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Gemini 3.8 Flash vs Grok 4.5

Gemini 3.8 Flash leads Grok 4.5 on coding, 61.6 to 58.6 on the Vibe Coding Index, and Gemini 3.8 Flash costs 1.6x less per output token ($3.75 vs $6.00 per million). Updated October 21, 2026; 114 benchmarks have a result for both.

Replace Gemini 3.8 Flash Replace Grok 4.5
Gemini 3.8 FlashGoogle
Coding
61.6
Overall
69.0
Output $/M
$3.75
97
Grok 4.5xAI
Coding
58.6
Overall
62.1
Output $/M
$6.00
17
vs boards won of 114 shared

Gemini 3.8 Flash or Grok 4.5: which to pick

Pick Gemini 3.8 Flash for coding: it scores 61.6 on the Vibe Coding Index against 58.6 for Grok 4.5.

Pick Grok 4.5 for a lower cost per solved task ($0.62 against $2.74) and work measured by LiveBench coding or SWE-bench Verified (Vals AI), where it leads.

Model AGemini 3.8 FlashGoogle61.6/1006 independent benchmarks$2.74 per solved taskModel BGrok 4.5xAI58.6/1006 independent benchmarks$0.62 per solved task
Shared results
114
Gemini 3.8 Flash only
14
Grok 4.5 only
9
Like-for-like categories
8 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.

