# GPT-5.1-Codex vs GPT-5-Codex

> GPT-5.1-Codex and GPT-5-Codex score almost the same on the Noometry Index (38.2 vs 37.3), so choose on price, context window or the category you care about most.

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

## Summary

- They share 1 benchmark with published results for both. GPT-5.1-Codex scores higher in 1 category and GPT-5-Codex in 1 category; one gap is clear of the uncertainty.
- The widest gap is in agentic & tool use, where GPT-5.1-Codex leads 37.8 to 30.8.
- The biggest single-benchmark swing is Terminal-Bench: 60.4% for GPT-5.1-Codex and 44.3% for GPT-5-Codex.
- Both cost about the same: $1.25 input and $10 output per million tokens.

## Snapshot

| | GPT-5.1-Codex | GPT-5-Codex |
|---|---|---|
| Provider | OpenAI | OpenAI |
| Noometry Index | 38.2 | 37.3 |
| Rank | 178 | 190 |
| Context | 400K | 400K |
| Input $/M | $1.25 | $1.25 |
| Output $/M | $10 | $10 |
| Weights | Proprietary | Proprietary |

## Coding

- GPT-5.1-Codex: 41.7 (#107)
- GPT-5-Codex: 41.9 (#100)

| Benchmark | GPT-5.1-Codex | GPT-5-Codex |
|---|---|---|
| SWE-bench Verified (bash only) | 66% | — |
| LMArena WebDev | 1337 | — |
| WeirdML | — | 54.5% |
| ALE-Bench | 1,245 | — |

## Agentic & Tool Use

- GPT-5.1-Codex: 37.8 (#32)
- GPT-5-Codex: 30.8 (#66)

| Benchmark | GPT-5.1-Codex | GPT-5-Codex |
|---|---|---|
| Terminal-Bench | 60.4% | 44.3% |
| METR Time Horizons | 70.8% | — |

## Reasoning

- GPT-5.1-Codex: —
- GPT-5-Codex: 30.0 (#80)

| Benchmark | GPT-5.1-Codex | GPT-5-Codex |
|---|---|---|
| Kagi LLM Benchmark | — | 70.3% |

## Math

- GPT-5.1-Codex: 29.3 (#218)
- GPT-5-Codex: —

| Benchmark | GPT-5.1-Codex | GPT-5-Codex |
|---|---|---|
| ProofBench | 9% | — |

## FAQ

### Is GPT-5.1-Codex better than GPT-5-Codex?

GPT-5.1-Codex and GPT-5-Codex score almost the same on the Noometry Index (38.2 vs 37.3), so choose on price, context window or the category you care about most.

### Which is cheaper, GPT-5.1-Codex or GPT-5-Codex?

GPT-5-Codex is cheaper. It lists at $1.25 per million input tokens and $10 per million output tokens; GPT-5.1-Codex lists at $1.25 and $10.

### Is GPT-5.1-Codex or GPT-5-Codex better for coding?

They score almost the same on coding (41.7 vs 41.9); test both on your own repository before choosing.

### Which has the bigger context window?

Both accept 400K tokens.

### How many benchmarks do GPT-5.1-Codex and GPT-5-Codex share?

1 benchmark has published results for both models. GPT-5.1-Codex has 6 scored results on Noometry and GPT-5-Codex has 3.