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GPT-5.5 vs Grok 4.5

Updated October 21, 2026. 116 benchmarks have a result for both. Coding is ranked on the Vibe Coding Index; every other board is shown as published.

Replace GPT-5.5 Replace Grok 4.5
GPT-5.5OpenAI
Coding
67.8
Overall
38.4
Output $/M
$30.00
82
Grok 4.5xAI
Coding
75.5
Overall
38.8
Output $/M
$6.00
34
vs boards won of 116 shared

Decision reading

Pick Grok 4.5 for coding: it scores 75.5 on the Vibe Coding Index against 67.8 for GPT-5.5.

Pick GPT-5.5 when the context window is larger, 1.05M against 500K tokens, or when what matters is AA Coding Index or Vibe Code Bench (Vals AI), where it leads.

Model AGPT-5.5OpenAI67.8/1002 independent benchmarks$1.65 per solved taskModel BGrok 4.5xAI75.5/1002 independent benchmarks$0.62 per solved task
Shared results
116
GPT-5.5 only
16
Grok 4.5 only
4
Like-for-like categories
8 of 9

Shared results can support a head-to-head reading. Results only one model has describe coverage, not superiority.

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.

At a glance

Coding index
GPT-5.5 67.8 from 2 benchmarks, Grok 4.5 75.5 from 2 benchmarks.
Widest category
Math, 19.2 points apart on average over 6 shared benchmarks.
Widest single gap
FrontierMath, tier 4: GPT-5.5 72.5% against Grok 4.5 24.4%, 48.1 points apart on a 0 to 100 scale.
Output price
GPT-5.5 $30.00 against Grok 4.5 $6.00 per million output tokens, 5.0x apart.
Context window
GPT-5.5 takes 1.05M tokens, Grok 4.5 500K.

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.

