Model comparison
GPT-5.5 Pro vs GPT-5-Codex
GPT-5.5 Pro is the stronger model overall, scoring 64.3 to 37.9 on the Noometry Index. GPT-5-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 reasoning, where GPT-5.5 Pro leads 73.3 to 30.9.
- GPT-5-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-5.5 Pro | GPT-5-Codex | |
|---|---|---|
| Provider | OpenAI | OpenAI |
| Noometry Index | 64.3 | 37.9 |
| Released | 2026-04-23 | 2025-09-15 |
| Weights | Proprietary | Proprietary |
| Context window | 1.05M | 400K |
| Max output | 128K | 128K |
| Input $ / M tokens | $30 | $1.25 |
| Output $ / M tokens | $180 | $10 |
| Results tracked | 14 | 3 |
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Category by category
Coding Not comparable
GPT-5.5 Pro: —, GPT-5-Codex: 42.4 (#103)
| Benchmark | GPT-5.5 Pro | GPT-5-Codex |
|---|---|---|
| WeirdML | — | 54.5% |
Agentic & Tool Use Not comparable
GPT-5.5 Pro: —, GPT-5-Codex: 31.0 (#72)
| Benchmark | GPT-5.5 Pro | GPT-5-Codex |
|---|---|---|
| Terminal-Bench | — | 44.3% |
Reasoning GPT-5.5 Pro leads
GPT-5.5 Pro: 73.3 (#10), GPT-5-Codex: 30.9 (#83)
| Benchmark | GPT-5.5 Pro | GPT-5-Codex |
|---|---|---|
| ARC-AGI-2 | 84.6% | — |
| SimpleBench | 76.9% | — |
| Kagi LLM Benchmark | — | 70.3% |
| ARC-AGI-1 | 96.5% | — |
| CritPt | 30.6% | — |
| Chess Puzzles | 64% | — |
| DTBench | 96% | — |
| LMCA | 53.9% | — |
| Epoch Capabilities Index | 162.07 | — |
Math Not comparable
GPT-5.5 Pro: 84.0 (#10), GPT-5-Codex: —
| Benchmark | GPT-5.5 Pro | GPT-5-Codex |
|---|---|---|
| FrontierMath (Tiers 1-3) | 87.7% | — |
| FrontierMath Tier 4 | 78% | — |
| OTIS Mock AIME 2024-2025 | 100% | — |
| FrontierMath (Feb 2025 set) | 52.4% | — |
| FrontierMath Tier 4 (v1) | 39.6% | — |
Knowledge Not comparable
GPT-5.5 Pro: 64.1 (#19), GPT-5-Codex: —
| Benchmark | GPT-5.5 Pro | GPT-5-Codex |
|---|---|---|
| GPQA Diamond | 93.9% | — |
Frequently asked questions
Is GPT-5.5 Pro better than GPT-5-Codex?
GPT-5.5 Pro is the stronger model overall, scoring 64.3 to 37.9 on the Noometry Index. GPT-5-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-5.5 Pro 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-5.5 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-5.5 Pro and GPT-5-Codex share?
0 benchmarks have published results for both models. GPT-5.5 Pro has 14 scored results on Noometry and GPT-5-Codex has 3.