# GLM-4.5-Air vs GLM-5.1

> GLM-5.1 is the stronger model overall, scoring 47.6 to 38.7 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.

- Canonical page: https://noometry.com/compare/glm-4-5-air-vs-glm-5-1
- Last updated: 2026-10-10
- Shared benchmarks: 17

## 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 55.0 to 34.6.
- 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.

## Snapshot

| | GLM-4.5-Air | GLM-5.1 |
|---|---|---|
| Provider | Z.ai (Zhipu) | Z.ai (Zhipu) |
| Noometry Index | 38.7 | 47.6 |
| Rank | 169 | 51 |
| Context | 131K | 200K |
| Input $/M | $0.20 | $1.40 |
| Output $/M | $1.10 | $4.40 |
| Weights | Open | Open |

## Coding

- GLM-4.5-Air: 34.5 (#225)
- GLM-5.1: 48.5 (#52)

| Benchmark | GLM-4.5-Air | GLM-5.1 |
|---|---|---|
| LMArena Coding | 1397 | 1486 |
| SWE-bench Verified | — | 74.2% |
| LMArena WebDev | — | 1509 |
| SciCode | — | 43.8% |
| GSO | 2.9% | — |
| WeirdML | — | 57.1% |
| ALE-Bench | — | 887.1 |

## Agentic & Tool Use

- GLM-4.5-Air: —
- GLM-5.1: 24.8 (#106)

| Benchmark | GLM-4.5-Air | GLM-5.1 |
|---|---|---|
| APEX-Agents | — | 40.9% |
| ExploitBench | — | 18.1% |
| GBAEval | — | 0% |
| Vending-Bench 2 | — | 5,634 |

## Reasoning

- GLM-4.5-Air: 23.3 (#166)
- GLM-5.1: 38.2 (#57)

| 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 | — | 149.86 |
| ForecastBench | 59.2 | — |

## Math

- GLM-4.5-Air: 33.8 (#166)
- GLM-5.1: 49.0 (#48)

| Benchmark | GLM-4.5-Air | GLM-5.1 |
|---|---|---|
| LMArena Math | 1396 | 1472 |
| 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-4.5-Air: 34.6 (#184)
- GLM-5.1: 55.0 (#45)

| Benchmark | GLM-4.5-Air | GLM-5.1 |
|---|---|---|
| LMArena Expert | 1370 | 1477 |
| 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-4.5-Air: 49.4 (#130)
- GLM-5.1: 55.2 (#34)

| Benchmark | GLM-4.5-Air | GLM-5.1 |
|---|---|---|
| LMArena Non-English | 1366 | 1448 |
| LMArena Chinese | 1427 | 1516 |
| LMArena French | 1399 | 1478 |
| LMArena German | 1376 | 1466 |
| LMArena Japanese | 1348 | 1436 |
| LMArena Korean | 1306 | 1423 |
| LMArena Russian | 1373 | 1453 |
| LMArena Spanish | 1385 | 1467 |

## Instruction Following

- GLM-4.5-Air: 69.8 (#165)
- GLM-5.1: 76.5 (#41)

| Benchmark | GLM-4.5-Air | GLM-5.1 |
|---|---|---|
| LMArena Instruction Following | 1353 | 1451 |
| IFEval | 81.2% | — |

## Long Context

- GLM-4.5-Air: 41.6 (#130)
- GLM-5.1: 44.9 (#51)

| Benchmark | GLM-4.5-Air | GLM-5.1 |
|---|---|---|
| LMArena Longer Query | 1367 | 1467 |

## Writing & Preference

- GLM-4.5-Air: 56.1 (#134)
- GLM-5.1: 67.2 (#29)

| Benchmark | GLM-4.5-Air | GLM-5.1 |
|---|---|---|
| LMArena Text | 1384 | 1462 |
| LMArena Creative Writing | 1343 | 1454 |
| LMArena Multi-Turn | 1371 | 1473 |
| EQ-Bench Creative Writing | — | 1592 |
| WildBench | 78.9% | — |

## FAQ

### Is GLM-4.5-Air better than GLM-5.1?

GLM-5.1 is the stronger model overall, scoring 47.6 to 38.7 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: 48.5 versus 34.5 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.