# Claude Sonnet 5.5 vs Step 3.5 Flash

> Claude Sonnet 5.5 is the stronger model overall, scoring 60.5 to 41.7 on the Noometry Index. Step 3.5 Flash costs 27× less per token, which makes it the better buy when Claude Sonnet 5.5's lead doesn't matter for your workload.

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

## Summary

- The widest gap is in math, where Claude Sonnet 5.5 leads 88.7 to 40.6.
- Step 3.5 Flash is cheaper at $0.10 / $0.30 per million input/output tokens, against $2 / $10 for Claude Sonnet 5.5.
- Claude Sonnet 5.5 accepts more context: 1M tokens versus 256K.
- Step 3.5 Flash has downloadable open weights; the other is API-only.

## Snapshot

| | Claude Sonnet 5.5 | Step 3.5 Flash |
|---|---|---|
| Provider | Anthropic | StepFun |
| Noometry Index | 60.5 | 41.7 |
| Rank | 10 | 116 |
| Context | 1M | 256K |
| Input $/M | $2 | $0.10 |
| Output $/M | $10 | $0.30 |
| Weights | Proprietary | Open |

## Coding

- Claude Sonnet 5.5: 65.5 (#6)
- Step 3.5 Flash: 41.7 (#106)

| Benchmark | Claude Sonnet 5.5 | Step 3.5 Flash |
|---|---|---|
| FrontierCode | 52.1% | — |
| CursorBench | 55.5% | — |
| LMArena WebDev | 1699 | — |
| FrontierSWE | 61.9% | — |
| SciCode | 61% | — |
| LMArena Coding | — | 1436 |
| ALE-Bench | 1,819 | — |

## Agentic & Tool Use

- Claude Sonnet 5.5: 44.9 (#14)
- Step 3.5 Flash: —

| Benchmark | Claude Sonnet 5.5 | Step 3.5 Flash |
|---|---|---|
| APEX-Agents | 75.5% | — |

## Reasoning

- Claude Sonnet 5.5: 52.4 (#29)
- Step 3.5 Flash: 21.2 (#202)

| Benchmark | Claude Sonnet 5.5 | Step 3.5 Flash |
|---|---|---|
| NYT Connections (extended) | — | 28.4% |
| CritPt | 31.4% | — |
| LMArena Hard Prompts | — | 1411 |
| Mystery Game Puzzles | 65% | — |

## Math

- Claude Sonnet 5.5: 88.7 (#4)
- Step 3.5 Flash: 40.6 (#77)

| Benchmark | Claude Sonnet 5.5 | Step 3.5 Flash |
|---|---|---|
| FrontierMath (Tiers 1-3) | 88.8% | — |
| FrontierMath Tier 4 | 80.5% | — |
| MathArena Final-Answer Competitions | — | 66.8% |
| OTIS Mock AIME 2024-2025 | 100% | — |
| ProofBench | 100% | — |
| LMArena Math | — | 1408 |

## Knowledge

- Claude Sonnet 5.5: 66.0 (#11)
- Step 3.5 Flash: 39.0 (#127)

| Benchmark | Claude Sonnet 5.5 | Step 3.5 Flash |
|---|---|---|
| GPQA Diamond | 95.6% | — |
| SimpleQA Verified | 46.5% | — |
| LMArena Expert | — | 1422 |

## Multimodal

- Claude Sonnet 5.5: 53.2 (#5)
- Step 3.5 Flash: —

| Benchmark | Claude Sonnet 5.5 | Step 3.5 Flash |
|---|---|---|
| Furniture Assembly | 75% | — |

## Multilingual

- Claude Sonnet 5.5: —
- Step 3.5 Flash: 50.7 (#115)

| Benchmark | Claude Sonnet 5.5 | Step 3.5 Flash |
|---|---|---|
| LMArena Non-English | — | 1386 |
| LMArena Chinese | — | 1448 |
| LMArena French | — | 1421 |
| LMArena German | — | 1404 |
| LMArena Japanese | — | 1353 |
| LMArena Korean | — | 1350 |
| LMArena Russian | — | 1385 |
| LMArena Spanish | — | 1419 |

## Instruction Following

- Claude Sonnet 5.5: —
- Step 3.5 Flash: 73.3 (#119)

| Benchmark | Claude Sonnet 5.5 | Step 3.5 Flash |
|---|---|---|
| LMArena Instruction Following | — | 1385 |

## Long Context

- Claude Sonnet 5.5: —
- Step 3.5 Flash: 42.8 (#112)

| Benchmark | Claude Sonnet 5.5 | Step 3.5 Flash |
|---|---|---|
| LMArena Longer Query | — | 1402 |

## Writing & Preference

- Claude Sonnet 5.5: —
- Step 3.5 Flash: 59.0 (#108)

| Benchmark | Claude Sonnet 5.5 | Step 3.5 Flash |
|---|---|---|
| LMArena Text | — | 1403 |
| LMArena Creative Writing | — | 1357 |
| LMArena Multi-Turn | — | 1405 |

## FAQ

### Is Claude Sonnet 5.5 better than Step 3.5 Flash?

Claude Sonnet 5.5 is the stronger model overall, scoring 60.5 to 41.7 on the Noometry Index. Step 3.5 Flash costs 27× less per token, which makes it the better buy when Claude Sonnet 5.5's lead doesn't matter for your workload.

### Which is cheaper, Claude Sonnet 5.5 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; Claude Sonnet 5.5 lists at $2 and $10.

### Is Claude Sonnet 5.5 or Step 3.5 Flash better for coding?

Claude Sonnet 5.5 scores higher on coding benchmarks: 65.5 versus 41.7 in the Noometry coding category.

### Which has the bigger context window?

Claude Sonnet 5.5 does, with 1M tokens against 256K.

### How many benchmarks do Claude Sonnet 5.5 and Step 3.5 Flash share?

0 benchmarks have published results for both models. Claude Sonnet 5.5 has 16 scored results on Noometry and Step 3.5 Flash has 19.