Gemini 3.8 Flash vs o3

Updated October 21, 2026. 68 benchmarks have a result for both. Coding is ranked on the Vibe Coding Index; every other board is shown as published.

Replace Gemini 3.8 Flash Replace o3

Gemini 3.8 FlashGoogle

Coding: 70.5
Overall: 40.9
Output $/M: $4.125

o3OpenAI

Coding: 70.7
Overall: 20.2
Output $/M: $8.00

vs boards won of 68 shared

Decision reading

Gemini 3.8 Flash and o3 are level for coding, 70.5 against 70.7 on the Vibe Coding Index, so price and context decide.

Pick Gemini 3.8 Flash when output tokens cost 1.9x less, or when the context window is larger, 1.05M against 200K tokens. Pick o3 when a solved task costs $0.571 against $2.74, or when what matters is TaxEval (Vals AI) or MortgageTax (Vals AI), where it leads.

Model AGemini 3.8 FlashGoogle70.5/1002 independent benchmarks$2.74 per solved task Model Bo3OpenAI70.7/1002 independent benchmarks$0.571 per solved task

685829

Shared results: 68
Gemini 3.8 Flash only: 58
o3 only: 29
Like-for-like categories: 7 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.

Coding
Vibe Coding Index, four public coding benchmarks
No call
Level: 70.5 against 70.7, inside 2 points.
2 benchmarks behind each score
Intelligence
AA Intelligence Index
Gemini 3.8 Flash
Gemini 3.8 Flash leads, 40.9 against 20.2.
Same board, both measured
Agentic work
AA Agentic Index
No call
Only Gemini 3.8 Flash has a AA Agentic Index result, 40.2.
Directional only
Reasoning
GPQA Diamond
Gemini 3.8 Flash
Gemini 3.8 Flash leads, 94.4% against 84.1%.
Same board, both measured
Math
AIME
No call
Only o3 has a AIME result, 85.3%.
Directional only
Knowledge
MMLU Pro
Gemini 3.8 Flash
Gemini 3.8 Flash leads, 90.2% against 85.6%.
Same board, both measured
Web design
Design Arena: websites
Gemini 3.8 Flash
Gemini 3.8 Flash leads, 1301 against 1036.
Same board, both measured
General
Vals Index
No call
Only Gemini 3.8 Flash has a Vals Index result, 56.0%.
Directional only
Long documents
Listed context window
Gemini 3.8 Flash
Gemini 3.8 Flash takes 1.05M tokens against 200K.
Listed by OpenRouter
Everyday cost
1K input + 500 output tokens
Gemini 3.8 Flash
Gemini 3.8 Flash $0.0029, o3 $0.0060 per turn.
List prices
Cost per solved task
One SWE-bench Verified task, solved
o3
Gemini 3.8 Flash $2.74, o3 $0.571.
Published attempt cost and pass rate

At a glance

Coding index: Gemini 3.8 Flash 70.5 from 2 benchmarks, o3 70.7 from 2 benchmarks.
Widest category: Web design, 29.8 points apart on average over 5 shared benchmarks.
Widest single gap: ARC-AGI-2: Gemini 3.8 Flash 89.2% against o3 6.5%, 82.6 points apart on a 0 to 100 scale.
Output price: Gemini 3.8 Flash $4.125 against o3 $8.00 per million output tokens, 1.9x apart.
Context window: Gemini 3.8 Flash takes 1.05M tokens, o3 200K.

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
Category	Gemini 3.8 Flash	o3
Coding	5	0
Intelligence	2	0
Reasoning	14	0
Math	4	0
Knowledge	8	2
Web design	5	0
General	27	1
All shared boards	65	3

