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Comparison · 2 models · Updated Oct 4, 2026

o3 vs Claude Sonnet 4.5

Too close to call on our weighted score (o3 58, Claude Sonnet 4.5 55). The right pick depends on what you value most.

  1. OpenAI

    o3

    Released Apr 16, 2025

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

  2. Anthropic

    Claude Sonnet 4.5

    Released Sep 29, 2025

    55/100
    • ECI146.8
    • Price$3.00 / $15.00
    • Context200K
    Full specs Remove Claude Sonnet 4.5

  3. Add a model

    Make it a three-way comparison.

01 — Verdict

Too close to call

It is close. Our weighted score puts them within 3 points (o3 58/100, Claude Sonnet 4.5 55/100), so choose by what matters most for your work: o3 for raw capability. The score weighs capability 50%, price 25%, inputs & features 15%, context window 10%.

  • Capabilityo3Capabilities Index (ECI): o3 146.9 · Claude Sonnet 4.5 146.8
  • Lowest priceo3o3 $3.50 · Claude Sonnet 4.5 $6.00 per 1M tokens (3:1 blend)
  • Longest contextAbout the sameo3 200,000 · Claude Sonnet 4.5 200,000 tokens
  • Widest inputsSame inputso3: Text, Images, PDFs · Claude Sonnet 4.5: Text, Images, PDFs
  • Self-hostingNo open weightsBoth are available only through APIs
How the score is built
MeasureWeighto3Claude Sonnet 4.5
CapabilityCapabilities Index (ECI)50%7474
Price25%2413
Inputs & features15%8080
Context window10%3232
Overall100%58/10055/100
02 — Side by side

Every spec in one table

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

o3 vs Claude Sonnet 4.5 specifications side by side
Specificationo3OpenAIClaude Sonnet 4.5Anthropic
Capability
Capabilities Index (ECI)146.9 (best)146.8
ECI rank#63 of 148 (best)#64 of 148
GPQA DiamondGraduate-level science questions81.8%82.3% (best)
FrontierMath Tiers 1–3Research-level mathematics33.3% (best)23.9%
OTIS Mock AIME 2024–2025Competition mathematics84.4% (best)77.8%
SWE-bench VerifiedFixing real GitHub issues62.3%71.3% (best)
SimpleQA VerifiedShort factual questions49.4% (best)30.7%
Price per million tokens
Input$2.00 (best)$3.00
Output$8.00 (best)$15.00
Cached input$0.50$0.30 (best)
Blended (3:1)$3.50 (best)$6.00
Long-context rateSame rateSame rate
Price sourceOfficial OpenAI APIOfficial Anthropic API
Limits
Context window200,000 tokens200,000 tokens
Max output100,000 tokens (best)64,000 tokens
Inputs and features
TextYesYes
ImagesYesYes
PDFsYesYes
AudioNoNo
VideoNoNo
ReasoningYeslow · medium · highYes
Tool callingYesYes
Structured outputYesYes
Availability
WeightsProprietaryProprietary
API model IDo3claude-sonnet-4-5
API providers1828 (best)
ReleasedApr 16, 2025Sep 29, 2025
Knowledge cutoffMay 2024Jul 31, 2025
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.

  • o3$36.00
  • Claude Sonnet 4.5$60.00
04 — Questions

Which should you choose?

Which is better: o3 or Claude Sonnet 4.5?

It is close. Our weighted score puts them within 3 points (o3 58/100, Claude Sonnet 4.5 55/100), so choose by what matters most for your work: o3 for raw capability. The score weighs capability 50%, price 25%, inputs & features 15%, context window 10%.

Which is cheaper, o3 or Claude Sonnet 4.5?

o3 is cheaper at $2.00 input / $8.00 output per million tokens (official OpenAI API price). Claude Sonnet 4.5 costs $3.00 input / $15.00 output per million tokens (official Anthropic API price). At a typical mix of three input tokens to one output token, that is $3.50 per million tokens for o3 versus $6.00 for Claude Sonnet 4.5 (1.7× as much).

Which scores higher on benchmarks?

o3 scores higher on the Capabilities Index (ECI): o3 146.9 (#63 of 148) and Claude Sonnet 4.5 146.8 (#64 of 148). The confidence ranges of the top two overlap (144.9–148.6 vs 145.3–148.5), so treat the gap as small. On individual benchmarks: GPQA Diamond — Claude Sonnet 4.5 82.3%, o3 81.8%; FrontierMath Tiers 1–3 — o3 33.3%, Claude Sonnet 4.5 23.9%; OTIS Mock AIME 2024–2025 — o3 84.4%, Claude Sonnet 4.5 77.8%; SWE-bench Verified — Claude Sonnet 4.5 71.3%, o3 62.3%; SimpleQA Verified — o3 49.4%, Claude Sonnet 4.5 30.7%.

Which is better for coding?

Claude Sonnet 4.5 resolves more real GitHub issues on SWE-bench Verified: Claude Sonnet 4.5 71.3% and o3 62.3%. Both support tool calling for agent workflows.

Which has the bigger context window?

o3 and Claude Sonnet 4.5 share the same 200,000-token context window. Maximum output per response: o3 up to 100,000, Claude Sonnet 4.5 up to 64,000 tokens.

Which can read images, PDFs, audio or video?

o3 accepts text, images and PDFs; Claude Sonnet 4.5 accepts text, images and PDFs. They handle the same number of input types.

Are any of these open source?

No. o3 and Claude Sonnet 4.5 are proprietary and only available through APIs and apps.

Which is newer?

Claude Sonnet 4.5 is the newest, released Sep 29, 2025. o3 came out Apr 16, 2025. Knowledge cutoff: o3 May 2024, Claude Sonnet 4.5 Jul 31, 2025.

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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