GPT-5.1-Codex vs GPT-5.5 Pro
GPT-5.1-Codex costs 18.0x less per output token than GPT-5.5 Pro ($10.00 vs $180.00 per million). Updated October 21, 2026; no benchmark has tested both models yet.
- Coding
- 15.3
- Overall
- No data
- Output $/M
- $10.00
- Coding
- No data
- Overall
- No data
- Output $/M
- $180.00
GPT-5.1-Codex or GPT-5.5 Pro: which to pick
Only GPT-5.1-Codex has a coding score, 15.3 on the Vibe Coding Index; GPT-5.5 Pro has none, so the two cannot be ranked on coding.
Pick GPT-5.5 Pro for a larger context window (1.05M against 400K tokens).
No benchmark has tested both yet. GPT-5.1-Codex has results on SWE-bench Verified, LMArena WebDev and LiveCodeBench (Vals AI); GPT-5.5 Pro on Epoch Capabilities Index, ARC-AGI and ARC-AGI-2. Compare them on price and context instead.
Which one for your work
Each card is decided by one number both models carry. Where only one has it, the card says so and makes no call.
Coding
Vibe Coding Index, six public coding benchmarks
No call
Only GPT-5.1-Codex has a coding score, so no call is made.
One side not measured
Intelligence
AA Intelligence Index
No call
Only GPT-5.1-Codex has a AA Intelligence Index result, 23.7.
Directional only
Web design
Design Arena: websites
No call
Only GPT-5.1-Codex has a Design Arena: websites result, 1162.
Directional only
Long documents
Listed context window
GPT-5.5 Pro
GPT-5.5 Pro takes 1.05M tokens against 400K.
Listed by OpenRouter
Everyday cost
1K input + 500 output tokens
GPT-5.1-Codex
GPT-5.1-Codex $0.0063, GPT-5.5 Pro $0.120 per turn.
List prices
Cost per solved task
One SWE-bench Verified task, solved
No call
Only GPT-5.1-Codex has the number, $0.892.
Directional only
At a glance
- Coding index
- GPT-5.1-Codex 15.3 from 2 benchmarks, GPT-5.5 Pro not benchmarked.
- Widest category
- None yet: no category has been tested on both models.
- Widest single gap
- None yet: no benchmark has tested both models.
- Output price
- GPT-5.1-Codex $10.00 against GPT-5.5 Pro $180.00 per million output tokens, 18.0x apart.
- Context window
- GPT-5.1-Codex takes 400K tokens, GPT-5.5 Pro 1.05M.
Benchmark by benchmark
Every board either model has a result on, a category to a fold; bars are each result on a 0 to 100 scale. Only one model is measured on each, so no row names a leader.
CodingDirectional onlySix of these boards feed the Vibe Coding Index9 boards measured
| Benchmark | GPT-5.1-Codex | GPT-5.5 Pro | Leader |
|---|---|---|---|
| SWE-bench Verified | 66.0% | Not measured | Only GPT-5.1-Codex measured |
| LMArena WebDev | 1337 | Not measured | Only GPT-5.1-Codex measured |
| LiveCodeBench (Vals AI) | 85.5% | Not measured | Only GPT-5.1-Codex measured |
| Vibe Code Bench (Vals AI) | 13.1% | Not measured | Only GPT-5.1-Codex measured |
| LiveCodeBench (Artificial Analysis run) | 84.9% | Not measured | Only GPT-5.1-Codex measured |
| Terminal-Bench Hard (Artificial Analysis run) | 34.8% | Not measured | Only GPT-5.1-Codex measured |
| Terminal-Bench | 57.8% | Not measured | Only GPT-5.1-Codex measured |
| ALE-Bench | 1244.9 | Not measured | Only GPT-5.1-Codex measured |
| LMArena WebDev: HTML | 1346 | Not measured | Only GPT-5.1-Codex measured |
| Neither model has a result on the other 30 boards here | |||
IntelligenceDirectional onlyPublic boards, shown as published, kept out of the index2 boards measured
| Benchmark | GPT-5.1-Codex | GPT-5.5 Pro | Leader |
|---|---|---|---|
| AA Intelligence Index | 23.7 | Not measured | Only GPT-5.1-Codex measured |
| Epoch Capabilities Index | Not measured | 162.9 | Only GPT-5.5 Pro measured |
Agentic workDirectional onlyPublic boards, shown as published, kept out of the index4 boards measured
| Benchmark | GPT-5.1-Codex | GPT-5.5 Pro | Leader |
|---|---|---|---|
| Design Arena: agents building web apps | 1018 | Not measured | Only GPT-5.1-Codex measured |
| Design Arena: agents building full-stack apps | 1086 | Not measured | Only GPT-5.1-Codex measured |
| Design Arena: agents building mobile apps | 1191 | Not measured | Only GPT-5.1-Codex measured |
| τ²-Bench Telecom | 83.0% | Not measured | Only GPT-5.1-Codex measured |
| Neither model has a result on the other 37 boards here | |||
ReasoningDirectional onlyPublic boards, shown as published, kept out of the index6 boards measured
| Benchmark | GPT-5.1-Codex | GPT-5.5 Pro | Leader |
|---|---|---|---|
| GPQA Diamond (Artificial Analysis run) | 86.0% | Not measured | Only GPT-5.1-Codex measured |