CodingLike-for-likeFour of these boards feed the Vibe Coding Index50

Coding benchmarks for Gemini 3.8 Flash and o3
Benchmark	Gemini 3.8 Flash	o3	Leader
Aider polyglot	Not measured	81.3%	Only o3 measured
SWE-bench Verified	Not measured	58.4%	Only o3 measured
SWE-bench Multimodal	Not measured	36.0%	Only o3 measured
LiveBench coding	82.2%	Not measured	Only Gemini 3.8 Flash measured
LMArena WebDev	1585	Not measured	Only Gemini 3.8 Flash measured
AA Coding Index	76.3	Not measured	Only Gemini 3.8 Flash measured
LiveCodeBench (Vals AI)	89.5%	83.9%	Gemini 3.8 Flash
SWE-bench Verified (Vals AI)	80.0%	Not measured	Only Gemini 3.8 Flash measured
Terminal-Bench 4 (Vals AI)	19.7%	Not measured	Only Gemini 3.8 Flash measured
Vibe Code Bench (Vals AI)	78.7%	Not measured	Only Gemini 3.8 Flash measured
Code migration (Vals AI)	36.5%	Not measured	Only Gemini 3.8 Flash measured
ProgramBench (Vals AI)	1.0%	Not measured	Only Gemini 3.8 Flash measured
IOI (Vals AI)	56.9%	Not measured	Only Gemini 3.8 Flash measured
Terminal-Bench 2.1 (Vals AI)	81.3%	Not measured	Only Gemini 3.8 Flash measured
SWE-bench Multimodal (Vals AI)	40.8%	Not measured	Only Gemini 3.8 Flash measured
Vibe Code Bench 1-100 (Vals AI)	18.8%	Not measured	Only Gemini 3.8 Flash measured
SkillsBench (Vals AI)	58.0%	Not measured	Only Gemini 3.8 Flash measured
CyberBench (Vals AI)	43.8%	Not measured	Only Gemini 3.8 Flash measured
LiveCodeBench (Artificial Analysis run)	Not measured	80.8%	Only o3 measured
SciCode	56.6%	Not measured	Only Gemini 3.8 Flash measured
Terminal-Bench Hard (Artificial Analysis run)	Not measured	37.1%	Only o3 measured
FrontierCode	41.2%	Not measured	Only Gemini 3.8 Flash measured
FrontierSWE	19.6%	Not measured	Only Gemini 3.8 Flash measured
GSO-Bench	Not measured	8.8%	Only o3 measured
WeirdML	84.8%	52.4%	Gemini 3.8 Flash
ALE-Bench	1269.7	933.5	Gemini 3.8 Flash
LMArena Text: coding	1508	1407	Gemini 3.8 Flash
LMArena Text: software and IT	1507	1415	Gemini 3.8 Flash
LMArena WebDev: React	1577	Not measured	Only Gemini 3.8 Flash measured
LMArena WebDev: HTML	1616	Not measured	Only Gemini 3.8 Flash measured
LMArena WebDev: from an image	1593	Not measured	Only Gemini 3.8 Flash measured
Neither model has a result on the other 7 boards here

IntelligenceLike-for-likePublic boards, shown as published, kept out of the index20

Intelligence benchmarks for Gemini 3.8 Flash and o3
Benchmark	Gemini 3.8 Flash	o3	Leader
AA Intelligence Index	40.9	20.2	Gemini 3.8 Flash
Epoch Capabilities Index	157.4	146.7	Gemini 3.8 Flash

Agentic workDirectional onlyPublic boards, shown as published, kept out of the index30 boards, none shared

