Model comparison
GPT-5.5 Instant vs Mercury 2
GPT-5.5 Instant is the stronger model overall, scoring 42.7 to 39.1 on the Noometry Index.
Last verified . 13 shared benchmarks.
Summary
- They share 13 benchmarks with published results for both. GPT-5.5 Instant scores higher in 7 categories and Mercury 2 in 0 categories; 7 gaps are clear of the uncertainty.
- The widest gap is in knowledge, where GPT-5.5 Instant leads 48.9 to 36.2.
- The biggest single-benchmark swing is SciCode: 48.6% for GPT-5.5 Instant and 38.7% for Mercury 2.
Side by side
| GPT-5.5 Instant | Mercury 2 | |
|---|---|---|
| Provider | OpenAI | Inception |
| Noometry Index | 42.7 | 39.1 |
| Released | 2026-05-05 | 2026-02-20 |
| Weights | Proprietary | Proprietary |
| Context window | — | 128K |
| Max output | — | 50K |
| Input $ / M tokens | — | $0.25 |
| Output $ / M tokens | — | $0.75 |
| Results tracked | 27 | 17 |
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Category by category
Coding GPT-5.5 Instant leads
GPT-5.5 Instant: 44.3 (#74), Mercury 2: 33.5 (#255)
| Benchmark | GPT-5.5 Instant | Mercury 2 |
|---|---|---|
| SciCode | 48.6% | 38.7% |
| LMArena Coding | 1433 | 1391 |
| LMArena WebDev | — | 1171 |
| WeirdML | — | 43.2% |
| ALE-Bench | — | 785.58 |
Reasoning GPT-5.5 Instant leads
GPT-5.5 Instant: 24.9 (#155), Mercury 2: 23.8 (#170)
| Benchmark | GPT-5.5 Instant | Mercury 2 |
|---|---|---|
| CritPt | 0% | 0.8% |
| LMArena Hard Prompts | 1426 | 1362 |
| Chess Puzzles | 12% | — |
| Epoch Capabilities Index | 142.52 | — |
Math Not comparable
GPT-5.5 Instant: 26.5 (#259), Mercury 2: —
| Benchmark | GPT-5.5 Instant | Mercury 2 |
|---|---|---|
| FrontierMath (Tiers 1-3) | 26.3% | — |
| FrontierMath Tier 4 | 2.4% | — |
| OTIS Mock AIME 2024-2025 | 68.1% | — |
| LMArena Math | 1420 | — |
Knowledge GPT-5.5 Instant leads
GPT-5.5 Instant: 48.9 (#74), Mercury 2: 36.2 (#172)
| Benchmark | GPT-5.5 Instant | Mercury 2 |
|---|---|---|
| LMArena Expert | 1409 | 1358 |
| GPQA Diamond | 82.5% | — |
| Vectara Hallucination Rate | — | 12.3% |
Multimodal Not comparable
GPT-5.5 Instant: 40.0 (#52), Mercury 2: —
| Benchmark | GPT-5.5 Instant | Mercury 2 |
|---|---|---|
| LMArena Vision | 1250 | — |
| LMArena Document | 1403 | — |
Multilingual GPT-5.5 Instant leads
GPT-5.5 Instant: 52.8 (#80), Mercury 2: 46.6 (#157)
| Benchmark | GPT-5.5 Instant | Mercury 2 |
|---|---|---|
| LMArena Non-English | 1417 | 1331 |
| LMArena Chinese | 1456 | 1417 |
| LMArena Russian | 1431 | 1304 |
| LMArena French | 1428 | — |
| LMArena German | 1411 | — |
| LMArena Japanese | 1408 | — |
| LMArena Korean | 1392 | — |
| LMArena Spanish | 1429 | — |
Instruction Following GPT-5.5 Instant leads
GPT-5.5 Instant: 74.2 (#100), Mercury 2: 70.2 (#165)
| Benchmark | GPT-5.5 Instant | Mercury 2 |
|---|---|---|
| LMArena Instruction Following | 1406 | 1329 |
Long Context GPT-5.5 Instant leads
GPT-5.5 Instant: 43.4 (#96), Mercury 2: 40.5 (#154)
| Benchmark | GPT-5.5 Instant | Mercury 2 |
|---|---|---|
| LMArena Longer Query | 1422 | 1330 |
Writing & Preference GPT-5.5 Instant leads
GPT-5.5 Instant: 61.8 (#85), Mercury 2: 53.8 (#155)
| Benchmark | GPT-5.5 Instant | Mercury 2 |
|---|---|---|
| LMArena Text | 1419 | 1355 |
| LMArena Creative Writing | 1419 | 1289 |
| LMArena Multi-Turn | 1433 | 1358 |
Frequently asked questions
Is GPT-5.5 Instant better than Mercury 2?
GPT-5.5 Instant is the stronger model overall, scoring 42.7 to 39.1 on the Noometry Index.
Is GPT-5.5 Instant or Mercury 2 better for coding?
GPT-5.5 Instant scores higher on coding benchmarks: 44.3 versus 33.5 in the Noometry coding category.
How many benchmarks do GPT-5.5 Instant and Mercury 2 share?
13 benchmarks have published results for both models. GPT-5.5 Instant has 27 scored results on Noometry and Mercury 2 has 17.