Model comparison
GPT-5.1-Codex vs GPT-5.5 Pro
GPT-5.5 Pro is the stronger model overall, scoring 64.3 to 38.6 on the Noometry Index. GPT-5.1-Codex costs 20× less per token, which makes it the better buy when GPT-5.5 Pro's lead doesn't matter for your workload.
Last verified . 0 shared benchmarks.
Summary
- The widest gap is in math, where GPT-5.5 Pro leads 84.0 to 30.3.
- GPT-5.1-Codex is cheaper at $1.25 / $10 per million input/output tokens, against $30 / $180 for GPT-5.5 Pro.
- GPT-5.5 Pro accepts more context: 1.05M tokens versus 400K.
Side by side
| GPT-5.1-Codex | GPT-5.5 Pro | |
|---|---|---|
| Provider | OpenAI | OpenAI |
| Noometry Index | 38.6 | 64.3 |
| Released | 2025-11-12 | 2026-04-23 |
| Weights | Proprietary | Proprietary |
| Context window | 400K | 1.05M |
| Max output | 128K | 128K |
| Input $ / M tokens | $1.25 | $30 |
| Output $ / M tokens | $10 | $180 |
| Results tracked | 6 | 14 |
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Category by category
Coding Not comparable
GPT-5.1-Codex: 41.9 (#116), GPT-5.5 Pro: —
| Benchmark | GPT-5.1-Codex | GPT-5.5 Pro |
|---|---|---|
| SWE-bench Verified (bash only) | 66% | — |
| LMArena WebDev | 1337 | — |
| ALE-Bench | 1,245 | — |
Agentic & Tool Use Not comparable
GPT-5.1-Codex: 38.0 (#33), GPT-5.5 Pro: —
| Benchmark | GPT-5.1-Codex | GPT-5.5 Pro |
|---|---|---|
| Terminal-Bench | 60.4% | — |
| METR Time Horizons | 70.8% | — |
Reasoning Not comparable
GPT-5.1-Codex: —, GPT-5.5 Pro: 73.3 (#10)
| Benchmark | GPT-5.1-Codex | GPT-5.5 Pro |
|---|---|---|
| ARC-AGI-2 | — | 84.6% |
| SimpleBench | — | 76.9% |
| ARC-AGI-1 | — | 96.5% |
| CritPt | — | 30.6% |
| Chess Puzzles | — | 64% |
| DTBench | — | 96% |
| LMCA | — | 53.9% |
| Epoch Capabilities Index | — | 162.07 |
Math GPT-5.5 Pro leads
GPT-5.1-Codex: 30.3 (#235), GPT-5.5 Pro: 84.0 (#10)
| Benchmark | GPT-5.1-Codex | GPT-5.5 Pro |
|---|---|---|
| FrontierMath (Tiers 1-3) | — | 87.7% |
| FrontierMath Tier 4 | — | 78% |
| OTIS Mock AIME 2024-2025 | — | 100% |
| ProofBench | 9% | — |
| FrontierMath (Feb 2025 set) | — | 52.4% |
| FrontierMath Tier 4 (v1) | — | 39.6% |
Knowledge Not comparable
GPT-5.1-Codex: —, GPT-5.5 Pro: 64.1 (#19)
| Benchmark | GPT-5.1-Codex | GPT-5.5 Pro |
|---|---|---|
| GPQA Diamond | — | 93.9% |
Frequently asked questions
Is GPT-5.1-Codex better than GPT-5.5 Pro?
GPT-5.5 Pro is the stronger model overall, scoring 64.3 to 38.6 on the Noometry Index. GPT-5.1-Codex costs 20× less per token, which makes it the better buy when GPT-5.5 Pro's lead doesn't matter for your workload.
Which is cheaper, GPT-5.1-Codex or GPT-5.5 Pro?
GPT-5.1-Codex is cheaper. It lists at $1.25 per million input tokens and $10 per million output tokens; GPT-5.5 Pro lists at $30 and $180.
Which has the bigger context window?
GPT-5.5 Pro does, with 1.05M tokens against 400K.
How many benchmarks do GPT-5.1-Codex and GPT-5.5 Pro share?
0 benchmarks have published results for both models. GPT-5.1-Codex has 6 scored results on Noometry and GPT-5.5 Pro has 14.