Agentic work benchmarks for Gemini 3.8 Flash and o3
Benchmark	Gemini 3.8 Flash	o3	Leader
AA Agentic Index	40.2	Not measured	Only Gemini 3.8 Flash measured
Design Arena: agents building web apps	1238	Not measured	Only Gemini 3.8 Flash measured
Design Arena: agents building full-stack apps	1244	Not measured	Only Gemini 3.8 Flash measured
Design Arena: agents building mobile apps	1236	Not measured	Only Gemini 3.8 Flash measured
Design Arena: agents building Android apps	1078	Not measured	Only Gemini 3.8 Flash measured
Design Arena: agents building Godot games	1273	Not measured	Only Gemini 3.8 Flash measured
Design Arena: PowerPoint slides	1178	Not measured	Only Gemini 3.8 Flash measured
Design Arena: spreadsheets	1052	Not measured	Only Gemini 3.8 Flash measured
LiveBench research	79.1%	Not measured	Only Gemini 3.8 Flash measured
LiveBench browser	64.0%	Not measured	Only Gemini 3.8 Flash measured
LiveBench long agentic	30.1%	Not measured	Only Gemini 3.8 Flash measured
SREBench (Vals AI)	11.1%	Not measured	Only Gemini 3.8 Flash measured
Finance Agent (Vals AI)	61.4%	Not measured	Only Gemini 3.8 Flash measured
Tax Agent Bench (Vals AI)	32.1%	Not measured	Only Gemini 3.8 Flash measured
Legal Research Bench (Vals AI)	38.9%	Not measured	Only Gemini 3.8 Flash measured
Harvey's Legal Agent Benchmark (Vals AI)	12.1%	Not measured	Only Gemini 3.8 Flash measured
Excel Modeling Benchmark (Vals AI)	72.2%	Not measured	Only Gemini 3.8 Flash measured
BioMysteryBench (Vals AI)	62.2%	Not measured	Only Gemini 3.8 Flash measured
Terminal-Bench-Science (Vals AI)	8.6%	Not measured	Only Gemini 3.8 Flash measured
Vals Science Index	35.8%	Not measured	Only Gemini 3.8 Flash measured
Time Horizon Index (Vals AI)	18.8%	Not measured	Only Gemini 3.8 Flash measured
CUA-bench (Vals AI)	4.2%	Not measured	Only Gemini 3.8 Flash measured
τ²-Bench Telecom	Not measured	80.7%	Only o3 measured
APEX-Agents	64.3%	Not measured	Only Gemini 3.8 Flash measured
METR time horizons	Not measured	65.4%	Only o3 measured
Remote Labor Index	5.8%	Not measured	Only Gemini 3.8 Flash measured
GDPval	Not measured	30.8%	Only o3 measured
DeepResearch Bench	Not measured	45.2%	Only o3 measured
OSWorld	Not measured	23.0%	Only o3 measured
Vending-Bench 2	$5,094	Not measured	Only Gemini 3.8 Flash measured
Neither model has a result on the other 9 boards here

ReasoningLike-for-likePublic boards, shown as published, kept out of the index140

Reasoning benchmarks for Gemini 3.8 Flash and o3
Benchmark	Gemini 3.8 Flash	o3	Leader
GPQA Diamond	94.4%	84.1%	Gemini 3.8 Flash
LiveBench reasoning	89.3%	Not measured	Only Gemini 3.8 Flash measured
MysteryMechanism (Vals AI)	36.5%	Not measured	Only Gemini 3.8 Flash measured
MMMU Pro (Vals AI)	89.1%	80.4%	Gemini 3.8 Flash
GPQA Diamond (Artificial Analysis run)	95.3%	82.7%	Gemini 3.8 Flash
Humanity's Last Exam (Artificial Analysis run)	47.8%	20.1%	Gemini 3.8 Flash
GPQA Diamond (Epoch AI run)	95.4%	81.8%	Gemini 3.8 Flash
ARC-AGI	98.5%	60.8%	Gemini 3.8 Flash
ARC-AGI-2	89.2%	6.5%	Gemini 3.8 Flash
SimpleBench	Not measured	53.1%	Only o3 measured
Chess puzzles	58.0%	37.0%	Gemini 3.8 Flash
Mystery game puzzles	47.0%	29.0%	Gemini 3.8 Flash
VPCT	Not measured	52.0%	Only o3 measured
LMArena Text: hard prompts	1509	1402	Gemini 3.8 Flash
LMArena Text: expert	1526	1402	Gemini 3.8 Flash
LMArena Text: hard prompts in English	1504	1411	Gemini 3.8 Flash
LMArena Vision: diagrams	1345	1220	Gemini 3.8 Flash
LMArena Vision: homework	1351	1234	Gemini 3.8 Flash
Neither model has a result on the other 3 boards here

MathLike-for-likePublic boards, shown as published, kept out of the index40

Math benchmarks for Gemini 3.8 Flash and o3
Benchmark	Gemini 3.8 Flash	o3	Leader
AIME	Not measured	85.3%	Only o3 measured
MATH 500 (Vals AI)	Not measured	94.6%	Only o3 measured
MGSM (Vals AI)	Not measured	91.8%	Only o3 measured
AA Math Index	Not measured	88.3	Only o3 measured
AIME 2025 (Artificial Analysis run)	Not measured	88.3%	Only o3 measured
OTIS Mock AIME	98.9%	84.4%	Gemini 3.8 Flash
FrontierMath, tiers 1 to 3	68.4%	33.3%	Gemini 3.8 Flash
FrontierMath, tier 4	22.0%	Not measured	Only Gemini 3.8 Flash measured
ProofBench	48.0%	Not measured	Only Gemini 3.8 Flash measured
MATH level 5	Not measured	97.8%	Only o3 measured
LMArena Text: math	1532	1426	Gemini 3.8 Flash
LMArena Text: mathematical work	1519	1423	Gemini 3.8 Flash
Neither model has a result on the other 1 board here

