Model comparison
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.
Last verified . 0 shared benchmarks.
StepFunSummary
- 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.
Side by side
| GPT-5 Pro | Step 3.5 Flash | |
|---|---|---|
| Provider | OpenAI | StepFun |
| Noometry Index | 46.4 | 42.3 |
| Released | 2025-10-06 | 2026-01-29 |
| Weights | Proprietary | Open |
| Context window | 400K | 256K |
| Max output | 272K | 256K |
| Input $ / M tokens | $15 | $0.10 |
| Output $ / M tokens | $120 | $0.30 |
| Results tracked | 12 | 19 |
Sponsored placements are available on pages like this one. Advertise on Noometry
Category by category
Coding GPT-5 Pro leads
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 leads
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 leads
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 leads
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 Not comparable
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 Not comparable
GPT-5 Pro: —, Step 3.5 Flash: 73.1 (#124)
| Benchmark | GPT-5 Pro | Step 3.5 Flash |
|---|---|---|
| LMArena Instruction Following | — | 1385 |
Long Context Not comparable
GPT-5 Pro: —, Step 3.5 Flash: 42.8 (#117)
| Benchmark | GPT-5 Pro | Step 3.5 Flash |
|---|---|---|
| LMArena Longer Query | — | 1402 |
Writing & Preference Not comparable
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 |
Frequently asked questions
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.