# GPT-5.1 vs GPT-5.5 Pro

> Side-by-side benchmark comparison for GPT-5.1 and GPT-5.5 Pro across agentic, coding, multimodal, knowledge, reasoning, multilingual, and math tasks.

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

- Shared sourced benchmarks: 2
- HTML indexing: indexable
- Ranking lane: BenchAlign v5

## Quick Verdict

Evidence is too thin for a benchmark verdict: GPT-5.1 and GPT-5.5 Pro share only 2 sourced benchmark rows.

## Summary

- Only 2 shared sourced benchmark rows are available. That is not enough for a broad capability verdict, so this mirror does not name an overall winner.
- GPT-5.1 has the lower published output-token price.
- GPT-5.5 Pro has the larger published context window at 1M.

## Model Snapshot

| Property | GPT-5.1 | GPT-5.5 Pro |
|----------|----------|----------|
| Creator | OpenAI | OpenAI |
| Type | Proprietary | Proprietary |
| Reasoning | Reasoning | Reasoning |
| Context | 200K | 1M |
| Independent public score (not head-to-head) | 63.68 | 63.07 |
| Benchmarks Covered | 4 | 6 |
| Pricing (input/output) | $1.25 / $10.00 | $30.00 / $180.00 |

## Category Breakdown

### Agentic

- Winner: Insufficient shared evidence
- GPT-5.1 public-lane score: 56.3 (Estimated · #36/151)
- GPT-5.5 Pro public-lane score: 60.6 (Estimated · #24/151)

| Benchmark | GPT-5.1 | GPT-5.5 Pro | Winner |
|-----------|-----------|-----------|--------|
| Gert Labs | 41.24% | Coming soon | Coming soon |
| BrowseComp | Coming soon | 90.1% | Coming soon |

### Coding

- Winner: Insufficient shared evidence
- GPT-5.1 public-lane score: 45.2 (Supported · #109/183)
- GPT-5.5 Pro public-lane score: Coming soon

| Benchmark | GPT-5.1 | GPT-5.5 Pro | Winner |
|-----------|-----------|-----------|--------|
| Vibe Code Bench | 24.61% | Coming soon | Coming soon |

### Multimodal & Grounded

- Winner: Insufficient shared evidence
- GPT-5.1 public-lane score: 71.2 (Unranked · 1 rankable row)
- GPT-5.5 Pro public-lane score: Coming soon

### Reasoning

- Winner: Insufficient shared evidence
- GPT-5.1 public-lane score: 76.2 (Unranked · 2 rankable rows)
- GPT-5.5 Pro public-lane score: Coming soon

### Knowledge

- Winner: Insufficient shared evidence
- GPT-5.1 public-lane score: 58.8 (Estimated · #43/181)
- GPT-5.5 Pro public-lane score: 61.1 (Estimated · #36/181)

| Benchmark | GPT-5.1 | GPT-5.5 Pro | Winner |
|-----------|-----------|-----------|--------|
| HLE | Coming soon | 57.2% | Coming soon |
| HLE w/o tools | Coming soon | 43.1% | Coming soon |

### Instruction Following

- Winner: Insufficient shared evidence
- GPT-5.1 public-lane score: 89.1 (#26/120)
- GPT-5.5 Pro public-lane score: Coming soon

### Mathematics

- Winner: Insufficient shared evidence
- GPT-5.1 public-lane score: 49.2 (Unranked · 2 rankable rows)
- GPT-5.5 Pro public-lane score: 70.2 (Unranked · 3 rankable rows)

| Benchmark | GPT-5.1 | GPT-5.5 Pro | Winner |
|-----------|-----------|-----------|--------|
| FrontierMath v2 (Tiers 1-3) | 31.034% | 51.000% | GPT-5.5 Pro |
| FrontierMath v2 (Tier 4) | 12.500% | 39.600% | GPT-5.5 Pro |
| FrontierMath (legacy) | Coming soon | 52.4% | Coming soon |

## FAQ

### Is there enough evidence to pick between GPT-5.1 and GPT-5.5 Pro?

Not yet. The models share only 2 sourced benchmark rows, 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 GPT-5.5](/compare/gpt-5-1-vs-gpt-5-5)
- [GPT-5.5 Pro vs GPT-5.5](/compare/gpt-5-5-vs-gpt-5-5-pro)
- [GPT-5.1 vs Claude Fable 5.1](/compare/claude-fable-5-1-vs-gpt-5-1)
- [GPT-5.5 Pro vs Claude Fable 5.1](/compare/claude-fable-5-1-vs-gpt-5-5-pro)

## Explore More

- [GPT-5.1 profile](/models/gpt-5-1)
- [GPT-5.5 Pro profile](/models/gpt-5-5-pro)
- [Compare Pricing](/llm-pricing)
- [Alternative Finder](/tools/alternative-finder)
- [LLM Selector](/tools/llm-selector)
- [Overall Rankings](/best/overall)