Model comparison
GPT-5.5 Pro vs Step 3.7 Flash
GPT-5.5 Pro is the stronger model overall, scoring 64.3 to 37.3 on the Noometry Index. Step 3.7 Flash costs 162× less per token, which makes it the better buy when GPT-5.5 Pro's lead doesn't matter for your workload.
Last verified . 1 shared benchmarks.
StepFunSummary
- They share 1 benchmark with published results for both. GPT-5.5 Pro scores higher in 2 categories and Step 3.7 Flash in 0 categories; 2 gaps are clear of the uncertainty.
- The widest gap is in reasoning, where GPT-5.5 Pro leads 73.3 to 21.6.
- The biggest single-benchmark swing is CritPt: 30.6% for GPT-5.5 Pro and 2.3% for Step 3.7 Flash.
- Step 3.7 Flash is cheaper at $0.18 / $1.11 per million input/output tokens, against $30 / $180 for GPT-5.5 Pro.
- GPT-5.5 Pro accepts more context: 1.05M tokens versus 256K.
- Step 3.7 Flash has downloadable open weights; the other is API-only.
Side by side
| GPT-5.5 Pro | Step 3.7 Flash | |
|---|---|---|
| Provider | OpenAI | StepFun |
| Noometry Index | 64.3 | 37.3 |
| Released | 2026-04-23 | 2026-05-29 |
| Weights | Proprietary | Open |
| Context window | 1.05M | 256K |
| Max output | 128K | 256K |
| Input $ / M tokens | $30 | $0.18 |
| Output $ / M tokens | $180 | $1.11 |
| Results tracked | 14 | 5 |
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Category by category
Coding Not comparable
GPT-5.5 Pro: —, Step 3.7 Flash: 40.0 (#150)
Reasoning GPT-5.5 Pro leads
GPT-5.5 Pro: 73.3 (#10), Step 3.7 Flash: 21.6 (#219)
| Benchmark | GPT-5.5 Pro | Step 3.7 Flash |
|---|---|---|
| CritPt | 30.6% | 2.3% |
| ARC-AGI-2 | 84.6% | — |
| SimpleBench | 76.9% | — |
| NYT Connections (extended) | — | 39.7% |
| ARC-AGI-1 | 96.5% | — |
| Chess Puzzles | 64% | — |
| DTBench | 96% | — |
| LMCA | 53.9% | — |
| Epoch Capabilities Index | 162.07 | — |
Math GPT-5.5 Pro leads
GPT-5.5 Pro: 84.0 (#10), Step 3.7 Flash: 42.9 (#82)
| Benchmark | GPT-5.5 Pro | Step 3.7 Flash |
|---|---|---|
| FrontierMath (Tiers 1-3) | 87.7% | — |
| FrontierMath Tier 4 | 78% | — |
| MathArena Final-Answer Competitions | — | 68.5% |
| OTIS Mock AIME 2024-2025 | 100% | — |
| FrontierMath (Feb 2025 set) | 52.4% | — |
| FrontierMath Tier 4 (v1) | 39.6% | — |
Knowledge Not comparable
GPT-5.5 Pro: 64.1 (#19), Step 3.7 Flash: —
| Benchmark | GPT-5.5 Pro | Step 3.7 Flash |
|---|---|---|
| GPQA Diamond | 93.9% | — |
Frequently asked questions
Is GPT-5.5 Pro better than Step 3.7 Flash?
GPT-5.5 Pro is the stronger model overall, scoring 64.3 to 37.3 on the Noometry Index. Step 3.7 Flash costs 162× less per token, which makes it the better buy when GPT-5.5 Pro's lead doesn't matter for your workload.
Which is cheaper, GPT-5.5 Pro or Step 3.7 Flash?
Step 3.7 Flash is cheaper. It lists at $0.18 per million input tokens and $1.11 per million output tokens; GPT-5.5 Pro lists at $30 and $180.
Which has the bigger context window?
GPT-5.5 Pro does, with 1.05M tokens against 256K.
How many benchmarks do GPT-5.5 Pro and Step 3.7 Flash share?
1 benchmark has published results for both models. GPT-5.5 Pro has 14 scored results on Noometry and Step 3.7 Flash has 5.