# Gemini 3.8 Flash vs Grok 4.20

> Side-by-side benchmark comparison for Gemini 3.8 Flash and Grok 4.20 across agentic, coding, multimodal, knowledge, reasoning, multilingual, and math tasks.

- Canonical page: https://benchlm.ai/compare/gemini-3-8-flash-vs-grok-4-20-beta
- Last updated: October 17, 2026

- Shared sourced benchmarks: 8
- HTML indexing: indexable
- Ranking lane: BenchAlign v5.8

## Quick Verdict

Gemini 3.8 Flash leads by point estimate. Conditional score ranges do not establish rank confidence. Choose using the category evidence and your own workload tests.

## Summary

- Gemini 3.8 Flash has the higher overall point estimate 69.25 to 57.43. Conditional score ranges do not establish rank confidence.
- The clearest category separation is in agentic, where the averages are 65.9 for Gemini 3.8 Flash and 25.1 for Grok 4.20.
- The biggest single benchmark swing is Terminal-Bench 2.1 (Vals) in Agentic, with scores of 81.3% and 44.2%.
- Grok 4.20 is the cheaper option on output tokens, which matters if you expect large responses or heavy interactive use.
- Grok 4.20 also has the larger context window at 2M.

## Model Snapshot

| Property | Gemini 3.8 Flash | Grok 4.20 |
|----------|----------|----------|
| Creator | Google | xAI |
| Type | Proprietary | Proprietary |
| Reasoning | Reasoning | Reasoning |
| Context | 1M | 2M |
| Overall Score | 69.25 | 57.43 |
| Benchmarks Covered | 31 | 24 |
| Pricing (input/output) | $0.75 / $3.75 | $1.25 / $2.50 |

## Category Breakdown

### Agentic

- Winner: Gemini 3.8 Flash
- Gemini 3.8 Flash public-lane score: 65.9 (Supported · #16/128)
- Grok 4.20 public-lane score: 25.1 (Supported · #103/128)

| Benchmark | Gemini 3.8 Flash | Grok 4.20 | Winner |
|-----------|-----------|-----------|--------|
| Finance Agent v2 | 61.4% | Coming soon | Coming soon |
| Terminal-Bench 2.1 | 89.4% | Coming soon | Coming soon |
| Terminal-Bench 4.0 | 19.10% | Coming soon | Coming soon |
| OSWorld 2.0 | 59.0% | Coming soon | Coming soon |
| Terminal-Bench 2.1 (Vals) | 81.3% | 44.2% | Gemini 3.8 Flash |
| ApprenticeBench | 24% | Coming soon | Coming soon |
| Hermes Index | 38.1% | Coming soon | Coming soon |
| Hermes Bench | 62.2% | Coming soon | Coming soon |
| MazeBench | 4% | 0% | Gemini 3.8 Flash |
| Terminal-Bench 2.0 | Coming soon | 47.1% | Coming soon |
| DeepSearchQA | Coming soon | 62.8% | Coming soon |
| Gert Labs | Coming soon | 38.36% | Coming soon |

### Coding

- Winner: Gemini 3.8 Flash
- Gemini 3.8 Flash public-lane score: 61 (Supported · #17/150)
- Grok 4.20 public-lane score: 21.6 (Supported · #118/150)

| Benchmark | Gemini 3.8 Flash | Grok 4.20 | Winner |
|-----------|-----------|-----------|--------|
| DeepSWE | 73.8% | Coming soon | Coming soon |
| Terminal-Bench 2.1 | 89.4% | Coming soon | Coming soon |
| CursorBench 3.2 | 69.2% | Coming soon | Coming soon |
| LiveCodeBench (Vals) | 89.5% | 84.3% | Gemini 3.8 Flash |
| SWE-bench (Vals) | 80.0% | 72.2% | Gemini 3.8 Flash |
| FrontierSWE v2 | 19.6% | Coming soon | Coming soon |
| CursorBench 4.0 | 39.6% | Coming soon | Coming soon |
| Bug Hunt Bench | 18.0 fixes | Coming soon | Coming soon |
| LiveCodeBench Pro | Coming soon | 74.2% | Coming soon |
| SWE-bench Verified | Coming soon | 76.7% | Coming soon |
| SWE-bench Pro | Coming soon | 51.8% | Coming soon |
| Vibe Code Bench | Coming soon | 4.06% | Coming soon |

### Reasoning

- Winner: Not comparable
- Gemini 3.8 Flash public-lane score: 74.3 (#17/28)
- Grok 4.20 public-lane score: 44.9 (Unranked · 2 rankable rows)

| Benchmark | Gemini 3.8 Flash | Grok 4.20 | Winner |
|-----------|-----------|-----------|--------|
| ARC-AGI-1 | 98.50% | Coming soon | Coming soon |
| ARC-AGI-2 | 89.2% | 53.3% | Gemini 3.8 Flash |
| ARC-AGI-3 | 10.4% | 0.1% | Gemini 3.8 Flash |

