# GPT-5.5 Pro vs Mercury 2.5

> GPT-5.5 Pro is the stronger model overall, scoring 64.3 to 33.5 on the Noometry Index. Mercury 2.5 costs 1000× 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-2-5
- Last updated: 2026-10-12
- Shared benchmarks: 1

## Summary

- They share 1 benchmark with published results for both. GPT-5.5 Pro scores higher in 2 categories and Mercury 2.5 in 0 categories; 2 gaps are clear of the uncertainty.
- The widest gap is in math, where GPT-5.5 Pro leads 84.0 to 23.3.
- The biggest single-benchmark swing is CritPt: 30.6% for GPT-5.5 Pro and 0% for Mercury 2.5.
- Mercury 2.5 is cheaper at $0.04 / $0.15 per million input/output tokens, against $30 / $180 for GPT-5.5 Pro.
- GPT-5.5 Pro accepts more context: 1.05M tokens versus 260K.

## Snapshot

| | GPT-5.5 Pro | Mercury 2.5 |
|---|---|---|
| Provider | OpenAI | Inception |
| Noometry Index | 64.3 | 33.5 |
| Rank | 8 | 242 |
| Context | 1.05M | 260K |
| Input $/M | $30 | $0.04 |
| Output $/M | $180 | $0.15 |
| Weights | Proprietary | Proprietary |

## Coding

- GPT-5.5 Pro: —
- Mercury 2.5: 39.5 (#156)

| Benchmark | GPT-5.5 Pro | Mercury 2.5 |
|---|---|---|
| SciCode | — | 38.5% |
| ALE-Bench | — | 301.65 |

## Reasoning

- GPT-5.5 Pro: 73.3 (#10)
- Mercury 2.5: 22.4 (#193)

| Benchmark | GPT-5.5 Pro | Mercury 2.5 |
|---|---|---|
| CritPt | 30.6% | 0% |
| ARC-AGI-2 | 84.6% | — |
| SimpleBench | 76.9% | — |
| ARC-AGI-1 | 96.5% | — |
| Chess Puzzles | 64% | — |
| DTBench | 96% | — |
| LMCA | 53.9% | — |
| Epoch Capabilities Index | 162.07 | — |

## Math

- GPT-5.5 Pro: 84.0 (#10)
- Mercury 2.5: 23.3 (#272)

| Benchmark | GPT-5.5 Pro | Mercury 2.5 |
|---|---|---|
| FrontierMath (Tiers 1-3) | 87.7% | — |
| FrontierMath Tier 4 | 78% | — |
| OTIS Mock AIME 2024-2025 | 100% | — |
| ProofBench | — | 3% |
| FrontierMath (Feb 2025 set) | 52.4% | — |
| FrontierMath Tier 4 (v1) | 39.6% | — |

## Knowledge

- GPT-5.5 Pro: 64.1 (#19)
- Mercury 2.5: —

| Benchmark | GPT-5.5 Pro | Mercury 2.5 |
|---|---|---|
| GPQA Diamond | 93.9% | — |

## FAQ

### Is GPT-5.5 Pro better than Mercury 2.5?

GPT-5.5 Pro is the stronger model overall, scoring 64.3 to 33.5 on the Noometry Index. Mercury 2.5 costs 1000× 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 2.5?

Mercury 2.5 is cheaper. It lists at $0.04 per million input tokens and $0.15 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 260K.

### How many benchmarks do GPT-5.5 Pro and Mercury 2.5 share?

1 benchmark has published results for both models. GPT-5.5 Pro has 14 scored results on Noometry and Mercury 2.5 has 4.