GPT-5.5 Pro vs Grok 4.3
Grok 4.3 costs 72.0x less per output token than GPT-5.5 Pro ($2.50 vs $180.00 per million). Updated October 21, 2026; 5 benchmarks have a result for both.
GPT-5.5 Pro or Grok 4.3: which to pick
Only Grok 4.3 has a coding score, 37.4 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 1M tokens) and work measured by Chess puzzles or FrontierMath, tiers 1 to 3, where it leads.
- Shared results
- 5
- GPT-5.5 Pro only
- 4
- Grok 4.3 only
- 99
- Like-for-like categories
- 3 of 9
Only benchmarks that tested both models count toward a pick; a result only one model has is shown but not compared.
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 Grok 4.3 has a coding score, so no call is made.
One side not measured
Intelligence
AA Intelligence Index
No call
Only Grok 4.3 has a AA Intelligence Index result, 24.9.
Directional only
Agentic work
AA Agentic Index
No call
Only Grok 4.3 has a AA Agentic Index result, 15.5.
Directional only
Reasoning
GPQA Diamond
No call
Only Grok 4.3 has a GPQA Diamond result, 91.4%.
Directional only
Knowledge
MMLU Pro
No call
Only Grok 4.3 has a MMLU Pro result, 85.8%.
Directional only
Web design
Design Arena: websites
No call
Only Grok 4.3 has a Design Arena: websites result, 1196.
Directional only
Long documents
Listed context window
GPT-5.5 Pro
GPT-5.5 Pro takes 1.05M tokens against 1M.
Listed by OpenRouter
Everyday cost
1K input + 500 output tokens
Grok 4.3
GPT-5.5 Pro $0.120, Grok 4.3 $0.0025 per turn.
List prices
Cost per solved task
One SWE-bench Verified task, solved
No call
Only Grok 4.3 has the number, $0.31.
Directional only
At a glance
- Coding index
- GPT-5.5 Pro not benchmarked, Grok 4.3 37.4 from 3 benchmarks.
- Widest category
- Math, 54.2 points apart on average over 2 shared benchmarks.
- Widest single gap
- FrontierMath, tier 4: GPT-5.5 Pro 78.0% against Grok 4.3 14.6%, 63.4 points apart on a 0 to 100 scale.
- Output price
- GPT-5.5 Pro $180.00 against Grok 4.3 $2.50 per million output tokens, 72.0x apart.
- Context window
- GPT-5.5 Pro takes 1.05M tokens, Grok 4.3 1M.
Benchmark by benchmark
First the score: boards each model leads, per category, where both have a result. Then every board, a category to a fold; bars are each result on a 0 to 100 scale, so compare the two in a row, not one row with another.
| Category | GPT-5.5 Pro | Bars | Grok 4.3 | Ties |
|---|---|---|---|---|
| Reasoning | 1 | 0 | ||
| Math | 2 | 0 | ||
| General | 2 | 0 | ||
| All shared boards | 5 | 0 |
CodingDirectional onlySix of these boards feed the Vibe Coding Index18 boards, none shared
| Benchmark | GPT-5.5 Pro | Grok 4.3 | Leader |
|---|---|---|---|
| LMArena WebDev | Not measured | 1358 | Only Grok 4.3 measured |
| AA Coding Index | Not measured | 42.2 | Only Grok 4.3 measured |
| LiveCodeBench (Vals AI) | Not measured | 84.5% | Only Grok 4.3 measured |
| SWE-bench Verified (Vals AI) | Not measured | 71.4% | Only Grok 4.3 measured |
| Vibe Code Bench (Vals AI) | Not measured | 19.4% | Only Grok 4.3 measured |
| Code migration (Vals AI) | Not measured | 6.8% | Only Grok 4.3 measured |
| ProgramBench (Vals AI) | Not measured | 0.0% | Only Grok 4.3 measured |
| Terminal-Bench 2.1 (Vals AI) | Not measured | 42.0% | Only Grok 4.3 measured |
| SkillsBench (Vals AI) | Not measured | 40.6% | Only Grok 4.3 measured |
| SciCode | Not measured | 48.3% | Only Grok 4.3 measured |
| Terminal-Bench Hard (Artificial Analysis run) | Not measured | 37.9% | Only Grok 4.3 measured |
| WeirdML | Not measured | 49.9% | Only Grok 4.3 measured |