Boards won, where both have a result
CategoryGPT-5.5BarsGrok 4.5Ties
Coding118
Intelligence11
Agentic work912
Reasoning132
Math51
Knowledge101
Web design27
General312
All shared boards8234
CodingLike-for-likeFour of these boards feed the Vibe Coding Index118
Coding benchmarks for GPT-5.5 and Grok 4.5
BenchmarkGPT-5.5Grok 4.5Leader
LiveBench coding85.1%94.3%Grok 4.5
LMArena WebDev15131553Grok 4.5
AA Coding Index74.972.4GPT-5.5
LiveCodeBench (Vals AI)85.3%87.3%Grok 4.5
SWE-bench Verified (Vals AI)82.6%86.6%Grok 4.5
Terminal-Bench 4 (Vals AI)Not measured8.6%Only Grok 4.5 measured
Vibe Code Bench (Vals AI)69.8%69.0%GPT-5.5
Code migration (Vals AI)45.2%36.6%GPT-5.5
ProgramBench (Vals AI)0.5%0.0%GPT-5.5
IOI (Vals AI)Not measured40.6%Only Grok 4.5 measured
Terminal-Bench 2.1 (Vals AI)76.4%67.8%GPT-5.5
SkillsBench (Vals AI)62.5%66.0%Grok 4.5
CyberBench (Vals AI)Not measured71.0%Only Grok 4.5 measured
SciCode56.1%55.0%GPT-5.5
Terminal-Bench Hard (Artificial Analysis run)60.6%Not measuredOnly GPT-5.5 measured
Terminal-Bench84.7%Not measuredOnly GPT-5.5 measured
FrontierCode43.0%42.4%GPT-5.5
GSO-Bench40.2%Not measuredOnly GPT-5.5 measured
WeirdML84.9%46.4%GPT-5.5
MirrorCode10.0%Not measuredOnly GPT-5.5 measured
ALE-Bench1943.01309.3GPT-5.5
LMArena Text: coding14941474GPT-5.5
LMArena Text: software and IT14931471GPT-5.5
LMArena WebDev: React15061556Grok 4.5
LMArena WebDev: HTML15431567Grok 4.5
LMArena WebDev: from an image15321562Grok 4.5
Neither model has a result on the other 12 boards here
IntelligenceLike-for-likePublic boards, shown as published, kept out of the index11
Intelligence benchmarks for GPT-5.5 and Grok 4.5
BenchmarkGPT-5.5Grok 4.5Leader
AA Intelligence Index38.438.8Grok 4.5
Epoch Capabilities Index159.7154.1GPT-5.5
Agentic workLike-for-likePublic boards, shown as published, kept out of the index912
Agentic work benchmarks for GPT-5.5 and Grok 4.5
BenchmarkGPT-5.5Grok 4.5Leader
AA Agentic Index36.441.2Grok 4.5
Design Arena: agents building web apps11171217Grok 4.5
Design Arena: agents building full-stack apps10891249Grok 4.5
Design Arena: agents building mobile apps11431221Grok 4.5
Design Arena: agents building Android apps11691242Grok 4.5
Design Arena: agents building Godot games11731229Grok 4.5
Design Arena: agents building games11791235Grok 4.5
Design Arena: HTML slides10671204Grok 4.5
Design Arena: PowerPoint slides11081232Grok 4.5
LiveBench research61.6%85.9%Grok 4.5
LiveBench browser48.0%44.0%GPT-5.5
LiveBench long agentic44.6%27.9%GPT-5.5
SREBench (Vals AI)3.8%0.8%GPT-5.5
Finance Agent (Vals AI)51.8%48.4%GPT-5.5
Tax Agent Bench (Vals AI)21.8%24.9%Grok 4.5
Legal Research Bench (Vals AI)40.4%38.0%GPT-5.5
Excel Modeling Benchmark (Vals AI)64.5%52.9%GPT-5.5
Time Horizon Index (Vals AI)8.3%6.3%GPT-5.5
τ²-Bench Telecom93.9%Not measuredOnly GPT-5.5 measured
APEX-Agents55.1%56.2%Grok 4.5
Remote Labor Index6.3%Not measuredOnly GPT-5.5 measured
OSWorld 2.013.0%Not measuredOnly GPT-5.5 measured
DeepResearch Bench54.0%Not measuredOnly GPT-5.5 measured
PostTrainBench27.2%23.4%GPT-5.5
Vending-Bench 2$7,524$3,887GPT-5.5
LMArena SearchNot measured1216Only Grok 4.5 measured
Neither model has a result on the other 13 boards here
ReasoningLike-for-likePublic boards, shown as published, kept out of the index132
Reasoning benchmarks for GPT-5.5 and Grok 4.5
BenchmarkGPT-5.5Grok 4.5Leader
GPQA Diamond93.2%92.9%GPT-5.5
LiveBench reasoning89.7%87.2%GPT-5.5
MMMU Pro (Vals AI)88.3%61.8%GPT-5.5
GPQA Diamond (Artificial Analysis run)93.5%93.1%GPT-5.5
Humanity's Last Exam (Artificial Analysis run)45.8%42.7%GPT-5.5
GPQA Diamond (Epoch AI run)90.7%93.4%Grok 4.5
ARC-AGI95.0%87.2%GPT-5.5
ARC-AGI-285.0%52.6%GPT-5.5
SimpleBench69.0%70.0%Grok 4.5
Chess puzzles63.0%35.0%GPT-5.5
Mystery game puzzles56.0%Not measuredOnly GPT-5.5 measured
EBR-bench34.3%Not measuredOnly GPT-5.5 measured
LMArena Text: hard prompts14891462GPT-5.5
LMArena Text: expert15071465GPT-5.5
LMArena Text: hard prompts in English14831464GPT-5.5
LMArena Vision: diagrams13251304GPT-5.5
LMArena Vision: homework13321295GPT-5.5
Neither model has a result on the other 4 boards here
MathLike-for-likePublic boards, shown as published, kept out of the index51
Math benchmarks for GPT-5.5 and Grok 4.5
BenchmarkGPT-5.5Grok 4.5Leader
OTIS Mock AIME84.4%97.8%Grok 4.5
FrontierMath, tiers 1 to 385.3%57.2%GPT-5.5
FrontierMath, tier 472.5%24.4%GPT-5.5
ProofBench50.0%31.0%GPT-5.5
LMArena Text: math14871460GPT-5.5
LMArena Text: mathematical work14961482GPT-5.5
Neither model has a result on the other 7 boards here
KnowledgeLike-for-likePublic boards, shown as published, kept out of the index101
Knowledge benchmarks for GPT-5.5 and Grok 4.5
BenchmarkGPT-5.5Grok 4.5Leader
MMLU Pro88.1%89.2%Grok 4.5
LegalBench (Vals AI)86.5%86.0%GPT-5.5
CaseLaw (Vals AI)66.2%Not measuredOnly GPT-5.5 measured
CorpFin (Vals AI)68.4%67.4%GPT-5.5
TaxEval (Vals AI)75.0%71.7%GPT-5.5
MortgageTax (Vals AI)68.8%61.8%GPT-5.5
MedCode (Vals AI)49.1%43.3%GPT-5.5
SimpleQA Verified63.0%48.3%GPT-5.5
LMArena Text: science14851464GPT-5.5
LMArena Text: medicine and healthcare14651440GPT-5.5
LMArena Text: legal and government14911463GPT-5.5
LMArena Text: business and finance14781441GPT-5.5
Neither model has a result on the other 5 boards here
Web designLike-for-likePublic boards, shown as published, kept out of the index27
Web design benchmarks for GPT-5.5 and Grok 4.5
BenchmarkGPT-5.5Grok 4.5Leader
Design Arena: websites12561281Grok 4.5
Design Arena: UI components12601279Grok 4.5
Design Arena: game dev12941263GPT-5.5
Design Arena: data viz12651267Grok 4.5
Design Arena: 3D11981257Grok 4.5
Design Arena: all code categories12601276Grok 4.5
Design Arena: SVG12341215GPT-5.5
Design Arena: ASCII art12541257Grok 4.5
LiveBench design70.3%78.1%Grok 4.5
GeneralLike-for-likePublic boards, shown as published, kept out of the index312
General benchmarks for GPT-5.5 and Grok 4.5
BenchmarkGPT-5.5Grok 4.5Leader
LiveBench data analysis81.6%73.0%GPT-5.5
Public Benefits Bench (Vals AI)60.9%Not measuredOnly GPT-5.5 measured
SAGE (Vals AI)51.5%35.0%GPT-5.5
MedScribe (Vals AI)86.9%86.9%Grok 4.5
Vals Multimodal Index68.1%63.4%GPT-5.5
IFBench75.9%Not measuredOnly GPT-5.5 measured
Long context reasoning (AA-LCR)84.3%79.3%GPT-5.5
DTBench96.0%96.5%Grok 4.5
LMCA54.3%45.2%GPT-5.5
Surface Evolver Bench88.1%74.4%GPT-5.5
Furniture assembly44.2%22.5%GPT-5.5
ExploitBench47.4%Not measuredOnly GPT-5.5 measured
CL-bench Life22.2%Not measuredOnly GPT-5.5 measured
LMArena Text14711448GPT-5.5
LMArena Text: instruction following14781445GPT-5.5
LMArena Text: creative writing14551442GPT-5.5
LMArena Vision12971287GPT-5.5
LMArena Text: English14701453GPT-5.5
LMArena Text: non-English14671440GPT-5.5
LMArena Text: Chinese15341495GPT-5.5
LMArena Text: German14801448GPT-5.5
LMArena Text: Japanese14991430GPT-5.5
LMArena Text: Korean14601406GPT-5.5
LMArena Text: French14851457GPT-5.5
LMArena Text: Spanish14681451GPT-5.5
LMArena Text: Russian14731449GPT-5.5
LMArena Text: Polish14651432GPT-5.5
LMArena Text: multi-turn14761456GPT-5.5
LMArena Text: longer queries14841462GPT-5.5
LMArena Text: writing and language14661445GPT-5.5
LMArena Text: entertainment and media14491434GPT-5.5
LMArena Vision: English12921285GPT-5.5
LMArena Vision: Chinese13601345GPT-5.5
LMArena Vision: reading text13061293GPT-5.5
LMArena Vision: humor12931276GPT-5.5
LMArena Vision: recognizing things1231Not measuredOnly GPT-5.5 measured
LMArena Vision: creative writing13011293GPT-5.5
LMArena Document14861452GPT-5.5
Neither model has a result on the other 8 boards here
Image generationNot comparablePublic boards, shown as published, kept out of the index0 boards, none shared
Image generation benchmarks for GPT-5.5 and Grok 4.5
BenchmarkGPT-5.5Grok 4.5Leader
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