| Humanity's Last Exam (Artificial Analysis run) | 25.7% | Not measured | Only GPT-5.1-Codex measured |
| ARC-AGI | Not measured | 96.5% | Only GPT-5.5 Pro measured |
| ARC-AGI-2 | Not measured | 84.6% | Only GPT-5.5 Pro measured |
| SimpleBench | Not measured | 76.9% | Only GPT-5.5 Pro measured |
| Chess puzzles | Not measured | 62.0% | Only GPT-5.5 Pro measured |
| Neither model has a result on the other 16 boards here | |||
MathDirectional onlyPublic boards, shown as published, kept out of the index4 boards measured
| Benchmark | GPT-5.1-Codex | GPT-5.5 Pro | Leader |
|---|---|---|---|
| AA Math Index | 95.7 | Not measured | Only GPT-5.1-Codex measured |
| AIME 2025 (Artificial Analysis run) | 95.7% | Not measured | Only GPT-5.1-Codex measured |
| FrontierMath, tiers 1 to 3 | Not measured | 87.7% | Only GPT-5.5 Pro measured |
| FrontierMath, tier 4 | Not measured | 78.0% | Only GPT-5.5 Pro measured |
| Neither model has a result on the other 9 boards here | |||
KnowledgeDirectional onlyPublic boards, shown as published, kept out of the index1 board measured
| Benchmark | GPT-5.1-Codex | GPT-5.5 Pro | Leader |
|---|---|---|---|
| MMLU Pro (Artificial Analysis run) | 86.0% | Not measured | Only GPT-5.1-Codex measured |
| Neither model has a result on the other 17 boards here | |||
Web designDirectional onlyPublic boards, shown as published, kept out of the index5 boards measured
| Benchmark | GPT-5.1-Codex | GPT-5.5 Pro | Leader |
|---|---|---|---|
| Design Arena: websites | 1162 | Not measured | Only GPT-5.1-Codex measured |
| Design Arena: UI components | 1237 | Not measured | Only GPT-5.1-Codex measured |
| Design Arena: game dev | 1138 | Not measured | Only GPT-5.1-Codex measured |
| Design Arena: data viz | 1213 | Not measured | Only GPT-5.1-Codex measured |
| Design Arena: all code categories | 1152 | Not measured | Only GPT-5.1-Codex measured |
| Neither model has a result on the other 4 boards here | |||
GeneralDirectional onlyPublic boards, shown as published, kept out of the index4 boards measured
| Benchmark | GPT-5.1-Codex | GPT-5.5 Pro | Leader |
|---|---|---|---|
| IFBench | 70.0% | Not measured | Only GPT-5.1-Codex measured |
| Long context reasoning (AA-LCR) | 69.3% | Not measured | Only GPT-5.1-Codex measured |
| DTBench | Not measured | 96.0% | Only GPT-5.5 Pro measured |
| LMCA | Not measured | 53.9% | Only GPT-5.5 Pro measured |
| Neither model has a result on the other 42 boards here | |||
What each workload costs
Three fixed token mixes at each model's listed price, so per-token rates become a bill.
Chat turn
1K input + 500 output tokens
GPT-5.1-Codex costs less
Repository review
50K input + 3K output tokens
GPT-5.1-Codex costs less
Agent loop
200K input + 10K output tokens
GPT-5.1-Codex costs less
Listed OpenRouter rates, without cache or batch discounts. A workload that does not fit a model's context window would need splitting.
Specification differences
The leading value in a row is marked; a row with a missing value names no leader. Our two rows are marked in red.
| Specification | OpenAI GPT-5.1-Codex | OpenAI GPT-5.5 Pro |
|---|---|---|
| Maker | OpenAI | OpenAI |
| Weights | No public weights listed | No public weights listed |
| Released | November 13, 2025 | April 24, 2026 |
| Context window | 400K | 1.05M |
| Input $/Mtok | $1.25 | $30.00 |
| Output $/Mtok | $10.00 | $180.00 |
| Coding index | 15.3 | Not benchmarked |
| Independent measurements behind it | 2 | 0 |
| Cost per solved task | $0.892 | Not computable |
| Source | OpenRouter listing | OpenRouter listing |
Questions
Is GPT-5.1-Codex better than GPT-5.5 Pro for coding?
Only GPT-5.1-Codex has a coding score, 15.3 on the Vibe Coding Index; GPT-5.5 Pro has none, so the two cannot be ranked on coding. Pick GPT-5.5 Pro for a larger context window (1.05M against 400K tokens).
Which is cheaper, GPT-5.1-Codex or GPT-5.5 Pro?
GPT-5.1-Codex costs $1.25 per million input tokens and $10.00 per million output tokens; GPT-5.5 Pro costs $30.00 and $180.00. Cost per solved task is known for GPT-5.1-Codex only.
Which has the bigger context window, GPT-5.1-Codex or GPT-5.5 Pro?
GPT-5.5 Pro, with 1.05M tokens against 400K.
Has any benchmark tested both GPT-5.1-Codex and GPT-5.5 Pro?
No benchmark has tested both yet. GPT-5.1-Codex has results on SWE-bench Verified, LMArena WebDev and LiveCodeBench (Vals AI); GPT-5.5 Pro on Epoch Capabilities Index, ARC-AGI and ARC-AGI-2. Compare them on price and context instead. Data as of October 21, 2026.