# GPT-5.5 Pro vs Mercury 2

> GPT-5.5 Pro is the stronger model overall, scoring 64.3 to 38.8 on the Noometry Index. Mercury 2 costs 180× 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-mercury-2
- Last updated: 2026-10-10
- Shared benchmarks: 1

## Summary

- They share 1 benchmark with published results for both. GPT-5.5 Pro scores higher in 2 categories and Mercury 2 in 0 categories; 2 gaps are clear of the uncertainty.
- The widest gap is in reasoning, where GPT-5.5 Pro leads 73.6 to 23.0.
- The biggest single-benchmark swing is CritPt: 30.6% for GPT-5.5 Pro and 0.8% for Mercury 2.
- Mercury 2 is cheaper at $0.25 / $0.75 per million input/output tokens, against $30 / $180 for GPT-5.5 Pro.
- GPT-5.5 Pro accepts more context: 1.05M tokens versus 128K.

## Snapshot

| | GPT-5.5 Pro | Mercury 2 |
|---|---|---|
| Provider | OpenAI | Inception |
| Noometry Index | 64.3 | 38.8 |
| Rank | 7 | 167 |
| Context | 1.05M | 128K |
| Input $/M | $30 | $0.25 |
| Output $/M | $180 | $0.75 |
| Weights | Proprietary | Proprietary |

## Coding

- GPT-5.5 Pro: —
- Mercury 2: 33.2 (#250)

| Benchmark | GPT-5.5 Pro | Mercury 2 |
|---|---|---|
| LMArena WebDev | — | 1170 |
| SciCode | — | 38.7% |
| WeirdML | — | 43.2% |
| LMArena Coding | — | 1391 |
| ALE-Bench | — | 785.58 |

## Reasoning

- GPT-5.5 Pro: 73.6 (#7)
- Mercury 2: 23.0 (#170)

| Benchmark | GPT-5.5 Pro | Mercury 2 |
|---|---|---|
| CritPt | 30.6% | 0.8% |
| ARC-AGI-2 | 84.6% | — |
| SimpleBench | 76.9% | — |
| ARC-AGI-1 | 96.5% | — |
| Chess Puzzles | 64% | — |
| LMArena Hard Prompts | — | 1362 |
| DTBench | 96% | — |
| LMCA | 53.9% | — |
| Epoch Capabilities Index | 162.45 | — |

## Math

- GPT-5.5 Pro: 83.8 (#8)
- Mercury 2: —

| Benchmark | GPT-5.5 Pro | Mercury 2 |
|---|---|---|
| FrontierMath (Tiers 1-3) | 87.7% | — |
| FrontierMath Tier 4 | 78% | — |
| OTIS Mock AIME 2024-2025 | 100% | — |
| FrontierMath (Feb 2025 set) | 52.4% | — |
| FrontierMath Tier 4 (v1) | 39.6% | — |

## Knowledge

- GPT-5.5 Pro: 64.2 (#17)
- Mercury 2: 35.6 (#170)

| Benchmark | GPT-5.5 Pro | Mercury 2 |
|---|---|---|
| GPQA Diamond | 93.9% | — |
| Vectara Hallucination Rate | — | 12.3% |
| LMArena Expert | — | 1358 |

## Multilingual

- GPT-5.5 Pro: —
- Mercury 2: 46.8 (#153)

| Benchmark | GPT-5.5 Pro | Mercury 2 |
|---|---|---|
| LMArena Non-English | — | 1331 |
| LMArena Chinese | — | 1416 |
| LMArena Russian | — | 1303 |

## Instruction Following

- GPT-5.5 Pro: —
- Mercury 2: 70.4 (#161)

| Benchmark | GPT-5.5 Pro | Mercury 2 |
|---|---|---|
| LMArena Instruction Following | — | 1328 |

## Long Context

- GPT-5.5 Pro: —
- Mercury 2: 40.4 (#149)

| Benchmark | GPT-5.5 Pro | Mercury 2 |
|---|---|---|
| LMArena Longer Query | — | 1329 |

## Writing & Preference

- GPT-5.5 Pro: —
- Mercury 2: 54.0 (#151)

| Benchmark | GPT-5.5 Pro | Mercury 2 |
|---|---|---|
| LMArena Text | — | 1355 |
| LMArena Creative Writing | — | 1289 |
| LMArena Multi-Turn | — | 1358 |

## FAQ

### Is GPT-5.5 Pro better than Mercury 2?

GPT-5.5 Pro is the stronger model overall, scoring 64.3 to 38.8 on the Noometry Index. Mercury 2 costs 180× 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 Mercury 2?

Mercury 2 is cheaper. It lists at $0.25 per million input tokens and $0.75 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 128K.

### How many benchmarks do GPT-5.5 Pro and Mercury 2 share?

1 benchmark has published results for both models. GPT-5.5 Pro has 14 scored results on Noometry and Mercury 2 has 17.