KnowledgeLike-for-likePublic boards, shown as published, kept out of the index82

Knowledge benchmarks for Gemini 3.8 Flash and o3
Benchmark	Gemini 3.8 Flash	o3	Leader
MMLU Pro	90.2%	85.6%	Gemini 3.8 Flash
LegalBench (Vals AI)	87.0%	83.8%	Gemini 3.8 Flash
CorpFin (Vals AI)	Not measured	59.7%	Only o3 measured
TaxEval (Vals AI)	74.5%	74.6%	o3
MortgageTax (Vals AI)	65.3%	65.7%	o3
MedQA (Vals AI)	Not measured	96.1%	Only o3 measured
MedCode (Vals AI)	48.1%	47.3%	Gemini 3.8 Flash
MMLU Pro (Artificial Analysis run)	Not measured	85.3%	Only o3 measured
SimpleQA Verified	69.7%	49.4%	Gemini 3.8 Flash
GeoBench	Not measured	74.0%	Only o3 measured
LMArena Text: science	1523	1429	Gemini 3.8 Flash
LMArena Text: medicine and healthcare	1508	1448	Gemini 3.8 Flash
LMArena Text: legal and government	1497	1428	Gemini 3.8 Flash
LMArena Text: business and finance	1479	1393	Gemini 3.8 Flash
Neither model has a result on the other 3 boards here

Web designLike-for-likePublic boards, shown as published, kept out of the index50

Web design benchmarks for Gemini 3.8 Flash and o3
Benchmark	Gemini 3.8 Flash	o3	Leader
Design Arena: websites	1301	1036	Gemini 3.8 Flash
Design Arena: UI components	1318	1016	Gemini 3.8 Flash
Design Arena: game dev	1305	1034	Gemini 3.8 Flash
Design Arena: data viz	1269	1200	Gemini 3.8 Flash
Design Arena: 3D	1295	Not measured	Only Gemini 3.8 Flash measured
Design Arena: all code categories	1304	1021	Gemini 3.8 Flash
Design Arena: SVG	1295	Not measured	Only Gemini 3.8 Flash measured
Design Arena: ASCII art	1264	Not measured	Only Gemini 3.8 Flash measured
LiveBench design	72.7%	Not measured	Only Gemini 3.8 Flash measured