| ALE-Bench | Not measured | 944.2 | Only Grok 4.3 measured |
| LMArena Text: coding | Not measured | 1415 | Only Grok 4.3 measured |
| LMArena Text: software and IT | Not measured | 1416 | Only Grok 4.3 measured |
| LMArena WebDev: React | Not measured | 1353 | Only Grok 4.3 measured |
| LMArena WebDev: HTML | Not measured | 1367 | Only Grok 4.3 measured |
| LMArena WebDev: from an image | Not measured | 1375 | Only Grok 4.3 measured |
| Neither model has a result on the other 20 boards here | |||
IntelligenceDirectional onlyPublic boards, shown as published, kept out of the index2 boards, none shared
| Benchmark | GPT-5.5 Pro | Grok 4.3 | Leader |
|---|---|---|---|
| AA Intelligence Index | Not measured | 24.9 | Only Grok 4.3 measured |
| Epoch Capabilities Index | 162.9 | Not measured | Only GPT-5.5 Pro measured |
Agentic workDirectional onlyPublic boards, shown as published, kept out of the index16 boards, none shared
| Benchmark | GPT-5.5 Pro | Grok 4.3 | Leader |
|---|---|---|---|
| AA Agentic Index | Not measured | 15.5 | Only Grok 4.3 measured |
| Design Arena: agents building web apps | Not measured | 1126 | Only Grok 4.3 measured |
| Design Arena: agents building full-stack apps | Not measured | 1006 | Only Grok 4.3 measured |
| Design Arena: agents building mobile apps | Not measured | 1059 | Only Grok 4.3 measured |
| Design Arena: agents building Android apps | Not measured | 961 | Only Grok 4.3 measured |
| Design Arena: agents building Godot games | Not measured | 914 | Only Grok 4.3 measured |
| Design Arena: agents building games | Not measured | 1007 | Only Grok 4.3 measured |
| Design Arena: HTML slides | Not measured | 1008 | Only Grok 4.3 measured |
| Design Arena: PowerPoint slides | Not measured | 1013 | Only Grok 4.3 measured |
| Finance Agent (Vals AI) | Not measured | 37.7% | Only Grok 4.3 measured |
| Tax Agent Bench (Vals AI) | Not measured | 6.2% | Only Grok 4.3 measured |
| Legal Research Bench (Vals AI) | Not measured | 15.4% | Only Grok 4.3 measured |
| Excel Modeling Benchmark (Vals AI) | Not measured | 18.4% | Only Grok 4.3 measured |
| τ²-Bench Telecom | Not measured | 97.7% | Only Grok 4.3 measured |
| Vending-Bench 2 | Not measured | $35 | Only Grok 4.3 measured |
| LMArena Search | Not measured | 1166 | Only Grok 4.3 measured |
| Neither model has a result on the other 23 boards here | |||
ReasoningLike-for-likePublic boards, shown as published, kept out of the index10
| Benchmark | GPT-5.5 Pro | Grok 4.3 | Leader |
|---|---|---|---|
| GPQA Diamond | Not measured | 91.4% | Only Grok 4.3 measured |
| MMMU Pro (Vals AI) | Not measured | 83.1% | Only Grok 4.3 measured |
| GPQA Diamond (Artificial Analysis run) | Not measured | 90.1% | Only Grok 4.3 measured |
| Humanity's Last Exam (Artificial Analysis run) | Not measured | 37.2% | Only Grok 4.3 measured |
| GPQA Diamond (Epoch AI run) | Not measured | 88.8% | Only Grok 4.3 measured |
| ARC-AGI | 96.5% | Not measured | Only GPT-5.5 Pro measured |
| ARC-AGI-2 | 84.6% | Not measured | Only GPT-5.5 Pro measured |
| SimpleBench | 76.9% | Not measured | Only GPT-5.5 Pro measured |
| Chess puzzles | 62.0% | 18.0% | GPT-5.5 Pro |
| LMArena Text: hard prompts | Not measured | 1396 | Only Grok 4.3 measured |
| LMArena Text: expert | Not measured | 1384 | Only Grok 4.3 measured |
| LMArena Text: hard prompts in English | Not measured | 1402 | Only Grok 4.3 measured |
| LMArena Vision: diagrams | Not measured | 1241 | Only Grok 4.3 measured |
