# GPT-5.3 Chat vs gpt-oss-120b

> GPT-5.3 Chat is the stronger model overall, scoring 42.8 to 36.3 on the Noometry Index. gpt-oss-120b costs 69× less per token, which makes it the better buy when GPT-5.3 Chat's lead doesn't matter for your workload.

- Canonical page: https://noometry.com/compare/gpt-5-3-chat-vs-gpt-oss-120b
- Last updated: 2026-10-10
- Shared benchmarks: 18

## Summary

- They share 18 benchmarks with published results for both. GPT-5.3 Chat scores higher in 6 categories and gpt-oss-120b in 2 categories; 8 gaps are clear of the uncertainty.
- The widest gap is in writing & preference, where GPT-5.3 Chat leads 63.1 to 46.5.
- gpt-oss-120b is cheaper at $0.037 / $0.17 per million input/output tokens, against $1.75 / $14 for GPT-5.3 Chat.
- gpt-oss-120b accepts more context: 131K tokens versus 128K.
- gpt-oss-120b has downloadable open weights; the other is API-only.

## Snapshot

| | GPT-5.3 Chat | gpt-oss-120b |
|---|---|---|
| Provider | OpenAI | OpenAI |
| Noometry Index | 42.8 | 36.3 |
| Rank | 109 | 217 |
| Context | 128K | 131K |
| Input $/M | $1.75 | $0.037 |
| Output $/M | $14 | $0.17 |
| Weights | Proprietary | Open |

## Coding

- GPT-5.3 Chat: 41.4 (#124)
- gpt-oss-120b: 33.5 (#256)

| Benchmark | GPT-5.3 Chat | gpt-oss-120b |
|---|---|---|
| LMArena Coding | 1408 | 1380 |
| SWE-bench Verified (bash only) | — | 26% |
| Aider Polyglot | — | 41.8% |
| SciCode | — | 36% |
| WeirdML | — | 48.2% |
| ALE-Bench | — | 575.62 |
| AlgoTune | — | 1.41 |

## Agentic & Tool Use

- GPT-5.3 Chat: —
- gpt-oss-120b: 12.2 (#153)

| Benchmark | GPT-5.3 Chat | gpt-oss-120b |
|---|---|---|
| Terminal-Bench | — | 18.7% |
| APEX-Agents | — | 4.4% |
| METR Time Horizons | — | 56.6% |
| Vending-Bench 2 | — | -21.53 |

## Reasoning

- GPT-5.3 Chat: 28.5 (#102)
- gpt-oss-120b: 20.0 (#245)

| Benchmark | GPT-5.3 Chat | gpt-oss-120b |
|---|---|---|
| LMArena Hard Prompts | 1399 | 1364 |
| SimpleBench | — | 22.1% |
| Kagi LLM Benchmark | — | 58.6% |
| CritPt | — | 1.1% |
| Chess Puzzles | — | 20% |
| Mystery Game Puzzles | — | 2% |
| DTBench | — | 76.3% |
| LMCA | — | 22.1% |
| Surface Evolver Bench | — | 25% |
| Epoch Capabilities Index | — | 139.93 |

## Math

- GPT-5.3 Chat: 38.2 (#142)
- gpt-oss-120b: 52.5 (#50)

| Benchmark | GPT-5.3 Chat | gpt-oss-120b |
|---|---|---|
| LMArena Math | 1389 | 1389 |
| OTIS Mock AIME 2024-2025 | — | 88.9% |
| Omni-MATH | — | 68.8% |

## Knowledge

- GPT-5.3 Chat: 38.8 (#140)
- gpt-oss-120b: 42.4 (#96)

| Benchmark | GPT-5.3 Chat | gpt-oss-120b |
|---|---|---|
| LMArena Expert | 1397 | 1356 |
| GPQA Diamond | — | 75.8% |
| MMLU-Pro | — | 79.5% |
| Confabulations | — | 15.7% |
| Vectara Hallucination Rate | — | 14.2% |
| GPQA (HELM) | — | 68.4% |

## Multilingual

- GPT-5.3 Chat: 50.3 (#124)
- gpt-oss-120b: 48.0 (#147)

| Benchmark | GPT-5.3 Chat | gpt-oss-120b |
|---|---|---|
| LMArena Non-English | 1382 | 1351 |
| LMArena Chinese | 1432 | 1385 |
| LMArena French | 1397 | 1369 |
| LMArena German | 1384 | 1353 |
| LMArena Japanese | 1352 | 1331 |
| LMArena Korean | 1346 | 1282 |
| LMArena Russian | 1400 | 1343 |
| LMArena Spanish | 1371 | 1389 |

## Instruction Following

- GPT-5.3 Chat: 72.8 (#129)
- gpt-oss-120b: 69.3 (#173)

| Benchmark | GPT-5.3 Chat | gpt-oss-120b |
|---|---|---|
| LMArena Instruction Following | 1378 | 1318 |
| IFEval | — | 83.6% |

## Long Context

- GPT-5.3 Chat: 42.6 (#120)
- gpt-oss-120b: 31.4 (#278)

| Benchmark | GPT-5.3 Chat | gpt-oss-120b |
|---|---|---|
| LMArena Longer Query | 1396 | 1319 |
| Fiction.LiveBench | — | 44.4% |

## Writing & Preference

- GPT-5.3 Chat: 63.1 (#68)
- gpt-oss-120b: 46.5 (#217)

| Benchmark | GPT-5.3 Chat | gpt-oss-120b |
|---|---|---|
| LMArena Text | 1389 | 1365 |
| LMArena Creative Writing | 1355 | 1275 |
| EQ-Bench Creative Writing | 1690 | 961 |
| LMArena Multi-Turn | 1412 | 1340 |
| Short-Story Creative Writing | — | 77.1% |
| WildBench | — | 84.5% |

## FAQ

### Is GPT-5.3 Chat better than gpt-oss-120b?

GPT-5.3 Chat is the stronger model overall, scoring 42.8 to 36.3 on the Noometry Index. gpt-oss-120b costs 69× 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 gpt-oss-120b?

gpt-oss-120b is cheaper. It lists at $0.037 per million input tokens and $0.17 per million output tokens; GPT-5.3 Chat lists at $1.75 and $14.

### Is GPT-5.3 Chat or gpt-oss-120b 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?

gpt-oss-120b does, with 131K tokens against 128K.

### How many benchmarks do GPT-5.3 Chat and gpt-oss-120b share?

18 benchmarks have published results for both models. GPT-5.3 Chat has 18 scored results on Noometry and gpt-oss-120b has 48.