At a glance

Coding index
Gemini 3.8 Flash 61.6 from 6 benchmarks, Grok 4.5 58.6 from 6 benchmarks.
Widest category
Reasoning, 10.8 points apart on average over 14 shared benchmarks.
Widest single gap
WeirdML: Gemini 3.8 Flash 84.8% against Grok 4.5 46.4%, 38.4 points apart on a 0 to 100 scale.
Output price
Gemini 3.8 Flash $3.75 against Grok 4.5 $6.00 per million output tokens, 1.6x apart.
Context window
Gemini 3.8 Flash 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
CategoryGemini 3.8 FlashBarsGrok 4.5Ties
Coding167
Intelligence20
Agentic work135
Reasoning140
Math51
Knowledge110
Web design81
General283
All shared boards9717
CodingLike-for-likeSix of these boards feed the Vibe Coding Index167
Coding benchmarks for Gemini 3.8 Flash and Grok 4.5
BenchmarkGemini 3.8 FlashGrok 4.5Leader
LiveBench coding82.2%94.3%Grok 4.5
LMArena WebDev15851553Gemini 3.8 Flash
AA Coding Index76.372.4Gemini 3.8 Flash
LiveCodeBench (Vals AI)89.5%87.3%Gemini 3.8 Flash
SWE-bench Verified (Vals AI)80.0%86.6%Grok 4.5
Terminal-Bench 4 (Vals AI)19.7%8.6%Gemini 3.8 Flash
Vibe Code Bench (Vals AI)78.7%69.0%Gemini 3.8 Flash
Code migration (Vals AI)36.5%36.6%Grok 4.5
ProgramBench (Vals AI)1.0%0.0%Gemini 3.8 Flash
IOI (Vals AI)56.9%40.6%Gemini 3.8 Flash
Terminal-Bench 2.1 (Vals AI)81.3%67.8%Gemini 3.8 Flash
SWE-bench Multimodal (Vals AI)40.8%Not measuredOnly Gemini 3.8 Flash measured
Vibe Code Bench 1-100 (Vals AI)18.8%Not measuredOnly Gemini 3.8 Flash measured
SkillsBench (Vals AI)58.0%66.0%Grok 4.5
CyberBench (Vals AI)43.8%71.0%Grok 4.5
SciCode56.6%55.0%Gemini 3.8 Flash
FrontierCode41.2%42.4%Grok 4.5
FrontierSWE19.6%Not measuredOnly Gemini 3.8 Flash measured
WeirdML84.8%46.4%Gemini 3.8 Flash
ALE-Bench1269.71309.3Grok 4.5
LMArena Text: coding15081474Gemini 3.8 Flash
LMArena Text: software and IT15071471Gemini 3.8 Flash
LMArena WebDev: React15771556Gemini 3.8 Flash
LMArena WebDev: HTML16161567Gemini 3.8 Flash
LMArena WebDev: from an image15931562Gemini 3.8 Flash
SciCode12.3%6.5%Gemini 3.8 Flash
Neither model has a result on the other 13 boards here
IntelligenceLike-for-likePublic boards, shown as published, kept out of the index20
Intelligence benchmarks for Gemini 3.8 Flash and Grok 4.5
BenchmarkGemini 3.8 FlashGrok 4.5Leader
AA Intelligence Index40.938.8Gemini 3.8 Flash
Epoch Capabilities Index157.4154.1Gemini 3.8 Flash
Agentic workLike-for-likePublic boards, shown as published, kept out of the index135
Agentic work benchmarks for Gemini 3.8 Flash and Grok 4.5
BenchmarkGemini 3.8 FlashGrok 4.5Leader
AA Agentic Index40.241.2Grok 4.5
Design Arena: agents building web apps12381218Gemini 3.8 Flash
Design Arena: agents building full-stack apps12441249Grok 4.5
Design Arena: agents building mobile apps12361221Gemini 3.8 Flash
Design Arena: agents building Android apps10741242Grok 4.5
Design Arena: agents building Godot games12731229Gemini 3.8 Flash
Design Arena: agents building gamesNot measured1236Only Grok 4.5 measured
Design Arena: HTML slidesNot measured1204Only Grok 4.5 measured
Design Arena: PowerPoint slides11771233Grok 4.5
Design Arena: spreadsheets1056Not measuredOnly Gemini 3.8 Flash measured
LiveBench research79.1%85.9%Grok 4.5
LiveBench browser64.0%44.0%Gemini 3.8 Flash
LiveBench long agentic30.1%27.9%Gemini 3.8 Flash
SREBench (Vals AI)11.1%0.8%Gemini 3.8 Flash
Finance Agent (Vals AI)61.4%48.4%Gemini 3.8 Flash
Tax Agent Bench (Vals AI)32.1%24.9%Gemini 3.8 Flash
Legal Research Bench (Vals AI)38.9%38.0%Gemini 3.8 Flash
Harvey's Legal Agent Benchmark (Vals AI)12.1%Not measuredOnly Gemini 3.8 Flash measured
Excel Modeling Benchmark (Vals AI)72.2%52.9%Gemini 3.8 Flash
BioMysteryBench (Vals AI)62.2%Not measuredOnly Gemini 3.8 Flash measured
Terminal-Bench-Science (Vals AI)8.6%Not measuredOnly Gemini 3.8 Flash measured
Vals Science Index35.8%Not measuredOnly Gemini 3.8 Flash measured
Time Horizon Index (Vals AI)18.8%6.3%Gemini 3.8 Flash
CUA-bench (Vals AI)4.2%Not measuredOnly Gemini 3.8 Flash measured
APEX-Agents64.3%56.2%Gemini 3.8 Flash
Remote Labor Index5.8%Not measuredOnly Gemini 3.8 Flash measured
PostTrainBenchNot measured23.4%Only Grok 4.5 measured
Vending-Bench 2$5,094$3,887Gemini 3.8 Flash
LMArena SearchNot measured1216Only Grok 4.5 measured
Neither model has a result on the other 12 boards here
ReasoningLike-for-likePublic boards, shown as published, kept out of the index140
Reasoning benchmarks for Gemini 3.8 Flash and Grok 4.5
BenchmarkGemini 3.8 FlashGrok 4.5Leader
GPQA Diamond94.4%92.9%Gemini 3.8 Flash
LiveBench reasoning89.3%87.2%Gemini 3.8 Flash
MysteryMechanism (Vals AI)36.5%Not measuredOnly Gemini 3.8 Flash measured
MMMU Pro (Vals AI)89.1%61.8%Gemini 3.8 Flash
GPQA Diamond (Artificial Analysis run)95.3%93.1%Gemini 3.8 Flash