GPT-5.5$0.020Fits in one request
Grok 4.5$0.0050Fits in one request

Grok 4.5 costs less

Repository review

50K input + 3K output tokens

GPT-5.5$0.340Fits in one request
Grok 4.5$0.118Fits in one request

Grok 4.5 costs less

Agent loop

200K input + 10K output tokens

GPT-5.5$1.30Fits in one request
Grok 4.5$0.460Fits in one request

Grok 4.5 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.

Specifications of GPT-5.5 and Grok 4.5
SpecificationOpenAI GPT-5.5SpaceXAI Grok 4.5
MakerOpenAIxAI
WeightsNo public weights listedNo public weights listed
ReleasedApril 24, 2026July 8, 2026
Context window1.05M500K
Input $/Mtok$5.00$2.00
Output $/Mtok$30.00$6.00
Coding index67.875.5
Independent measurements behind it22
Cost per solved task$1.65$0.62
SourceOpenRouter listingOpenRouter listing

Questions

Is GPT-5.5 better than Grok 4.5 for coding?

Pick Grok 4.5 for coding: it scores 75.5 on the Vibe Coding Index against 67.8 for GPT-5.5. Pick GPT-5.5 when the context window is larger, 1.05M against 500K tokens, or when what matters is AA Coding Index or Vibe Code Bench (Vals AI), where it leads.

Which is cheaper, GPT-5.5 or Grok 4.5?

GPT-5.5 costs $5.00 per million input tokens and $30.00 per million output tokens; Grok 4.5 costs $2.00 and $6.00. Per solved SWE-bench Verified task, GPT-5.5 costs $1.65 and Grok 4.5 $0.62.

Which has the bigger context window, GPT-5.5 or Grok 4.5?

GPT-5.5, with 1.05M tokens against 500K.

How many benchmarks is the GPT-5.5 vs Grok 4.5 comparison based on?

116 benchmarks have a result for both models as of October 21, 2026. GPT-5.5's coding index rests on 2 independent benchmarks and Grok 4.5's on 2. Where only one model has a result, the page says so instead of naming a winner.

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