# GPT-5.1 vs Grok 4.1 Fast (Reasoning)

> Side-by-side benchmark comparison for GPT-5.1 and Grok 4.1 Fast (Reasoning) across agentic, coding, multimodal, knowledge, reasoning, multilingual, and math tasks.

- Canonical page: https://benchlm.ai/compare/gpt-5-1-vs-grok-4-1-fast-reasoning
- Last updated: September 4, 2026

- Shared sourced benchmarks: 1
- HTML indexing: indexable
- Ranking lane: BenchAlign v5

## Quick Verdict

Evidence is too thin for a benchmark verdict: GPT-5.1 and Grok 4.1 Fast (Reasoning) share only 1 sourced benchmark row.

## Summary

- Only 1 shared sourced benchmark row is available. That is not enough for a broad capability verdict, so this mirror does not name an overall winner.
- Grok 4.1 Fast (Reasoning) has the larger published context window at 2M.

## Model Snapshot

| Property | GPT-5.1 | Grok 4.1 Fast (Reasoning) |
|----------|----------|----------|
| Creator | OpenAI | xAI |
| Type | Proprietary | Proprietary |
| Reasoning | Reasoning | Reasoning |
| Context | 200K | 2M |
| Independent public score (not head-to-head) | 63.68 | 58.18 |
| Benchmarks Covered | 4 | 1 |
| Pricing (input/output) | $1.25 / $10.00 | N/A |

## Category Breakdown

### Agentic

- Winner: Insufficient shared evidence
- GPT-5.1 public-lane score: 56.3 (Estimated · #36/151)
- Grok 4.1 Fast (Reasoning) public-lane score: Coming soon

| Benchmark | GPT-5.1 | Grok 4.1 Fast (Reasoning) | Winner |
|-----------|-----------|-----------|--------|
| Gert Labs | 41.24% | Coming soon | Coming soon |

### Coding

- Winner: Insufficient shared evidence
- GPT-5.1 public-lane score: 45.2 (Supported · #109/183)
- Grok 4.1 Fast (Reasoning) public-lane score: 48.7 (Estimated · #85/183)

| Benchmark | GPT-5.1 | Grok 4.1 Fast (Reasoning) | Winner |
|-----------|-----------|-----------|--------|
| Vibe Code Bench | 24.61% | 1.20% | GPT-5.1 |

### Multimodal & Grounded

- Winner: Insufficient shared evidence
- GPT-5.1 public-lane score: 71.2 (Unranked · 1 rankable row)
- Grok 4.1 Fast (Reasoning) public-lane score: 53.3 (Unranked · 1 rankable row)

### Reasoning

- Winner: Insufficient shared evidence
- GPT-5.1 public-lane score: 76.2 (Unranked · 2 rankable rows)
- Grok 4.1 Fast (Reasoning) public-lane score: 71.6 (Unranked · 2 rankable rows)

### Knowledge

- Winner: Insufficient shared evidence
- GPT-5.1 public-lane score: 58.8 (Estimated · #43/181)
- Grok 4.1 Fast (Reasoning) public-lane score: 51.5 (Estimated · #82/181)

### Instruction Following

- Winner: Insufficient shared evidence
- GPT-5.1 public-lane score: 89.1 (#26/120)
- Grok 4.1 Fast (Reasoning) public-lane score: 62.8 (#69/120)

### Mathematics

- Winner: Insufficient shared evidence
- GPT-5.1 public-lane score: 49.2 (Unranked · 2 rankable rows)
- Grok 4.1 Fast (Reasoning) public-lane score: Coming soon

| Benchmark | GPT-5.1 | Grok 4.1 Fast (Reasoning) | Winner |
|-----------|-----------|-----------|--------|
| FrontierMath v2 (Tiers 1-3) | 31.034% | Coming soon | Coming soon |
| FrontierMath v2 (Tier 4) | 12.500% | Coming soon | Coming soon |

## FAQ

### Is there enough evidence to pick between GPT-5.1 and Grok 4.1 Fast (Reasoning)?

Not yet. The models share only 1 sourced benchmark row, so this mirror reports the available measurements and metadata without naming a broad winner.

### What can I compare safely on this page?

Published pricing, context windows, model type, and individual shared benchmark rows are directly comparable. Independent overall scores and non-overlapping benchmark coverage are labeled separately and should not be read as a controlled head-to-head result.

## Related Comparisons

- [GPT-5.1 vs Grok 4.1 Fast](/compare/gpt-5-1-vs-grok-4-1-fast)
- [Grok 4.1 Fast (Reasoning) vs Grok 4.1 Fast](/compare/grok-4-1-fast-vs-grok-4-1-fast-reasoning)
- [GPT-5.1 vs Claude Fable 5.1](/compare/claude-fable-5-1-vs-gpt-5-1)
- [Grok 4.1 Fast (Reasoning) vs Claude Fable 5.1](/compare/claude-fable-5-1-vs-grok-4-1-fast-reasoning)

## Explore More

- [GPT-5.1 profile](/models/gpt-5-1)
- [Grok 4.1 Fast (Reasoning) profile](/models/grok-4-1-fast-reasoning)
- [Compare Pricing](/llm-pricing)
- [Alternative Finder](/tools/alternative-finder)
- [LLM Selector](/tools/llm-selector)
- [Overall Rankings](/best/overall)