Humanity's Last Exam (Artificial Analysis run)47.8%42.7%Gemini 3.8 Flash
GPQA Diamond (Epoch AI run)95.4%93.4%Gemini 3.8 Flash
ARC-AGI98.5%87.2%Gemini 3.8 Flash
ARC-AGI-289.2%52.6%Gemini 3.8 Flash
SimpleBenchNot measured70.0%Only Grok 4.5 measured
Chess puzzles58.0%35.0%Gemini 3.8 Flash
Mystery game puzzles47.0%Not measuredOnly Gemini 3.8 Flash measured
LMArena Text: hard prompts15091462Gemini 3.8 Flash
LMArena Text: expert15261465Gemini 3.8 Flash
LMArena Text: hard prompts in English15041464Gemini 3.8 Flash
LMArena Vision: diagrams13451304Gemini 3.8 Flash
LMArena Vision: homework13511295Gemini 3.8 Flash
Kagi LLM BenchmarkNot measured83.5%Only Grok 4.5 measured
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 Gemini 3.8 Flash and Grok 4.5
BenchmarkGemini 3.8 FlashGrok 4.5Leader
OTIS Mock AIME98.9%97.8%Gemini 3.8 Flash
FrontierMath, tiers 1 to 368.4%57.2%Gemini 3.8 Flash
FrontierMath, tier 422.0%24.4%Grok 4.5
ProofBench48.0%31.0%Gemini 3.8 Flash
LMArena Text: math15321460Gemini 3.8 Flash
LMArena Text: mathematical work15191482Gemini 3.8 Flash
Neither model has a result on the other 7 boards here
KnowledgeLike-for-likePublic boards, shown as published, kept out of the index110
Knowledge benchmarks for Gemini 3.8 Flash and Grok 4.5
BenchmarkGemini 3.8 FlashGrok 4.5Leader
MMLU Pro90.2%89.2%Gemini 3.8 Flash
LegalBench (Vals AI)87.0%86.0%Gemini 3.8 Flash
CorpFin (Vals AI)Not measured67.4%Only Grok 4.5 measured
TaxEval (Vals AI)74.5%71.7%Gemini 3.8 Flash
MortgageTax (Vals AI)65.3%61.8%Gemini 3.8 Flash
MedCode (Vals AI)48.1%43.3%Gemini 3.8 Flash
SimpleQA Verified69.7%48.3%Gemini 3.8 Flash
LMArena Text: science15231464Gemini 3.8 Flash
LMArena Text: medicine and healthcare15081440Gemini 3.8 Flash
LMArena Text: legal and government14971463Gemini 3.8 Flash
LMArena Text: business and finance14791441Gemini 3.8 Flash
FACTS Benchmark Suite69.4%50.2%Gemini 3.8 Flash
Neither model has a result on the other 6 boards here
Web designLike-for-likePublic boards, shown as published, kept out of the index81
Web design benchmarks for Gemini 3.8 Flash and Grok 4.5
BenchmarkGemini 3.8 FlashGrok 4.5Leader
Design Arena: websites13001281Gemini 3.8 Flash
Design Arena: UI components13191279Gemini 3.8 Flash
Design Arena: game dev13051263Gemini 3.8 Flash
Design Arena: data viz12691266Gemini 3.8 Flash
Design Arena: 3D12951257Gemini 3.8 Flash
Design Arena: all code categories13041275Gemini 3.8 Flash
Design Arena: SVG12951215Gemini 3.8 Flash
Design Arena: ASCII art12651257Gemini 3.8 Flash
LiveBench design72.7%78.1%Grok 4.5
GeneralLike-for-likePublic boards, shown as published, kept out of the index283
General benchmarks for Gemini 3.8 Flash and Grok 4.5
BenchmarkGemini 3.8 FlashGrok 4.5Leader
Vals Index56.0%Not measuredOnly Gemini 3.8 Flash measured
LiveBench data analysis54.0%73.0%Grok 4.5
Public Benefits Bench (Vals AI)65.3%Not measuredOnly Gemini 3.8 Flash measured
SAGE (Vals AI)35.1%35.0%Gemini 3.8 Flash
MedScribe (Vals AI)84.5%86.9%Grok 4.5
Vals Multimodal IndexNot measured63.4%Only Grok 4.5 measured
Long context reasoning (AA-LCR)84.0%79.3%Gemini 3.8 Flash
DTBench95.7%96.5%Grok 4.5
LMCA52.9%45.2%Gemini 3.8 Flash
Surface Evolver Bench76.9%74.4%Gemini 3.8 Flash
Furniture assembly31.7%22.5%Gemini 3.8 Flash
LMArena Text14991448Gemini 3.8 Flash
LMArena Text: instruction following14921445Gemini 3.8 Flash
LMArena Text: creative writing14881442Gemini 3.8 Flash
LMArena Vision13151287Gemini 3.8 Flash
LMArena Text: English14981453Gemini 3.8 Flash
LMArena Text: non-English14911440Gemini 3.8 Flash
LMArena Text: Chinese15531495Gemini 3.8 Flash
LMArena Text: German15011448Gemini 3.8 Flash
LMArena Text: Japanese15071430Gemini 3.8 Flash
LMArena Text: Korean14641406Gemini 3.8 Flash
LMArena Text: French14961457Gemini 3.8 Flash
LMArena Text: Spanish14871451Gemini 3.8 Flash
LMArena Text: Russian15141449Gemini 3.8 Flash
LMArena Text: Polish14971432Gemini 3.8 Flash
LMArena Text: multi-turn15031456Gemini 3.8 Flash
LMArena Text: longer queries15071462Gemini 3.8 Flash
LMArena Text: writing and language14941445Gemini 3.8 Flash
LMArena Text: entertainment and media14801434Gemini 3.8 Flash
LMArena Vision: English13181285Gemini 3.8 Flash
LMArena Vision: Chinese14161345Gemini 3.8 Flash
LMArena Vision: reading text13331293Gemini 3.8 Flash
LMArena Vision: humor13211276Gemini 3.8 Flash
LMArena Vision: creative writing12991293Gemini 3.8 Flash
LMArena DocumentNot measured1452Only Grok 4.5 measured
Neither model has a result on the other 11 boards here
Image generationNot comparablePublic boards, shown as published, kept out of the index0 boards, none shared
Image generation benchmarks for Gemini 3.8 Flash and Grok 4.5
BenchmarkGemini 3.8 FlashGrok 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

