# GPT-5.5 Instant vs Step 3.5 Flash

> GPT-5.5 Instant and Step 3.5 Flash score almost the same on the Noometry Index (42.5 vs 41.7), so choose on price, context window or the category you care about most.

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

## Summary

- They share 17 benchmarks with published results for both. GPT-5.5 Instant scores higher in 7 categories and Step 3.5 Flash in 1 category; 7 gaps are clear of the uncertainty.
- The widest gap is in math, where Step 3.5 Flash leads 40.6 to 26.1.
- Step 3.5 Flash has downloadable open weights; the other is API-only.

## Snapshot

| | GPT-5.5 Instant | Step 3.5 Flash |
|---|---|---|
| Provider | OpenAI | StepFun |
| Noometry Index | 42.5 | 41.7 |
| Rank | 99 | 116 |
| Context | — | 256K |
| Input $/M | — | $0.10 |
| Output $/M | — | $0.30 |
| Weights | Proprietary | Open |

## Coding

- GPT-5.5 Instant: 43.7 (#73)
- Step 3.5 Flash: 41.7 (#106)

| Benchmark | GPT-5.5 Instant | Step 3.5 Flash |
|---|---|---|
| LMArena Coding | 1433 | 1436 |
| SciCode | 48.6% | — |

## Reasoning

- GPT-5.5 Instant: 24.2 (#149)
- Step 3.5 Flash: 21.2 (#202)

| Benchmark | GPT-5.5 Instant | Step 3.5 Flash |
|---|---|---|
| LMArena Hard Prompts | 1426 | 1411 |
| NYT Connections (extended) | — | 28.4% |
| CritPt | 0% | — |
| Chess Puzzles | 12% | — |
| Epoch Capabilities Index | 142.48 | — |

## Math

- GPT-5.5 Instant: 26.1 (#241)
- Step 3.5 Flash: 40.6 (#77)

| Benchmark | GPT-5.5 Instant | Step 3.5 Flash |
|---|---|---|
| LMArena Math | 1420 | 1408 |
| FrontierMath (Tiers 1-3) | 26.3% | — |
| FrontierMath Tier 4 | 2.4% | — |
| MathArena Final-Answer Competitions | — | 66.8% |
| OTIS Mock AIME 2024-2025 | 68.1% | — |

## Knowledge

- GPT-5.5 Instant: 48.9 (#68)
- Step 3.5 Flash: 39.0 (#127)

| Benchmark | GPT-5.5 Instant | Step 3.5 Flash |
|---|---|---|
| LMArena Expert | 1409 | 1422 |
| GPQA Diamond | 82.5% | — |

## Multimodal

- GPT-5.5 Instant: 39.3 (#48)
- Step 3.5 Flash: —

| Benchmark | GPT-5.5 Instant | Step 3.5 Flash |
|---|---|---|
| LMArena Vision | 1250 | — |
| LMArena Document | 1403 | — |

## Multilingual

- GPT-5.5 Instant: 53.0 (#76)
- Step 3.5 Flash: 50.7 (#115)

| Benchmark | GPT-5.5 Instant | Step 3.5 Flash |
|---|---|---|
| LMArena Non-English | 1417 | 1386 |
| LMArena Chinese | 1457 | 1448 |
| LMArena French | 1428 | 1421 |
| LMArena German | 1410 | 1404 |
| LMArena Japanese | 1408 | 1353 |
| LMArena Korean | 1393 | 1350 |
| LMArena Russian | 1430 | 1385 |
| LMArena Spanish | 1430 | 1419 |

## Instruction Following

- GPT-5.5 Instant: 74.4 (#94)
- Step 3.5 Flash: 73.3 (#119)

| Benchmark | GPT-5.5 Instant | Step 3.5 Flash |
|---|---|---|
| LMArena Instruction Following | 1407 | 1385 |

## Long Context

- GPT-5.5 Instant: 43.4 (#92)
- Step 3.5 Flash: 42.8 (#112)

| Benchmark | GPT-5.5 Instant | Step 3.5 Flash |
|---|---|---|
| LMArena Longer Query | 1422 | 1402 |

## Writing & Preference

- GPT-5.5 Instant: 62.0 (#81)
- Step 3.5 Flash: 59.0 (#108)

| Benchmark | GPT-5.5 Instant | Step 3.5 Flash |
|---|---|---|
| LMArena Text | 1419 | 1403 |
| LMArena Creative Writing | 1420 | 1357 |
| LMArena Multi-Turn | 1434 | 1405 |

## FAQ

### Is GPT-5.5 Instant better than Step 3.5 Flash?

GPT-5.5 Instant and Step 3.5 Flash score almost the same on the Noometry Index (42.5 vs 41.7), so choose on price, context window or the category you care about most.

### Is GPT-5.5 Instant or Step 3.5 Flash better for coding?

GPT-5.5 Instant scores higher on coding benchmarks: 43.7 versus 41.7 in the Noometry coding category.

### How many benchmarks do GPT-5.5 Instant and Step 3.5 Flash share?

17 benchmarks have published results for both models. GPT-5.5 Instant has 27 scored results on Noometry and Step 3.5 Flash has 19.