# gpt-oss-20b vs Mercury 2.5

> gpt-oss-20b and Mercury 2.5 score almost the same on the Noometry Index (32.5 vs 33.5), so choose on price, context window or the category you care about most.

- Canonical page: https://noometry.com/compare/gpt-oss-20b-vs-mercury-2-5
- Last updated: 2026-10-12
- Shared benchmarks: 3

## Summary

- They share 3 benchmarks with published results for both. gpt-oss-20b scores higher in 1 category and Mercury 2.5 in 2 categories; 3 gaps are clear of the uncertainty.
- The widest gap is in math, where gpt-oss-20b leads 39.4 to 23.3.
- gpt-oss-20b is cheaper at $0.018 / $0.09 per million input/output tokens, against $0.04 / $0.15 for Mercury 2.5.
- Mercury 2.5 accepts more context: 260K tokens versus 131K.
- gpt-oss-20b has downloadable open weights; the other is API-only.

## Snapshot

| | gpt-oss-20b | Mercury 2.5 |
|---|---|---|
| Provider | OpenAI | Inception |
| Noometry Index | 32.5 | 33.5 |
| Rank | 255 | 242 |
| Context | 131K | 260K |
| Input $/M | $0.018 | $0.04 |
| Output $/M | $0.09 | $0.15 |
| Weights | Open | Proprietary |

## Coding

- gpt-oss-20b: 37.6 (#192)
- Mercury 2.5: 39.5 (#156)

| Benchmark | gpt-oss-20b | Mercury 2.5 |
|---|---|---|
| SciCode | 34.4% | 38.5% |
| ALE-Bench | 566.05 | 301.65 |
| WeirdML | 40.9% | — |
| LMArena Coding | 1306 | — |

## Agentic & Tool Use

- gpt-oss-20b: 9.3 (#154)
- Mercury 2.5: —

| Benchmark | gpt-oss-20b | Mercury 2.5 |
|---|---|---|
| Terminal-Bench | 3.4% | — |

## Reasoning

- gpt-oss-20b: 19.3 (#261)
- Mercury 2.5: 22.4 (#193)

| Benchmark | gpt-oss-20b | Mercury 2.5 |
|---|---|---|
| CritPt | 1.4% | 0% |
| Kagi LLM Benchmark | 53.2% | — |
| Chess Puzzles | 4% | — |
| LMArena Hard Prompts | 1274 | — |
| DTBench | 68% | — |
| LMCA | 14.5% | — |
| Epoch Capabilities Index | 137.82 | — |

## Math

- gpt-oss-20b: 39.4 (#103)
- Mercury 2.5: 23.3 (#272)

| Benchmark | gpt-oss-20b | Mercury 2.5 |
|---|---|---|
| OTIS Mock AIME 2024-2025 | 65.3% | — |
| ProofBench | — | 3% |
| Omni-MATH | 56.5% | — |
| LMArena Math | 1317 | — |

## Knowledge

- gpt-oss-20b: 34.6 (#195)
- Mercury 2.5: —

| Benchmark | gpt-oss-20b | Mercury 2.5 |
|---|---|---|
| GPQA Diamond | 60.8% | — |
| MMLU-Pro | 74% | — |
| GPQA (HELM) | 59.4% | — |
| LMArena Expert | 1258 | — |

## Multilingual

- gpt-oss-20b: 42.2 (#197)
- Mercury 2.5: —

| Benchmark | gpt-oss-20b | Mercury 2.5 |
|---|---|---|
| LMArena Non-English | 1268 | — |
| LMArena Chinese | 1314 | — |
| LMArena German | 1255 | — |
| LMArena Japanese | 1244 | — |
| LMArena Korean | 1236 | — |
| LMArena Russian | 1278 | — |
| LMArena Spanish | 1267 | — |

## Instruction Following

- gpt-oss-20b: 61.8 (#240)
- Mercury 2.5: —

| Benchmark | gpt-oss-20b | Mercury 2.5 |
|---|---|---|
| IFEval | 73.2% | — |
| LMArena Instruction Following | 1236 | — |

## Long Context

- gpt-oss-20b: 37.9 (#209)
- Mercury 2.5: —

| Benchmark | gpt-oss-20b | Mercury 2.5 |
|---|---|---|
| LMArena Longer Query | 1250 | — |

## Writing & Preference

- gpt-oss-20b: 35.5 (#265)
- Mercury 2.5: —

| Benchmark | gpt-oss-20b | Mercury 2.5 |
|---|---|---|
| LMArena Text | 1287 | — |
| LMArena Creative Writing | 1201 | — |
| EQ-Bench Creative Writing | 666 | — |
| WildBench | 73.7% | — |
| LMArena Multi-Turn | 1268 | — |

## FAQ

### Is gpt-oss-20b better than Mercury 2.5?

gpt-oss-20b and Mercury 2.5 score almost the same on the Noometry Index (32.5 vs 33.5), so choose on price, context window or the category you care about most.

### Which is cheaper, gpt-oss-20b or Mercury 2.5?

gpt-oss-20b is cheaper. It lists at $0.018 per million input tokens and $0.09 per million output tokens; Mercury 2.5 lists at $0.04 and $0.15.

### Is gpt-oss-20b or Mercury 2.5 better for coding?

Mercury 2.5 scores higher on coding benchmarks: 39.5 versus 37.6 in the Noometry coding category.

### Which has the bigger context window?

Mercury 2.5 does, with 260K tokens against 131K.

### How many benchmarks do gpt-oss-20b and Mercury 2.5 share?

3 benchmarks have published results for both models. gpt-oss-20b has 34 scored results on Noometry and Mercury 2.5 has 4.