# GPT-5.5 Pro vs Grok 4.20 (Non-Reasoning)

> GPT-5.5 Pro is the stronger model overall, scoring 64.3 to 48.6 on the Noometry Index. Grok 4.20 (Non-Reasoning) costs 43× less per token, which makes it the better buy when GPT-5.5 Pro's lead doesn't matter for your workload.

- Canonical page: https://noometry.com/compare/gpt-5-5-pro-vs-grok-4-20
- Last updated: 2026-10-12
- Shared benchmarks: 10

## Summary

- They share 10 benchmarks with published results for both. GPT-5.5 Pro scores higher in 3 categories and Grok 4.20 (Non-Reasoning) in 0 categories; 3 gaps are clear of the uncertainty.
- The widest gap is in math, where GPT-5.5 Pro leads 84.0 to 48.2.
- The biggest single-benchmark swing is FrontierMath Tier 4: 78% for GPT-5.5 Pro and 17.1% for Grok 4.20 (Non-Reasoning).
- Grok 4.20 (Non-Reasoning) is cheaper at $1.25 / $2.50 per million input/output tokens, against $30 / $180 for GPT-5.5 Pro.
- GPT-5.5 Pro accepts more context: 1.05M tokens versus 1M.

## Snapshot

| | GPT-5.5 Pro | Grok 4.20 (Non-Reasoning) |
|---|---|---|
| Provider | OpenAI | xAI |
| Noometry Index | 64.3 | 48.6 |
| Rank | 8 | 54 |
| Context | 1.05M | 1M |
| Input $/M | $30 | $1.25 |
| Output $/M | $180 | $2.50 |
| Weights | Proprietary | Proprietary |

## Coding

- GPT-5.5 Pro: —
- Grok 4.20 (Non-Reasoning): 42.1 (#112)

| Benchmark | GPT-5.5 Pro | Grok 4.20 (Non-Reasoning) |
|---|---|---|
| LMArena WebDev | — | 1375 |
| WeirdML | — | 52.3% |
| LMArena Coding | — | 1459 |
| ALE-Bench | — | 1,150 |

## Agentic & Tool Use

- GPT-5.5 Pro: —
- Grok 4.20 (Non-Reasoning): 34.4 (#46)

| Benchmark | GPT-5.5 Pro | Grok 4.20 (Non-Reasoning) |
|---|---|---|
| Terminal-Bench | — | 57.3% |
| τ²-bench Banking | — | 18% |
| LMArena Search | — | 1189 |
| Vending-Bench 2 | — | 4,663 |

## Reasoning

- GPT-5.5 Pro: 73.3 (#10)
- Grok 4.20 (Non-Reasoning): 52.3 (#32)

| Benchmark | GPT-5.5 Pro | Grok 4.20 (Non-Reasoning) |
|---|---|---|
| ARC-AGI-2 | 84.6% | 65.1% |
| ARC-AGI-1 | 96.5% | 89.5% |
| Chess Puzzles | 64% | 24% |
| DTBench | 96% | 90.1% |
| LMCA | 53.9% | 38.7% |
| Epoch Capabilities Index | 162.07 | 151.98 |
| SimpleBench | 76.9% | — |
| Kagi LLM Benchmark | — | 75% |
| NYT Connections (extended) | — | 85.4% |
| CritPt | 30.6% | — |
| Thematic Generalization | — | 63.8% |
| LMArena Hard Prompts | — | 1451 |
| ForecastBench | — | 61.4 |

## Math

- GPT-5.5 Pro: 84.0 (#10)
- Grok 4.20 (Non-Reasoning): 48.2 (#65)

| Benchmark | GPT-5.5 Pro | Grok 4.20 (Non-Reasoning) |
|---|---|---|
| FrontierMath (Tiers 1-3) | 87.7% | 44.9% |
| FrontierMath Tier 4 | 78% | 17.1% |
| OTIS Mock AIME 2024-2025 | 100% | 92.2% |
| ProofBench | — | 14% |
| LMArena Math | — | 1455 |
| FrontierMath (Feb 2025 set) | 52.4% | — |
| FrontierMath Tier 4 (v1) | 39.6% | — |

## Knowledge

- GPT-5.5 Pro: 64.1 (#19)
- Grok 4.20 (Non-Reasoning): 52.8 (#60)

| Benchmark | GPT-5.5 Pro | Grok 4.20 (Non-Reasoning) |
|---|---|---|
| GPQA Diamond | 93.9% | 89.3% |
| SimpleQA Verified | — | 30.2% |
| LMArena Expert | — | 1439 |

## Multimodal

- GPT-5.5 Pro: —
- Grok 4.20 (Non-Reasoning): 33.3 (#98)

| Benchmark | GPT-5.5 Pro | Grok 4.20 (Non-Reasoning) |
|---|---|---|
| LMArena Vision | — | 1263 |
| Blueprint-Bench 2 | — | 0% |
| LMArena Document | — | 1416 |

## Multilingual

- GPT-5.5 Pro: —
- Grok 4.20 (Non-Reasoning): 54.5 (#40)

| Benchmark | GPT-5.5 Pro | Grok 4.20 (Non-Reasoning) |
|---|---|---|
| LMArena Non-English | — | 1441 |
| LMArena Chinese | — | 1481 |
| LMArena French | — | 1476 |
| LMArena German | — | 1465 |
| LMArena Japanese | — | 1449 |
| LMArena Korean | — | 1417 |
| LMArena Russian | — | 1458 |
| LMArena Spanish | — | 1443 |

## Instruction Following

- GPT-5.5 Pro: —
- Grok 4.20 (Non-Reasoning): 74.8 (#83)

| Benchmark | GPT-5.5 Pro | Grok 4.20 (Non-Reasoning) |
|---|---|---|
| LMArena Instruction Following | — | 1420 |

## Long Context

- GPT-5.5 Pro: —
- Grok 4.20 (Non-Reasoning): 45.5 (#34)

| Benchmark | GPT-5.5 Pro | Grok 4.20 (Non-Reasoning) |
|---|---|---|
| CL-bench | — | 22.2% |
| CL-bench Life | — | 11.9% |
| LMArena Longer Query | — | 1437 |

## Writing & Preference

- GPT-5.5 Pro: —
- Grok 4.20 (Non-Reasoning): 65.7 (#44)

| Benchmark | GPT-5.5 Pro | Grok 4.20 (Non-Reasoning) |
|---|---|---|
| LMArena Text | — | 1451 |
| LMArena Creative Writing | — | 1438 |
| EQ-Bench Creative Writing | — | 1574 |
| LMArena Multi-Turn | — | 1456 |

## FAQ

### Is GPT-5.5 Pro better than Grok 4.20 (Non-Reasoning)?

GPT-5.5 Pro is the stronger model overall, scoring 64.3 to 48.6 on the Noometry Index. Grok 4.20 (Non-Reasoning) costs 43× 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-5.5 Pro or Grok 4.20 (Non-Reasoning)?

Grok 4.20 (Non-Reasoning) is cheaper. It lists at $1.25 per million input tokens and $2.50 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 1M.

### How many benchmarks do GPT-5.5 Pro and Grok 4.20 (Non-Reasoning) share?

10 benchmarks have published results for both models. GPT-5.5 Pro has 14 scored results on Noometry and Grok 4.20 (Non-Reasoning) has 46.