GeneralLike-for-likePublic boards, shown as published, kept out of the index271

General benchmarks for Gemini 3.8 Flash and o3
Benchmark	Gemini 3.8 Flash	o3	Leader
Vals Index	56.0%	Not measured	Only Gemini 3.8 Flash measured
LiveBench data analysis	54.0%	Not measured	Only Gemini 3.8 Flash measured
Public Benefits Bench (Vals AI)	65.3%	Not measured	Only Gemini 3.8 Flash measured
SAGE (Vals AI)	35.1%	41.8%	o3
MedScribe (Vals AI)	84.5%	76.7%	Gemini 3.8 Flash
IFBench	Not measured	71.4%	Only o3 measured
Long context reasoning (AA-LCR)	84.0%	74.7%	Gemini 3.8 Flash
DTBench	95.7%	84.8%	Gemini 3.8 Flash
LMCA	52.9%	39.7%	Gemini 3.8 Flash
Fiction.LiveBench	Not measured	88.9%	Only o3 measured
Creative writing (Lech Mazur)	Not measured	83.9%	Only o3 measured
CL-bench	Not measured	17.8%	Only o3 measured
Surface Evolver Bench	76.9%	Not measured	Only Gemini 3.8 Flash measured
Furniture assembly	31.7%	Not measured	Only Gemini 3.8 Flash measured
LMArena Text	1499	1410	Gemini 3.8 Flash
LMArena Text: instruction following	1492	1368	Gemini 3.8 Flash
LMArena Text: creative writing	1488	1359	Gemini 3.8 Flash
LMArena Vision	1315	1214	Gemini 3.8 Flash
LMArena Text: English	1498	1417	Gemini 3.8 Flash
LMArena Text: non-English	1491	1401	Gemini 3.8 Flash
LMArena Text: Chinese	1553	1437	Gemini 3.8 Flash
LMArena Text: German	1501	1420	Gemini 3.8 Flash
LMArena Text: Japanese	1507	1403	Gemini 3.8 Flash
LMArena Text: Korean	1464	1370	Gemini 3.8 Flash
LMArena Text: French	1496	1430	Gemini 3.8 Flash
LMArena Text: Spanish	1487	1395	Gemini 3.8 Flash
LMArena Text: Russian	1514	1406	Gemini 3.8 Flash
LMArena Text: Polish	1497	1438	Gemini 3.8 Flash
LMArena Text: multi-turn	1503	1405	Gemini 3.8 Flash
LMArena Text: longer queries	1507	1372	Gemini 3.8 Flash
LMArena Text: writing and language	1494	1372	Gemini 3.8 Flash
LMArena Text: entertainment and media	1480	1373	Gemini 3.8 Flash
LMArena Vision: English	1318	1221	Gemini 3.8 Flash
LMArena Vision: Chinese	1416	1237	Gemini 3.8 Flash
LMArena Vision: reading text	1333	1218	Gemini 3.8 Flash
LMArena Vision: humor	1321	1222	Gemini 3.8 Flash
LMArena Vision: captioning	Not measured	1210	Only o3 measured
LMArena Vision: recognizing things	Not measured	1234	Only o3 measured
LMArena Vision: creative writing	1299	1201	Gemini 3.8 Flash
Neither model has a result on the other 7 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 o3
Benchmark	Gemini 3.8 Flash	o3	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

Gemini 3.8 Flash$0.0029Fits in one request

o3$0.0060Fits in one request

Gemini 3.8 Flash costs less

Repository review

50K input + 3K output tokens

Gemini 3.8 Flash$0.054Fits in one request

o3$0.124Fits in one request

Gemini 3.8 Flash costs less

Agent loop

200K input + 10K output tokens

Gemini 3.8 Flash$0.206Fits in one request

o3$0.480Exceeds the context window

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 o3
Specification	Google Gemini 3.8 Flash	OpenAI o3
Maker	Google	OpenAI
Weights	No public weights listed	No public weights listed
Released	September 2, 2026	April 16, 2025
Context window	1.05M	200K
Input $/Mtok	$0.825	$2.00
Output $/Mtok	$4.125	$8.00
Coding index	70.5	70.7
Independent measurements behind it	2	2
Cost per solved task	$2.74	$0.571
Source	OpenRouter listing	OpenRouter listing

Questions

Is Gemini 3.8 Flash better than o3 for coding?

Gemini 3.8 Flash and o3 are level for coding, 70.5 against 70.7 on the Vibe Coding Index, so price and context decide. Pick Gemini 3.8 Flash when output tokens cost 1.9x less, or when the context window is larger, 1.05M against 200K tokens. Pick o3 when a solved task costs $0.571 against $2.74, or when what matters is TaxEval (Vals AI) or MortgageTax (Vals AI), where it leads.

Which is cheaper, Gemini 3.8 Flash or o3?

Gemini 3.8 Flash costs $0.825 per million input tokens and $4.125 per million output tokens; o3 costs $2.00 and $8.00. Per solved SWE-bench Verified task, Gemini 3.8 Flash costs $2.74 and o3 $0.571.

Which has the bigger context window, Gemini 3.8 Flash or o3?

Gemini 3.8 Flash, with 1.05M tokens against 200K.

How many benchmarks is the Gemini 3.8 Flash vs o3 comparison based on?

68 benchmarks have a result for both models as of October 21, 2026. Gemini 3.8 Flash's coding index rests on 2 independent benchmarks and o3's on 2. Where only one model has a result, the page says so instead of naming a winner.

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Decision reading

Which one for your work

Coding

Intelligence

Agentic work

Reasoning

Math

Knowledge

Web design

General

Long documents

Everyday cost

Cost per solved task

At a glance

Benchmark by benchmark

What each workload costs

Chat turn

Repository review

Agent loop

Specification differences

Questions

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