Model comparison

Mistral Medium 3.5 vs o3

o3 is the stronger model overall, scoring 47.5 to 40.2 on the Noometry Index.

Last verified October 12, 2026. 19 shared benchmarks.

Mistral Medium 3.5

Mistral AI

40.2

Rank #152 Confirmed

o3 OpenAI

47.5

Rank #61 Confirmed

Summary

They share 19 benchmarks with published results for both. Mistral Medium 3.5 scores higher in 2 categories and o3 in 7 categories; 8 gaps are clear of the uncertainty.
The widest gap is in reasoning, where o3 leads 32.0 to 17.3.
The biggest single-benchmark swing is Kagi LLM Benchmark: 41.4% for Mistral Medium 3.5 and 67.6% for o3.
Mistral Medium 3.5 is cheaper at $1.50 / $7.50 per million input/output tokens, against $2 / $8 for o3.
Mistral Medium 3.5 accepts more context: 262K tokens versus 200K.
Mistral Medium 3.5 has downloadable open weights; the other is API-only.

Side by side

Mistral Medium 3.5 and o3 specifications
	Mistral Medium 3.5	o3
Provider	Mistral AI	OpenAI
Noometry Index	40.2	47.5
Released	—	2025-04-16
Weights	Open	Proprietary
Context window	262K	200K
Max output	210K	100K
Input $ / M tokens	$1.50	$2
Output $ / M tokens	$7.50	$8
Results tracked	22	63

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Category by category

Coding o3 leads

Mistral Medium 3.5: 36.0 (#213), o3: 46.8 (#64)

Coding benchmarks
Benchmark	Mistral Medium 3.5	o3
LMArena Coding	1461	1408
SWE-bench Verified	—	62.3%
SWE-bench Verified (bash only)	—	58.4%
Aider Polyglot	—	81.3%
LMArena WebDev	1264	—
GSO	—	8.8%
WeirdML	—	52.4%
CadEval	—	74%
ALE-Bench	—	933.55

Agentic & Tool Use Not comparable

Mistral Medium 3.5: —, o3: 34.5 (#44)

Agentic & Tool Use benchmarks
Benchmark	Mistral Medium 3.5	o3
Berkeley Function Calling Leaderboard	—	63%
GDPval	—	30.8%
DeepResearch Bench	—	45.2%
OSWorld	—	23%
LMArena Search	—	1144
METR Time Horizons	—	65.4%

Reasoning o3 leads

Mistral Medium 3.5: 17.3 (#295), o3: 32.0 (#78)

Reasoning benchmarks
Benchmark	Mistral Medium 3.5	o3
Kagi LLM Benchmark	41.4%	67.6%
LMArena Hard Prompts	1436	1402
Epoch Capabilities Index	141.35	146.86
ARC-AGI-2	—	6.5%
SimpleBench	—	53.1%
NYT Connections (extended)	12.9%	—
ARC-AGI-1	—	60.8%
CritPt	—	1.4%
Chess Puzzles	—	38%
EnigmaEval	—	13.1%
Mystery Game Puzzles	—	29%
DTBench	—	84.8%
LMCA	—	39.7%
ForecastBench	—	62.5

Math o3 leads

Mistral Medium 3.5: 39.1 (#113), o3: 50.2 (#58)

Math benchmarks
Benchmark	Mistral Medium 3.5	o3
LMArena Math	1431	1426
FrontierMath (Tiers 1-3)	—	33.3%
OTIS Mock AIME 2024-2025	—	84.4%
Omni-MATH	—	71.4%
MATH Level 5	—	97.8%
FrontierMath (Feb 2025 set)	—	18.7%
FrontierMath Tier 4 (v1)	—	2.1%

Knowledge o3 leads

Mistral Medium 3.5: 40.0 (#126), o3: 54.6 (#52)

Knowledge benchmarks
Benchmark	Mistral Medium 3.5	o3
LMArena Expert	1432	1402
GPQA Diamond	—	81.8%
Humanity's Last Exam	—	20.3%
SimpleQA Verified	—	49.4%
MMLU-Pro	—	85.9%
Confabulations	—	14.4%
GPQA (HELM)	—	75.3%

Multimodal o3 leads

Mistral Medium 3.5: 38.3 (#65), o3: 41.4 (#36)

Multimodal benchmarks
Benchmark	Mistral Medium 3.5	o3
LMArena Vision	1223	1214
GeoBench	—	74%
VPCT	—	52%

Multilingual Too close to call

Mistral Medium 3.5: 51.9 (#100), o3: 51.7 (#105)

Multilingual benchmarks
Benchmark	Mistral Medium 3.5	o3
LMArena Non-English	1404	1401
LMArena Chinese	1442	1437
LMArena French	1448	1430
LMArena German	1451	1420
LMArena Korean	1385	1370
LMArena Russian	1395	1406
LMArena Spanish	1409	1395
LMArena Japanese	—	1403

Instruction Following Mistral Medium 3.5 leads

Mistral Medium 3.5: 74.6 (#90), o3: 72.8 (#127)

Instruction Following benchmarks
Benchmark	Mistral Medium 3.5	o3
LMArena Instruction Following	1415	1368
IFEval	—	86.9%

Long Context o3 leads

Mistral Medium 3.5: 43.2 (#103), o3: 53.3 (#6)

Long Context benchmarks
Benchmark	Mistral Medium 3.5	o3
LMArena Longer Query	1415	1372
Fiction.LiveBench	—	88.9%
CL-bench	—	17.8%

Writing & Preference o3 leads

Mistral Medium 3.5: 58.5 (#117), o3: 63.5 (#64)

Writing & Preference benchmarks
Benchmark	Mistral Medium 3.5	o3
LMArena Text	1421	1410
LMArena Creative Writing	1374	1359
LMArena Multi-Turn	1423	1405
Short-Story Creative Writing	—	83.9%
EQ-Bench Creative Writing	—	1676
WildBench	—	86.1%
EQ-Bench 4	993	—

Frequently asked questions

Is Mistral Medium 3.5 better than o3?

o3 is the stronger model overall, scoring 47.5 to 40.2 on the Noometry Index.

Which is cheaper, Mistral Medium 3.5 or o3?

Mistral Medium 3.5 is cheaper. It lists at $1.50 per million input tokens and $7.50 per million output tokens; o3 lists at $2 and $8.

Is Mistral Medium 3.5 or o3 better for coding?

o3 scores higher on coding benchmarks: 46.8 versus 36.0 in the Noometry coding category.

Which has the bigger context window?

Mistral Medium 3.5 does, with 262K tokens against 200K.

How many benchmarks do Mistral Medium 3.5 and o3 share?

19 benchmarks have published results for both models. Mistral Medium 3.5 has 22 scored results on Noometry and o3 has 63.