### Multimodal & Grounded

- Winner: Directional only
- Gemini 3.8 Flash public-lane score: 87.3 (#9/54)
- Grok 4.20 public-lane score: 53.4 (#47/54)

| Benchmark | Gemini 3.8 Flash | Grok 4.20 | Winner |
|-----------|-----------|-----------|--------|
| CharXiv w/o tools | 86.2% | Coming soon | Coming soon |
| LVBench | 87.1% | Coming soon | Coming soon |
| MMMU-Pro | Coming soon | 75.2% | Coming soon |
| CharXiv | Coming soon | 60.9% | Coming soon |
| ERQA | Coming soon | 54.1% | Coming soon |
| SimpleVQA | Coming soon | 57.4% | Coming soon |
| MedXpertQA (MM) | Coming soon | 65.8% | Coming soon |

### Knowledge

- Winner: Gemini 3.8 Flash
- Gemini 3.8 Flash public-lane score: 73.5 (Supported · #13/184)
- Grok 4.20 public-lane score: 53.1 (Supported · #69/184)

| Benchmark | Gemini 3.8 Flash | Grok 4.20 | Winner |
|-----------|-----------|-----------|--------|
| HLE-Verified | 54.9% | Coming soon | Coming soon |
| LABBench2 | 86.2% | Coming soon | Coming soon |
| BioMysteryBench (human-solvable) | 88.8% | Coming soon | Coming soon |
| BioMysteryBench (human-difficult) | 56.5% | Coming soon | Coming soon |
| GPQA Diamond (Vals) | 94.4% | 88.6% | Gemini 3.8 Flash |
| MMLU-Pro (Vals) | 90.2% | 86.3% | Gemini 3.8 Flash |
| GPQA-D | Coming soon | 88.5% | Coming soon |
| HLE w/o tools | Coming soon | 31.6% | Coming soon |
| HealthBench Hard | Coming soon | 20.3% | Coming soon |
| MedXpertQA (Text) | Coming soon | 50.2% | Coming soon |

### Instruction Following

- Winner: Not comparable
- Gemini 3.8 Flash public-lane score: Coming soon
- Grok 4.20 public-lane score: Coming soon

| Benchmark | Gemini 3.8 Flash | Grok 4.20 | Winner |
|-----------|-----------|-----------|--------|
| Gray Swan IPI (15 attempts) | 5.5% | Coming soon | Coming soon |

### Mathematics

- Winner: Not comparable
- Gemini 3.8 Flash public-lane score: 69.7 (Unranked · 2 rankable rows)
- Grok 4.20 public-lane score: Coming soon

| Benchmark | Gemini 3.8 Flash | Grok 4.20 | Winner |
|-----------|-----------|-----------|--------|
| FrontierMath v2 (Tiers 1-3) | 68.421% | Coming soon | Coming soon |
| FrontierMath v2 (Tier 4) | 21.951% | Coming soon | Coming soon |

## FAQ

### Which is better overall, Gemini 3.8 Flash or Grok 4.20?

Gemini 3.8 Flash has the higher overall point estimate. Conditional score ranges do not establish rank confidence.

### Where is the biggest gap between Gemini 3.8 Flash and Grok 4.20?

The widest category gap is in agentic, where the averages are 65.9 for Gemini 3.8 Flash and 25.1 for Grok 4.20.

### How many benchmarks does Gemini 3.8 Flash cover on BenchLM?

Gemini 3.8 Flash currently has 31 sourced benchmark scores on BenchLM.

### How many benchmarks does Grok 4.20 cover on BenchLM?

Grok 4.20 currently has 24 sourced benchmark scores on BenchLM.

## Related Comparisons

- [Gemini 3.8 Flash vs Gemini 3.8 Flash Cyber](/compare/gemini-3-8-flash-vs-gemini-3-8-flash-cyber)
- [Grok 4.20 vs Gemini 3.8 Flash Cyber](/compare/gemini-3-8-flash-cyber-vs-grok-4-20-beta)
- [Gemini 3.8 Flash vs Grok 4.20 Multi-agent](/compare/gemini-3-8-flash-vs-grok-4-20-multi-agent-beta)
- [Grok 4.20 vs Grok 4.20 Multi-agent](/compare/grok-4-20-beta-vs-grok-4-20-multi-agent-beta)

## Explore More

- [Gemini 3.8 Flash profile](/models/gemini-3-8-flash)
- [Grok 4.20 profile](/models/grok-4-20-beta)
- [Compare Pricing](/llm-pricing)
- [Alternative Finder](/tools/alternative-finder)
- [LLM Selector](/tools/llm-selector)
- [Overall Rankings](/best/overall)