Gemini 3.8 Flash$0.0026Fits in one request
Grok 4.5$0.0050Fits in one request

Gemini 3.8 Flash costs less

Repository review

50K input + 3K output tokens

Gemini 3.8 Flash$0.049Fits in one request
Grok 4.5$0.118Fits in one request

Gemini 3.8 Flash costs less

Agent loop

200K input + 10K output tokens

Gemini 3.8 Flash$0.188Fits in one request
Grok 4.5$0.460Fits in one request

Gemini 3.8 Flash 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 Gemini 3.8 Flash and Grok 4.5
SpecificationGoogle Gemini 3.8 FlashSpaceXAI Grok 4.5
MakerGooglexAI
WeightsNo public weights listedNo public weights listed
ReleasedSeptember 2, 2026July 8, 2026
Context window1.05M500K
Input $/Mtok$0.75$2.00
Output $/Mtok$3.75$6.00
Coding index61.658.6
Independent measurements behind it66
Cost per solved task$2.74$0.62
SourceOpenRouter listingOpenRouter listing

Questions

Is Gemini 3.8 Flash better than Grok 4.5 for coding?

Pick Gemini 3.8 Flash for coding: it scores 61.6 on the Vibe Coding Index against 58.6 for Grok 4.5. Pick Grok 4.5 for a lower cost per solved task ($0.62 against $2.74) and work measured by LiveBench coding or SWE-bench Verified (Vals AI), where it leads.

Which is cheaper, Gemini 3.8 Flash or Grok 4.5?

Gemini 3.8 Flash costs $0.75 per million input tokens and $3.75 per million output tokens; Grok 4.5 costs $2.00 and $6.00. Per solved SWE-bench Verified task, Gemini 3.8 Flash costs $2.74 and Grok 4.5 $0.62.

Which has the bigger context window, Gemini 3.8 Flash or Grok 4.5?

Gemini 3.8 Flash, with 1.05M tokens against 500K.

How many benchmarks is the Gemini 3.8 Flash vs Grok 4.5 comparison based on?

114 benchmarks have a result for both models as of October 21, 2026. Gemini 3.8 Flash's coding index rests on 6 independent benchmarks and Grok 4.5's on 6. Where only one model has a result, the page says so instead of naming a winner.

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<p style="font:13px/1.4 sans-serif;margin:6px 0 0">Source: <a href="https://llmbenchmark.ai/compare/gemini-3-8-flash-vs-grok-4-5">LLMBenchmark.ai, Gemini 3.8 Flash vs Grok 4.5</a></p>