Model comparison
gpt-oss-20b vs Mercury 2.5
gpt-oss-20b has enough public results to be ranked (#249); Mercury 2.5 does not yet, so treat this comparison as directional.
Last verified . 1 shared benchmarks.
Summary
- They share 1 benchmark with published results for both. gpt-oss-20b scores higher in 1 category and Mercury 2.5 in 0 categories; one gap is clear of the uncertainty.
- The widest gap is in math, where gpt-oss-20b leads 37.6 to 22.4.
- 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.
Side by side
| gpt-oss-20b | Mercury 2.5 | |
|---|---|---|
| Provider | OpenAI | Inception |
| Noometry Index | 32.1 | 30.2 |
| Released | 2025-08-05 | 2026-09-08 |
| Weights | Open | Proprietary |
| Context window | 131K | 260K |
| Max output | 16K | 66K |
| Input $ / M tokens | $0.018 | $0.04 |
| Output $ / M tokens | $0.09 | $0.15 |
| Results tracked | 34 | 2 |
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Category by category
Coding Not comparable
gpt-oss-20b: 37.1 (#185), Mercury 2.5: —
| Benchmark | gpt-oss-20b | Mercury 2.5 |
|---|---|---|
| ALE-Bench | 566.05 | 301.65 |
| SciCode | 34.4% | — |
| WeirdML | 40.9% | — |
| LMArena Coding | 1307 | — |
Agentic & Tool Use Not comparable
gpt-oss-20b: 9.2 (#146), Mercury 2.5: —
| Benchmark | gpt-oss-20b | Mercury 2.5 |
|---|---|---|
| Terminal-Bench | 3.4% | — |
Reasoning Not comparable
gpt-oss-20b: 18.8 (#251), Mercury 2.5: —
| Benchmark | gpt-oss-20b | Mercury 2.5 |
|---|---|---|
| Kagi LLM Benchmark | 53.2% | — |
| CritPt | 1.4% | — |
| Chess Puzzles | 4% | — |
| LMArena Hard Prompts | 1274 | — |
| DTBench | 68% | — |
| LMCA | 14.5% | — |
| Epoch Capabilities Index | 137.81 | — |
Math gpt-oss-20b leads
gpt-oss-20b: 37.6 (#93), Mercury 2.5: 22.4
| Benchmark | gpt-oss-20b | Mercury 2.5 |
|---|---|---|
| OTIS Mock AIME 2024-2025 | 65.3% | — |
| ProofBench | — | 3% |
| Omni-MATH | 56.5% | — |
| LMArena Math | 1317 | — |
Knowledge Not comparable
gpt-oss-20b: 34.6 (#186), 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 Not comparable
gpt-oss-20b: 42.4 (#192), Mercury 2.5: —
| Benchmark | gpt-oss-20b | Mercury 2.5 |
|---|---|---|
| LMArena Non-English | 1269 | — |
| LMArena Chinese | 1311 | — |
| LMArena German | 1249 | — |
| LMArena Japanese | 1245 | — |
| LMArena Korean | 1239 | — |
| LMArena Russian | 1279 | — |
| LMArena Spanish | 1267 | — |
Instruction Following Not comparable
gpt-oss-20b: 62.0 (#235), Mercury 2.5: —
| Benchmark | gpt-oss-20b | Mercury 2.5 |
|---|---|---|
| IFEval | 73.2% | — |
| LMArena Instruction Following | 1236 | — |
Long Context Not comparable
gpt-oss-20b: 37.9 (#203), Mercury 2.5: —
| Benchmark | gpt-oss-20b | Mercury 2.5 |
|---|---|---|
| LMArena Longer Query | 1251 | — |
Writing & Preference Not comparable
gpt-oss-20b: 35.8 (#260), Mercury 2.5: —
| Benchmark | gpt-oss-20b | Mercury 2.5 |
|---|---|---|
| LMArena Text | 1288 | — |
| LMArena Creative Writing | 1201 | — |
| EQ-Bench Creative Writing | 666 | — |
| WildBench | 73.7% | — |
| LMArena Multi-Turn | 1268 | — |
Frequently asked questions
Is gpt-oss-20b better than Mercury 2.5?
gpt-oss-20b has enough public results to be ranked (#249); Mercury 2.5 does not yet, so treat this comparison as directional.
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.
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?
1 benchmark has published results for both models. gpt-oss-20b has 34 scored results on Noometry and Mercury 2.5 has 2.