# Mercury 2.5 vs Step 3.5 Flash

> Step 3.5 Flash is the stronger model overall, scoring 42.3 to 33.5 on the Noometry Index. Mercury 2.5 costs 2.2× less per token, which makes it the better buy when Step 3.5 Flash's lead doesn't matter for your workload.

- Canonical page: https://noometry.com/compare/mercury-2-5-vs-step-3-5-flash
- Last updated: 2026-10-11
- Shared benchmarks: 0

## Summary

- The widest gap is in math, where Step 3.5 Flash leads 42.6 to 23.3.
- Mercury 2.5 is cheaper at $0.04 / $0.15 per million input/output tokens, against $0.10 / $0.30 for Step 3.5 Flash.
- Mercury 2.5 accepts more context: 260K tokens versus 256K.
- Step 3.5 Flash has downloadable open weights; the other is API-only.

## Snapshot

| | Mercury 2.5 | Step 3.5 Flash |
|---|---|---|
| Provider | Inception | StepFun |
| Noometry Index | 33.5 | 42.3 |
| Rank | 242 | 116 |
| Context | 260K | 256K |
| Input $/M | $0.04 | $0.10 |
| Output $/M | $0.15 | $0.30 |
| Weights | Proprietary | Open |

## Coding

- Mercury 2.5: 39.5 (#156)
- Step 3.5 Flash: 42.4 (#105)

| Benchmark | Mercury 2.5 | Step 3.5 Flash |
|---|---|---|
| SciCode | 38.5% | — |
| LMArena Coding | — | 1436 |
| ALE-Bench | 301.65 | — |

## Reasoning

- Mercury 2.5: 22.4 (#193)
- Step 3.5 Flash: 22.2 (#202)

| Benchmark | Mercury 2.5 | Step 3.5 Flash |
|---|---|---|
| NYT Connections (extended) | — | 28.4% |
| CritPt | 0% | — |
| LMArena Hard Prompts | — | 1411 |

## Math

- Mercury 2.5: 23.3 (#272)
- Step 3.5 Flash: 42.6 (#84)

| Benchmark | Mercury 2.5 | Step 3.5 Flash |
|---|---|---|
| MathArena Final-Answer Competitions | — | 66.8% |
| ProofBench | 3% | — |
| LMArena Math | — | 1408 |

## Knowledge

- Mercury 2.5: —
- Step 3.5 Flash: 39.6 (#132)

| Benchmark | Mercury 2.5 | Step 3.5 Flash |
|---|---|---|
| LMArena Expert | — | 1421 |

## Multilingual

- Mercury 2.5: —
- Step 3.5 Flash: 50.5 (#119)

| Benchmark | Mercury 2.5 | 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

- Mercury 2.5: —
- Step 3.5 Flash: 73.1 (#124)

| Benchmark | Mercury 2.5 | Step 3.5 Flash |
|---|---|---|
| LMArena Instruction Following | — | 1385 |

## Long Context

- Mercury 2.5: —
- Step 3.5 Flash: 42.8 (#117)

| Benchmark | Mercury 2.5 | Step 3.5 Flash |
|---|---|---|
| LMArena Longer Query | — | 1402 |

## Writing & Preference

- Mercury 2.5: —
- Step 3.5 Flash: 58.8 (#113)

| Benchmark | Mercury 2.5 | Step 3.5 Flash |
|---|---|---|
| LMArena Text | — | 1403 |
| LMArena Creative Writing | — | 1357 |
| LMArena Multi-Turn | — | 1405 |

## FAQ

### Is Mercury 2.5 better than Step 3.5 Flash?

Step 3.5 Flash is the stronger model overall, scoring 42.3 to 33.5 on the Noometry Index. Mercury 2.5 costs 2.2× less per token, which makes it the better buy when Step 3.5 Flash's lead doesn't matter for your workload.

### Which is cheaper, Mercury 2.5 or Step 3.5 Flash?

Mercury 2.5 is cheaper. It lists at $0.04 per million input tokens and $0.15 per million output tokens; Step 3.5 Flash lists at $0.10 and $0.30.

### Is Mercury 2.5 or Step 3.5 Flash better for coding?

Step 3.5 Flash scores higher on coding benchmarks: 42.4 versus 39.5 in the Noometry coding category.

### Which has the bigger context window?

Mercury 2.5 does, with 260K tokens against 256K.

### How many benchmarks do Mercury 2.5 and Step 3.5 Flash share?

0 benchmarks have published results for both models. Mercury 2.5 has 4 scored results on Noometry and Step 3.5 Flash has 19.