# GPT-5.3 Chat vs Step 3.5 Flash

> GPT-5.3 Chat and Step 3.5 Flash score almost the same on the Noometry Index (42.1 vs 41.7), so choose on price, context window or the category you care about most.

- Canonical page: https://noometry.com/compare/gpt-5-3-chat-vs-step-3-5-flash
- Last updated: 2026-10-10
- Shared benchmarks: 17

## Summary

- They share 17 benchmarks with published results for both. GPT-5.3 Chat scores higher in 2 categories and Step 3.5 Flash in 6 categories; 3 gaps are clear of the uncertainty.
- The widest gap is in reasoning, where GPT-5.3 Chat leads 27.3 to 21.2.
- Step 3.5 Flash is cheaper at $0.10 / $0.30 per million input/output tokens, against $1.75 / $14 for GPT-5.3 Chat.
- Step 3.5 Flash accepts more context: 256K tokens versus 128K.
- Step 3.5 Flash has downloadable open weights; the other is API-only.

## Snapshot

| | GPT-5.3 Chat | Step 3.5 Flash |
|---|---|---|
| Provider | OpenAI | StepFun |
| Noometry Index | 42.1 | 41.7 |
| Rank | 109 | 116 |
| Context | 128K | 256K |
| Input $/M | $1.75 | $0.10 |
| Output $/M | $14 | $0.30 |
| Weights | Proprietary | Open |

## Coding

- GPT-5.3 Chat: 40.8 (#124)
- Step 3.5 Flash: 41.7 (#106)

| Benchmark | GPT-5.3 Chat | Step 3.5 Flash |
|---|---|---|
| LMArena Coding | 1408 | 1436 |

## Reasoning

- GPT-5.3 Chat: 27.3 (#105)
- Step 3.5 Flash: 21.2 (#202)

| Benchmark | GPT-5.3 Chat | Step 3.5 Flash |
|---|---|---|
| LMArena Hard Prompts | 1399 | 1411 |
| NYT Connections (extended) | — | 28.4% |

## Math

- GPT-5.3 Chat: 35.4 (#146)
- Step 3.5 Flash: 40.6 (#77)

| Benchmark | GPT-5.3 Chat | Step 3.5 Flash |
|---|---|---|
| LMArena Math | 1389 | 1408 |
| MathArena Final-Answer Competitions | — | 66.8% |

## Knowledge

- GPT-5.3 Chat: 38.2 (#137)
- Step 3.5 Flash: 39.0 (#127)

| Benchmark | GPT-5.3 Chat | Step 3.5 Flash |
|---|---|---|
| LMArena Expert | 1397 | 1422 |

## Multilingual

- GPT-5.3 Chat: 50.5 (#119)
- Step 3.5 Flash: 50.7 (#115)

| Benchmark | GPT-5.3 Chat | Step 3.5 Flash |
|---|---|---|
| LMArena Non-English | 1383 | 1386 |
| LMArena Chinese | 1433 | 1448 |
| LMArena French | 1398 | 1421 |
| LMArena German | 1384 | 1404 |
| LMArena Japanese | 1351 | 1353 |
| LMArena Korean | 1347 | 1350 |
| LMArena Russian | 1400 | 1385 |
| LMArena Spanish | 1371 | 1419 |

## Instruction Following

- GPT-5.3 Chat: 73.0 (#124)
- Step 3.5 Flash: 73.3 (#119)

| Benchmark | GPT-5.3 Chat | Step 3.5 Flash |
|---|---|---|
| LMArena Instruction Following | 1378 | 1385 |

## Long Context

- GPT-5.3 Chat: 42.6 (#115)
- Step 3.5 Flash: 42.8 (#112)

| Benchmark | GPT-5.3 Chat | Step 3.5 Flash |
|---|---|---|
| LMArena Longer Query | 1396 | 1402 |

## Writing & Preference

- GPT-5.3 Chat: 63.3 (#65)
- Step 3.5 Flash: 59.0 (#108)

| Benchmark | GPT-5.3 Chat | Step 3.5 Flash |
|---|---|---|
| LMArena Text | 1389 | 1403 |
| LMArena Creative Writing | 1356 | 1357 |
| LMArena Multi-Turn | 1413 | 1405 |
| EQ-Bench Creative Writing | 1690 | — |

## FAQ

### Is GPT-5.3 Chat better than Step 3.5 Flash?

GPT-5.3 Chat and Step 3.5 Flash score almost the same on the Noometry Index (42.1 vs 41.7), so choose on price, context window or the category you care about most.

### Which is cheaper, GPT-5.3 Chat or Step 3.5 Flash?

Step 3.5 Flash is cheaper. It lists at $0.10 per million input tokens and $0.30 per million output tokens; GPT-5.3 Chat lists at $1.75 and $14.

### Is GPT-5.3 Chat or Step 3.5 Flash better for coding?

They score almost the same on coding (40.8 vs 41.7); test both on your own repository before choosing.

### Which has the bigger context window?

Step 3.5 Flash does, with 256K tokens against 128K.

### How many benchmarks do GPT-5.3 Chat and Step 3.5 Flash share?

17 benchmarks have published results for both models. GPT-5.3 Chat has 18 scored results on Noometry and Step 3.5 Flash has 19.