| LMArena Vision: homework | Not measured | 1241 | Only Grok 4.3 measured |
| Neither model has a result on the other 7 boards here | |||
MathLike-for-likePublic boards, shown as published, kept out of the index20
| Benchmark | GPT-5.5 Pro | Grok 4.3 | Leader |
|---|---|---|---|
| OTIS Mock AIME | Not measured | 93.3% | Only Grok 4.3 measured |
| FrontierMath, tiers 1 to 3 | 87.7% | 42.8% | GPT-5.5 Pro |
| FrontierMath, tier 4 | 78.0% | 14.6% | GPT-5.5 Pro |
| ProofBench | Not measured | 11.0% | Only Grok 4.3 measured |
| LMArena Text: math | Not measured | 1387 | Only Grok 4.3 measured |
| LMArena Text: mathematical work | Not measured | 1396 | Only Grok 4.3 measured |
| Neither model has a result on the other 7 boards here | |||
KnowledgeDirectional onlyPublic boards, shown as published, kept out of the index12 boards, none shared
| Benchmark | GPT-5.5 Pro | Grok 4.3 | Leader |
|---|---|---|---|
| MMLU Pro | Not measured | 85.8% | Only Grok 4.3 measured |
| LegalBench (Vals AI) | Not measured | 84.5% | Only Grok 4.3 measured |
| CaseLaw (Vals AI) | Not measured | 79.3% | Only Grok 4.3 measured |
| CorpFin (Vals AI) | Not measured | 68.5% | Only Grok 4.3 measured |
| TaxEval (Vals AI) | Not measured | 70.8% | Only Grok 4.3 measured |
| MortgageTax (Vals AI) | Not measured | 48.3% | Only Grok 4.3 measured |
| MedCode (Vals AI) | Not measured | 38.1% | Only Grok 4.3 measured |
| SimpleQA Verified | Not measured | 33.2% | Only Grok 4.3 measured |
| LMArena Text: science | Not measured | 1399 | Only Grok 4.3 measured |
| LMArena Text: medicine and healthcare | Not measured | 1384 | Only Grok 4.3 measured |
| LMArena Text: legal and government | Not measured | 1386 | Only Grok 4.3 measured |
| LMArena Text: business and finance | Not measured | 1381 | Only Grok 4.3 measured |
| Neither model has a result on the other 5 boards here | |||
Web designDirectional onlyPublic boards, shown as published, kept out of the index8 boards, none shared
| Benchmark | GPT-5.5 Pro | Grok 4.3 | Leader |
|---|---|---|---|
| Design Arena: websites | Not measured | 1196 | Only Grok 4.3 measured |
| Design Arena: UI components | Not measured | 1192 | Only Grok 4.3 measured |
| Design Arena: game dev | Not measured | 1174 | Only Grok 4.3 measured |
| Design Arena: data viz | Not measured | 1179 | Only Grok 4.3 measured |
| Design Arena: 3D | Not measured | 1125 | Only Grok 4.3 measured |
| Design Arena: all code categories | Not measured | 1187 | Only Grok 4.3 measured |
| Design Arena: SVG | Not measured | 1081 | Only Grok 4.3 measured |
| Design Arena: ASCII art | Not measured | 1125 | Only Grok 4.3 measured |
| Neither model has a result on the other 1 board here | |||
GeneralLike-for-likePublic boards, shown as published, kept out of the index20
| Benchmark | GPT-5.5 Pro | Grok 4.3 | Leader |
|---|---|---|---|
| Public Benefits Bench (Vals AI) | Not measured | 51.7% | Only Grok 4.3 measured |
| SAGE (Vals AI) | Not measured | 19.7% | Only Grok 4.3 measured |
| MedScribe (Vals AI) | Not measured | 74.4% | Only Grok 4.3 measured |
| Vals Multimodal Index | Not measured | 43.3% | Only Grok 4.3 measured |
| IFBench | Not measured | 83.3% | Only Grok 4.3 measured |
| Long context reasoning (AA-LCR) | Not measured | 75.0% | Only Grok 4.3 measured |
| DTBench | 96.0% | 90.7% | GPT-5.5 Pro |
| LMCA | 53.9% | 38.3% | GPT-5.5 Pro |
| LMArena Text | Not measured | 1397 | Only Grok 4.3 measured |
| LMArena Text: instruction following | Not measured | 1366 | Only Grok 4.3 measured |
