# GPT-5 Pro vs Step 3.5 Flash

> GPT-5 Pro is the stronger model overall, scoring 46.4 to 42.3 on the Noometry Index. Step 3.5 Flash costs 275× less per token, which makes it the better buy when GPT-5 Pro's lead doesn't matter for your workload.

- Canonical page: https://noometry.com/compare/gpt-5-pro-vs-step-3-5-flash
- Last updated: 2026-10-11
- Shared benchmarks: 0

## Summary

- The widest gap is in knowledge, where GPT-5 Pro leads 56.7 to 39.6.
- Step 3.5 Flash is cheaper at $0.10 / $0.30 per million input/output tokens, against $15 / $120 for GPT-5 Pro.
- GPT-5 Pro accepts more context: 400K tokens versus 256K.
- Step 3.5 Flash has downloadable open weights; the other is API-only.

## Snapshot

| | GPT-5 Pro | Step 3.5 Flash |
|---|---|---|
| Provider | OpenAI | StepFun |
| Noometry Index | 46.4 | 42.3 |
| Rank | 64 | 116 |
| Context | 400K | 256K |
| Input $/M | $15 | $0.10 |
| Output $/M | $120 | $0.30 |
| Weights | Proprietary | Open |

## Coding

- GPT-5 Pro: 44.0 (#80)
- Step 3.5 Flash: 42.4 (#105)

| Benchmark | GPT-5 Pro | Step 3.5 Flash |
|---|---|---|
| WeirdML | 60.4% | — |
| LMArena Coding | — | 1436 |
| AlgoTune | 1.31 | — |

## Reasoning

- GPT-5 Pro: 38.9 (#62)
- Step 3.5 Flash: 22.2 (#202)

| Benchmark | GPT-5 Pro | Step 3.5 Flash |
|---|---|---|
| ARC-AGI-2 | 18.3% | — |
| SimpleBench | 61.6% | — |
| Kagi LLM Benchmark | 76.8% | — |
| NYT Connections (extended) | — | 28.4% |
| ARC-AGI-1 | 70.2% | — |
| EnigmaEval | 18.8% | — |
| LMArena Hard Prompts | — | 1411 |
| Epoch Capabilities Index | 150.28 | — |

## Math

- GPT-5 Pro: 48.5 (#63)
- Step 3.5 Flash: 42.6 (#84)

| Benchmark | GPT-5 Pro | Step 3.5 Flash |
|---|---|---|
| FrontierMath (Tiers 1-3) | 55.8% | — |
| FrontierMath Tier 4 | 19.5% | — |
| MathArena Final-Answer Competitions | — | 66.8% |
| LMArena Math | — | 1408 |
| FrontierMath Tier 4 (v1) | 14.6% | — |

## Knowledge

- GPT-5 Pro: 56.7 (#42)
- Step 3.5 Flash: 39.6 (#132)

| Benchmark | GPT-5 Pro | Step 3.5 Flash |
|---|---|---|
| Humanity's Last Exam | 31.6% | — |
| LMArena Expert | — | 1421 |

## Multilingual

- GPT-5 Pro: —
- Step 3.5 Flash: 50.5 (#119)

| Benchmark | GPT-5 Pro | Step 3.5 Flash |
|---|---|---|
| LMArena Non-English | — | 1385 |
| LMArena Chinese | — | 1447 |
| LMArena French | — | 1421 |
| LMArena German | — | 1405 |
| LMArena Japanese | — | 1354 |
| LMArena Korean | — | 1352 |
| LMArena Russian | — | 1385 |
| LMArena Spanish | — | 1419 |

## Instruction Following

- GPT-5 Pro: —
- Step 3.5 Flash: 73.1 (#124)

| Benchmark | GPT-5 Pro | Step 3.5 Flash |
|---|---|---|
| LMArena Instruction Following | — | 1385 |

## Long Context

- GPT-5 Pro: —
- Step 3.5 Flash: 42.8 (#117)

| Benchmark | GPT-5 Pro | Step 3.5 Flash |
|---|---|---|
| LMArena Longer Query | — | 1402 |

## Writing & Preference

- GPT-5 Pro: —
- Step 3.5 Flash: 58.8 (#113)

| Benchmark | GPT-5 Pro | Step 3.5 Flash |
|---|---|---|
| LMArena Text | — | 1403 |
| LMArena Creative Writing | — | 1357 |
| LMArena Multi-Turn | — | 1405 |

## FAQ

### Is GPT-5 Pro better than Step 3.5 Flash?

GPT-5 Pro is the stronger model overall, scoring 46.4 to 42.3 on the Noometry Index. Step 3.5 Flash costs 275× less per token, which makes it the better buy when GPT-5 Pro's lead doesn't matter for your workload.

### Which is cheaper, GPT-5 Pro 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 Pro lists at $15 and $120.

### Is GPT-5 Pro or Step 3.5 Flash better for coding?

GPT-5 Pro scores higher on coding benchmarks: 44.0 versus 42.4 in the Noometry coding category.

### Which has the bigger context window?

GPT-5 Pro does, with 400K tokens against 256K.

### How many benchmarks do GPT-5 Pro and Step 3.5 Flash share?

0 benchmarks have published results for both models. GPT-5 Pro has 12 scored results on Noometry and Step 3.5 Flash has 19.