ZMIME
Comparison · 2 models · Updated Oct 4, 2026

Mistral Medium 3.5 vs o3

o3 comes out ahead, 58 to 55 on our weighted score, though Mistral Medium 3.5 is 14% cheaper per token.

  1. Mistral AI

    Mistral Medium 3.5

    Released Apr 29, 2026

    55/100
    • ECI141.4
    • Price$1.50 / $7.50
    • Context262K
    Full specs Remove Mistral Medium 3.5
  2. Our pick

    OpenAI

    o3

    Released Apr 16, 2025

    58/100
    • ECI146.9
    • Price$2.00 / $8.00
    • Context200K
    Full specs Remove o3

  3. Add a model

    Make it a three-way comparison.

01 — Verdict

o3 is our pick

o3 is the better all-round choice, scoring 58/100 against Mistral Medium 3.5 (55). It leads on capability and inputs & features. Mistral Medium 3.5 wins on price and context window. The score weighs capability 50%, price 25%, inputs & features 15%, context window 10%.

  • Capabilityo3Capabilities Index (ECI): o3 146.9 · Mistral Medium 3.5 141.4
  • Lowest priceMistral Medium 3.5Mistral Medium 3.5 $3.00 · o3 $3.50 per 1M tokens (3:1 blend)
  • Longest contextMistral Medium 3.5Mistral Medium 3.5 262,144 · o3 200,000 tokens
  • Widest inputso3Mistral Medium 3.5: Text, Images · o3: Text, Images, PDFs
  • Self-hostingMistral Medium 3.5Publishes downloadable weights
How the score is built
MeasureWeightMistral Medium 3.5o3
CapabilityCapabilities Index (ECI)50%6774
Price25%2724
Inputs & features15%7080
Context window10%3732
Overall100%55/10058/100
02 — Side by side

Every spec in one table

Highlighted cells lead their row. Dashes mean the data is not published.

Mistral Medium 3.5 vs o3 specifications side by side
SpecificationMistral Medium 3.5Mistral AIo3OpenAI
Capability
Capabilities Index (ECI)141.4146.9 (best)
ECI rank#95 of 148#63 of 148 (best)
GPQA DiamondGraduate-level science questions—81.8%
FrontierMath Tiers 1–3Research-level mathematics—33.3%
OTIS Mock AIME 2024–2025Competition mathematics—84.4%
SWE-bench VerifiedFixing real GitHub issues—62.3%
SimpleQA VerifiedShort factual questions—49.4%
Price per million tokens
Input$1.50 (best)$2.00
Output$7.50 (best)$8.00
Cached input$0.15 (best)$0.50
Blended (3:1)$3.00 (best)$3.50
Long-context rateSame rateSame rate
Price sourceOfficial Mistral APIOfficial OpenAI API
Limits
Context window262,144 tokens (best)200,000 tokens
Max output262,144 tokens (best)100,000 tokens
Inputs and features
TextYesYes
ImagesYesYes
PDFsNoYes
AudioNoNo
VideoNoNo
ReasoningYeshighYeslow · medium · high
Tool callingYesYes
Structured outputYesYes
Availability
WeightsOpenProprietary
API model IDmistral-medium-2604o3
API providers1218 (best)
ReleasedApr 29, 2026Apr 16, 2025
Knowledge cutoff—May 2024
03 — Cost

What would a month cost?

Enter your expected volume in millions of tokens. List prices only; caching and batch discounts would lower these.

  • Mistral Medium 3.5$30.00
  • o3$36.00
04 — Questions

Which should you choose?

Which is better: Mistral Medium 3.5 or o3?

o3 is the better all-round choice, scoring 58/100 against Mistral Medium 3.5 (55). It leads on capability and inputs & features. Mistral Medium 3.5 wins on price and context window. The score weighs capability 50%, price 25%, inputs & features 15%, context window 10%.

Which is cheaper, Mistral Medium 3.5 or o3?

Mistral Medium 3.5 is cheaper at $1.50 input / $7.50 output per million tokens (official Mistral API price). o3 costs $2.00 input / $8.00 output per million tokens (official OpenAI API price). At a typical mix of three input tokens to one output token, that is $3.00 per million tokens for Mistral Medium 3.5 versus $3.50 for o3 (1.2× as much).

Which scores higher on benchmarks?

o3 scores higher on the Capabilities Index (ECI): o3 146.9 (#63 of 148) and Mistral Medium 3.5 141.4 (#95 of 148). Their confidence ranges do not overlap (144.9–148.6 vs 138.4–143.7), so the gap is a real one.

Which is better for coding?

There are no published SWE-bench Verified results for Mistral Medium 3.5 yet, so there is no like-for-like coding score. On overall capability, o3 leads, which tends to carry over to coding, but test on your own codebase. Both support tool calling for agent workflows.

Which has the bigger context window?

Mistral Medium 3.5 has the largest context window at 262,144 tokens, against 200,000 for o3. Maximum output per response: Mistral Medium 3.5 up to 262,144, o3 up to 100,000 tokens.

Which can read images, PDFs, audio or video?

Mistral Medium 3.5 accepts text and images; o3 accepts text, images and PDFs. o3 handles the widest range of inputs.

Are any of these open source?

Mistral Medium 3.5 publishes its weights and can be self-hosted; o3 is proprietary.

Which is newer?

Mistral Medium 3.5 is the newest, released Apr 29, 2026. o3 came out Apr 16, 2025. Knowledge cutoff: o3 May 2024.

How do you decide the winner?

Each model gets a 0–100 score on capability (50%, independent benchmark results); price (25%, blended price per million tokens (3 input : 1 output), log scale); inputs & features (15%, image, PDF, audio and video input, tool calling, structured output and reasoning); context window (10%, maximum tokens per request, log scale). Dimensions missing for any model are dropped and the remaining weights rescaled, so every model is judged on the same evidence. Specs and prices come from public model listings and the labs’ own API pages; capability scores come from independent benchmark runs. Data updated Oct 4, 2026.

05 — Keep comparing

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