| LMArena Text: creative writing | Not measured | 1380 | Only Grok 4.3 measured |
| LMArena Vision | Not measured | 1229 | Only Grok 4.3 measured |
| LMArena Text: English | Not measured | 1404 | Only Grok 4.3 measured |
| LMArena Text: non-English | Not measured | 1385 | Only Grok 4.3 measured |
| LMArena Text: Chinese | Not measured | 1422 | Only Grok 4.3 measured |
| LMArena Text: German | Not measured | 1395 | Only Grok 4.3 measured |
| LMArena Text: Japanese | Not measured | 1379 | Only Grok 4.3 measured |
| LMArena Text: Korean | Not measured | 1354 | Only Grok 4.3 measured |
| LMArena Text: French | Not measured | 1411 | Only Grok 4.3 measured |
| LMArena Text: Spanish | Not measured | 1399 | Only Grok 4.3 measured |
| LMArena Text: Russian | Not measured | 1399 | Only Grok 4.3 measured |
| LMArena Text: Polish | Not measured | 1398 | Only Grok 4.3 measured |
| LMArena Text: multi-turn | Not measured | 1406 | Only Grok 4.3 measured |
| LMArena Text: longer queries | Not measured | 1393 | Only Grok 4.3 measured |
| LMArena Text: writing and language | Not measured | 1385 | Only Grok 4.3 measured |
| LMArena Text: entertainment and media | Not measured | 1370 | Only Grok 4.3 measured |
| LMArena Vision: English | Not measured | 1235 | Only Grok 4.3 measured |
| LMArena Vision: Chinese | Not measured | 1257 | Only Grok 4.3 measured |
| LMArena Vision: reading text | Not measured | 1235 | Only Grok 4.3 measured |
| LMArena Vision: humor | Not measured | 1222 | Only Grok 4.3 measured |
| LMArena Vision: recognizing things | Not measured | 1217 | Only Grok 4.3 measured |
| LMArena Vision: creative writing | Not measured | 1237 | Only Grok 4.3 measured |
| Neither model has a result on the other 14 boards here | |||
Image generationNot comparablePublic boards, shown as published, kept out of the index0 boards, none shared
| Benchmark | GPT-5.5 Pro | Grok 4.3 | Leader |
|---|---|---|---|
| Neither model has a result on 5 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
Grok 4.3 costs less
Repository review
50K input + 3K output tokens
Grok 4.3 costs less
Agent loop
200K input + 10K output tokens
Grok 4.3 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-5.5 Pro | SpaceXAI Grok 4.3 |
|---|---|---|
| Maker | OpenAI | xAI |
| Weights | No public weights listed | No public weights listed |
| Released | April 24, 2026 | April 30, 2026 |
| Context window | 1.05M | 1M |
| Input $/Mtok | $30.00 | $1.25 |
| Output $/Mtok | $180.00 | $2.50 |
| Coding index | Not benchmarked | 37.4 |
| Independent measurements behind it | 0 | 3 |
| Cost per solved task | Not computable | $0.31 |
| Source | OpenRouter listing | OpenRouter listing |
Questions
Is GPT-5.5 Pro better than Grok 4.3 for coding?
Only Grok 4.3 has a coding score, 37.4 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 1M tokens) and work measured by Chess puzzles or FrontierMath, tiers 1 to 3, where it leads.
Which is cheaper, GPT-5.5 Pro or Grok 4.3?
GPT-5.5 Pro costs $30.00 per million input tokens and $180.00 per million output tokens; Grok 4.3 costs $1.25 and $2.50. Cost per solved task is known for Grok 4.3 only.
Which has the bigger context window, GPT-5.5 Pro or Grok 4.3?
GPT-5.5 Pro, with 1.05M tokens against 1M.
How many benchmarks is the GPT-5.5 Pro vs Grok 4.3 comparison based on?
5 benchmarks have a result for both models as of October 21, 2026. GPT-5.5 Pro's coding index rests on 0 independent benchmarks and Grok 4.3's on 3. Where only one model has a result, the page says so instead of naming a winner.