArena Text | 1461 | 1472 |
| LMArena Creative Writing | 1453 | 1455 |
| EQ-Bench Creative Writing | 1592 | 1844 |
| LMArena Multi-Turn | 1472 | 1476 |
| EQ-Bench 4 | — | 1315 |
Frequently asked questions
Is GLM-5.1 better than GPT-5.5?
GPT-5.5 is the stronger model overall, scoring 63.4 to 47.8 on the Noometry Index. GLM-5.1 costs 5.2× less per token, which makes it the better buy when GPT-5.5's lead doesn't matter for your workload.
Which is cheaper, GLM-5.1 or GPT-5.5?
GLM-5.1 is cheaper. It lists at $1.40 per million input tokens and $4.40 per million output tokens; GPT-5.5 lists at $5 and $30.
Is GLM-5.1 or GPT-5.5 better for coding?
GPT-5.5 scores higher on coding benchmarks: 58.2 versus 48.7 in the Noometry coding category.
Which has the bigger context window?
GPT-5.5 does, with 1.05M tokens against 200K.
How many benchmarks do GLM-5.1 and GPT-5.5 share?
40 benchmarks have published results for both models. GLM-5.1 has 41 scored results on Noometry and GPT-5.5 has 71.