# GPT-5.1-Codex vs Phi-4 Mini

> GPT-5.1-Codex is the stronger model overall, scoring 38.2 to 30.4 on the Noometry Index. Phi-4 Mini costs 26× less per token, which makes it the better buy when GPT-5.1-Codex's lead doesn't matter for your workload.

- Canonical page: https://noometry.com/compare/gpt-5-1-codex-vs-phi-4-mini
- Last updated: 2026-10-10
- Shared benchmarks: 0

## Summary

- The widest gap is in coding, where GPT-5.1-Codex leads 41.7 to 27.6.
- Phi-4 Mini is cheaper at $0.075 / $0.30 per million input/output tokens, against $1.25 / $10 for GPT-5.1-Codex.
- GPT-5.1-Codex accepts more context: 400K tokens versus 128K.
- Phi-4 Mini has downloadable open weights; the other is API-only.

## Snapshot

| | GPT-5.1-Codex | Phi-4 Mini |
|---|---|---|
| Provider | OpenAI | Microsoft |
| Noometry Index | 38.2 | 30.4 |
| Rank | 178 | 280 |
| Context | 400K | 128K |
| Input $/M | $1.25 | $0.075 |
| Output $/M | $10 | $0.30 |
| Weights | Proprietary | Open |

## Coding

- GPT-5.1-Codex: 41.7 (#107)
- Phi-4 Mini: 27.6 (#312)

| Benchmark | GPT-5.1-Codex | Phi-4 Mini |
|---|---|---|
| SWE-bench Verified (bash only) | 66% | — |
| LMArena WebDev | 1337 | — |
| SciCode | — | 10.8% |
| ALE-Bench | 1,245 | — |

## Agentic & Tool Use

- GPT-5.1-Codex: 37.8 (#32)
- Phi-4 Mini: —

| Benchmark | GPT-5.1-Codex | Phi-4 Mini |
|---|---|---|
| Terminal-Bench | 60.4% | — |
| METR Time Horizons | 70.8% | — |

## Reasoning

- GPT-5.1-Codex: —
- Phi-4 Mini: 21.7 (#190)

| Benchmark | GPT-5.1-Codex | Phi-4 Mini |
|---|---|---|
| CritPt | — | 0% |

## Math

- GPT-5.1-Codex: 29.3 (#218)
- Phi-4 Mini: —

| Benchmark | GPT-5.1-Codex | Phi-4 Mini |
|---|---|---|
| ProofBench | 9% | — |

## Knowledge

- GPT-5.1-Codex: —
- Phi-4 Mini: 24.8 (#261)

| Benchmark | GPT-5.1-Codex | Phi-4 Mini |
|---|---|---|
| Vectara Hallucination Rate | — | 23.5% |

## FAQ

### Is GPT-5.1-Codex better than Phi-4 Mini?

GPT-5.1-Codex is the stronger model overall, scoring 38.2 to 30.4 on the Noometry Index. Phi-4 Mini costs 26× less per token, which makes it the better buy when GPT-5.1-Codex's lead doesn't matter for your workload.

### Which is cheaper, GPT-5.1-Codex or Phi-4 Mini?

Phi-4 Mini is cheaper. It lists at $0.075 per million input tokens and $0.30 per million output tokens; GPT-5.1-Codex lists at $1.25 and $10.

### Is GPT-5.1-Codex or Phi-4 Mini better for coding?

GPT-5.1-Codex scores higher on coding benchmarks: 41.7 versus 27.6 in the Noometry coding category.

### Which has the bigger context window?

GPT-5.1-Codex does, with 400K tokens against 128K.

### How many benchmarks do GPT-5.1-Codex and Phi-4 Mini share?

0 benchmarks have published results for both models. GPT-5.1-Codex has 6 scored results on Noometry and Phi-4 Mini has 3.