Model comparison
GLM-4.5-Air vs GLM-5.1
GLM-5.1 is the stronger model overall, scoring 47.8 to 38.9 on the Noometry Index. GLM-4.5-Air costs 5.1× less per token, which makes it the better buy when GLM-5.1's lead doesn't matter for your workload.
Last verified . 17 shared benchmarks.
Summary
- They share 17 benchmarks with published results for both. GLM-4.5-Air scores higher in 0 categories and GLM-5.1 in 8 categories; 8 gaps are clear of the uncertainty.
- The widest gap is in knowledge, where GLM-5.1 leads 54.9 to 35.0.
- GLM-4.5-Air is cheaper at $0.20 / $1.10 per million input/output tokens, against $1.40 / $4.40 for GLM-5.1.
- GLM-5.1 accepts more context: 200K tokens versus 131K.
Side by side
| GLM-4.5-Air | GLM-5.1 | |
|---|---|---|
| Provider | Z.ai (Zhipu) | Z.ai (Zhipu) |
| Noometry Index | 38.9 | 47.8 |
| Released | 2025-07-20 | 2026-04-07 |
| Weights | Open | Open |
| Context window | 131K | 200K |
| Max output | 98K | 131K |
| Input $ / M tokens | $0.20 | $1.40 |
| Output $ / M tokens | $1.10 | $4.40 |
| Results tracked | 27 | 41 |
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Category by category
Coding GLM-5.1 leads
GLM-4.5-Air: 33.3 (#259), GLM-5.1: 48.7 (#55)
| Benchmark | GLM-4.5-Air | GLM-5.1 |
|---|---|---|
| LMArena Coding | 1397 | 1485 |
| SWE-bench Verified | — | 74.2% |
| LMArena WebDev | — | 1508 |
| SciCode | — | 43.8% |
| GSO | 2.9% | — |
| WeirdML | — | 57.1% |
| ALE-Bench | — | 887.1 |
Agentic & Tool Use Not comparable
GLM-4.5-Air: —, GLM-5.1: 24.9 (#113)
| Benchmark | GLM-4.5-Air | GLM-5.1 |
|---|---|---|
| APEX-Agents | — | 40.9% |
| ExploitBench | — | 18.1% |
| GBAEval | — | 0% |
| Vending-Bench 2 | — | 5,634 |
Reasoning GLM-5.1 leads
GLM-4.5-Air: 24.1 (#166), GLM-5.1: 39.1 (#60)
| Benchmark | GLM-4.5-Air | GLM-5.1 |
|---|---|---|
| LMArena Hard Prompts | 1379 | 1472 |
| SimpleBench | — | 55.1% |
| Kagi LLM Benchmark | 43% | — |
| NYT Connections (extended) | — | 77.7% |
| CritPt | — | 4.6% |
| Chess Puzzles | — | 19% |
| Thematic Generalization | — | 69.8% |
| Epoch Capabilities Index | — | 149.84 |
| ForecastBench | 59.2 | — |
Math GLM-5.1 leads
GLM-4.5-Air: 36.2 (#170), GLM-5.1: 49.7 (#60)
| Benchmark | GLM-4.5-Air | GLM-5.1 |
|---|---|---|
| LMArena Math | 1396 | 1473 |
| FrontierMath (Tiers 1-3) | — | 36.8% |
| MathArena Final-Answer Competitions | — | 67.1% |
| OTIS Mock AIME 2024-2025 | — | 93.3% |
| ProofBench | — | 22.2% |
| Omni-MATH | 39.1% | — |
| FrontierMath (Feb 2025 set) | — | 33.4% |
| FrontierMath Tier 4 (v1) | — | 12.5% |
Knowledge GLM-5.1 leads
GLM-4.5-Air: 35.0 (#191), GLM-5.1: 54.9 (#50)
| Benchmark | GLM-4.5-Air | GLM-5.1 |
|---|---|---|
| LMArena Expert | 1370 | 1476 |
| GPQA Diamond | — | 89.9% |
| Humanity's Last Exam | 8.1% | — |
| SimpleQA Verified | — | 34% |
| MMLU-Pro | 76.2% | — |
| Vectara Hallucination Rate | 9.3% | — |
| GPQA (HELM) | 59.4% | — |
Multilingual GLM-5.1 leads
GLM-4.5-Air: 49.1 (#135), GLM-5.1: 55.0 (#36)
| Benchmark | GLM-4.5-Air | GLM-5.1 |
|---|---|---|
| LMArena Non-English | 1366 | 1447 |
| LMArena Chinese | 1426 | 1515 |
| LMArena French | 1399 | 1474 |
| LMArena German | 1377 | 1465 |
| LMArena Japanese | 1348 | 1434 |
| LMArena Korean | 1308 | 1418 |
| LMArena Russian | 1373 | 1454 |
| LMArena Spanish | 1386 | 1469 |
Instruction Following GLM-5.1 leads
GLM-4.5-Air: 69.6 (#171), GLM-5.1: 76.3 (#42)
| Benchmark | GLM-4.5-Air | GLM-5.1 |
|---|---|---|
| LMArena Instruction Following | 1354 | 1451 |
| IFEval | 81.2% | — |
Long Context GLM-5.1 leads
GLM-4.5-Air: 41.6 (#135), GLM-5.1: 44.9 (#53)
| Benchmark | GLM-4.5-Air | GLM-5.1 |
|---|---|---|
| LMArena Longer Query | 1366 | 1466 |
Writing & Preference GLM-5.1 leads
GLM-4.5-Air: 55.9 (#139), GLM-5.1: 66.9 (#31)
| Benchmark | GLM-4.5-Air | GLM-5.1 |
|---|---|---|
| LMArena Text | 1384 | 1461 |
| LMArena Creative Writing | 1343 | 1453 |
| LMArena Multi-Turn | 1371 | 1472 |
| EQ-Bench Creative Writing | — | 1592 |
| WildBench | 78.9% | — |
Frequently asked questions
Is GLM-4.5-Air better than GLM-5.1?
GLM-5.1 is the stronger model overall, scoring 47.8 to 38.9 on the Noometry Index. GLM-4.5-Air costs 5.1× less per token, which makes it the better buy when GLM-5.1's lead doesn't matter for your workload.
Which is cheaper, GLM-4.5-Air or GLM-5.1?
GLM-4.5-Air is cheaper. It lists at $0.20 per million input tokens and $1.10 per million output tokens; GLM-5.1 lists at $1.40 and $4.40.
Is GLM-4.5-Air or GLM-5.1 better for coding?
GLM-5.1 scores higher on coding benchmarks: 48.7 versus 33.3 in the Noometry coding category.
Which has the bigger context window?
GLM-5.1 does, with 200K tokens against 131K.
How many benchmarks do GLM-4.5-Air and GLM-5.1 share?
17 benchmarks have published results for both models. GLM-4.5-Air has 27 scored results on Noometry and GLM-5.1 has 41.