Model comparison
GPT-5.3 Chat vs Mercury 2
GPT-5.3 Chat is the stronger model overall, scoring 42.8 to 39.1 on the Noometry Index. Mercury 2 costs 13× less per token, which makes it the better buy when GPT-5.3 Chat's lead doesn't matter for your workload.
Last verified . 11 shared benchmarks.
Summary
- They share 11 benchmarks with published results for both. GPT-5.3 Chat scores higher in 7 categories and Mercury 2 in 0 categories; 7 gaps are clear of the uncertainty.
- The widest gap is in writing & preference, where GPT-5.3 Chat leads 63.1 to 53.8.
- Mercury 2 is cheaper at $0.25 / $0.75 per million input/output tokens, against $1.75 / $14 for GPT-5.3 Chat.
Side by side
| GPT-5.3 Chat | Mercury 2 | |
|---|---|---|
| Provider | OpenAI | Inception |
| Noometry Index | 42.8 | 39.1 |
| Released | 2026-03-03 | 2026-02-20 |
| Weights | Proprietary | Proprietary |
| Context window | 128K | 128K |
| Max output | 16K | 50K |
| Input $ / M tokens | $1.75 | $0.25 |
| Output $ / M tokens | $14 | $0.75 |
| Results tracked | 18 | 17 |
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Category by category
Coding GPT-5.3 Chat leads
GPT-5.3 Chat: 41.4 (#124), Mercury 2: 33.5 (#255)
| Benchmark | GPT-5.3 Chat | Mercury 2 |
|---|---|---|
| LMArena Coding | 1408 | 1391 |
| LMArena WebDev | — | 1171 |
| SciCode | — | 38.7% |
| WeirdML | — | 43.2% |
| ALE-Bench | — | 785.58 |
Reasoning GPT-5.3 Chat leads
GPT-5.3 Chat: 28.5 (#102), Mercury 2: 23.8 (#170)
| Benchmark | GPT-5.3 Chat | Mercury 2 |
|---|---|---|
| LMArena Hard Prompts | 1399 | 1362 |
| CritPt | — | 0.8% |
Math Not comparable
GPT-5.3 Chat: 38.2 (#142), Mercury 2: —
| Benchmark | GPT-5.3 Chat | Mercury 2 |
|---|---|---|
| LMArena Math | 1389 | — |
Knowledge GPT-5.3 Chat leads
GPT-5.3 Chat: 38.8 (#140), Mercury 2: 36.2 (#172)
| Benchmark | GPT-5.3 Chat | Mercury 2 |
|---|---|---|
| LMArena Expert | 1397 | 1358 |
| Vectara Hallucination Rate | — | 12.3% |
Multilingual GPT-5.3 Chat leads
GPT-5.3 Chat: 50.3 (#124), Mercury 2: 46.6 (#157)
| Benchmark | GPT-5.3 Chat | Mercury 2 |
|---|---|---|
| LMArena Non-English | 1382 | 1331 |
| LMArena Chinese | 1432 | 1417 |
| LMArena Russian | 1400 | 1304 |
| LMArena French | 1397 | — |
| LMArena German | 1384 | — |
| LMArena Japanese | 1352 | — |
| LMArena Korean | 1346 | — |
| LMArena Spanish | 1371 | — |
Instruction Following GPT-5.3 Chat leads
GPT-5.3 Chat: 72.8 (#129), Mercury 2: 70.2 (#165)
| Benchmark | GPT-5.3 Chat | Mercury 2 |
|---|---|---|
| LMArena Instruction Following | 1378 | 1329 |
Long Context GPT-5.3 Chat leads
GPT-5.3 Chat: 42.6 (#120), Mercury 2: 40.5 (#154)
| Benchmark | GPT-5.3 Chat | Mercury 2 |
|---|---|---|
| LMArena Longer Query | 1396 | 1330 |
Writing & Preference GPT-5.3 Chat leads
GPT-5.3 Chat: 63.1 (#68), Mercury 2: 53.8 (#155)
| Benchmark | GPT-5.3 Chat | Mercury 2 |
|---|---|---|
| LMArena Text | 1389 | 1355 |
| LMArena Creative Writing | 1355 | 1289 |
| LMArena Multi-Turn | 1412 | 1358 |
| EQ-Bench Creative Writing | 1690 | — |
Frequently asked questions
Is GPT-5.3 Chat better than Mercury 2?
GPT-5.3 Chat is the stronger model overall, scoring 42.8 to 39.1 on the Noometry Index. Mercury 2 costs 13× less per token, which makes it the better buy when GPT-5.3 Chat's lead doesn't matter for your workload.
Which is cheaper, GPT-5.3 Chat or Mercury 2?
Mercury 2 is cheaper. It lists at $0.25 per million input tokens and $0.75 per million output tokens; GPT-5.3 Chat lists at $1.75 and $14.
Is GPT-5.3 Chat or Mercury 2 better for coding?
GPT-5.3 Chat scores higher on coding benchmarks: 41.4 versus 33.5 in the Noometry coding category.
Which has the bigger context window?
Both accept 128K tokens.
How many benchmarks do GPT-5.3 Chat and Mercury 2 share?
11 benchmarks have published results for both models. GPT-5.3 Chat has 18 scored results on Noometry and Mercury 2 has 17.