ZMIME
Comparison · 3 models · Updated Oct 4, 2026

Claude Sonnet 4.5 vs GPT-5.2 vs o3

Too close to call on our weighted score (GPT-5.2 61, o3 58, Claude Sonnet 4.5 55). The right pick depends on what you value most.

  1. 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

  2. OpenAI

    GPT-5.2

    Released Dec 11, 2025

    61/100
    • ECI153.5
    • Price$1.75 / $14.00
    • Context400K
    Full specs Remove GPT-5.2

  3. OpenAI

    o3

    Released Apr 16, 2025

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

Too close to call

It is close. Our weighted score puts them within 2 points (GPT-5.2 61/100, o3 58/100, Claude Sonnet 4.5 55/100), so choose by what matters most for your work: GPT-5.2 for raw capability and o3 on price. The score weighs capability 50%, price 25%, inputs & features 15%, context window 10%.

  • CapabilityGPT-5.2Capabilities Index (ECI): GPT-5.2 153.5 · o3 146.9 · Claude Sonnet 4.5 146.8
  • Lowest priceo3o3 $3.50 · GPT-5.2 $4.81 · Claude Sonnet 4.5 $6.00 per 1M tokens (3:1 blend)
  • Longest contextGPT-5.2GPT-5.2 400,000 · Claude Sonnet 4.5 200,000 · o3 200,000 tokens
  • Widest inputsClaude Sonnet 4.5 and o3Claude Sonnet 4.5: Text, Images, PDFs · GPT-5.2: Text, Images · o3: Text, Images, PDFs
  • Self-hostingNo open weightsAll three are available only through APIs
How the score is built
MeasureWeightClaude Sonnet 4.5GPT-5.2o3
CapabilityCapabilities Index (ECI)50%748374
Price25%131824
Inputs & features15%807080
Context window10%324432
Overall100%55/10061/10058/100
02 — Side by side

Every spec in one table

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

Claude Sonnet 4.5 vs GPT-5.2 vs o3 specifications side by side
SpecificationClaude Sonnet 4.5AnthropicGPT-5.2OpenAIo3OpenAI
Capability
Capabilities Index (ECI)146.8153.5 (best)146.9
ECI rank#64 of 148#38 of 148 (best)#63 of 148
GPQA DiamondGraduate-level science questions82.3%91.4% (best)81.8%
FrontierMath Tiers 1–3Research-level mathematics23.9%67.4% (best)33.3%
OTIS Mock AIME 2024–2025Competition mathematics77.8%96.1% (best)84.4%
SWE-bench VerifiedFixing real GitHub issues71.3%73.8% (best)62.3%
SimpleQA VerifiedShort factual questions30.7%37.1%49.4% (best)
Price per million tokens
Input$3.00$1.75 (best)$2.00
Output$15.00$14.00$8.00 (best)
Cached input$0.30$0.175 (best)$0.50
Blended (3:1)$6.00$4.81$3.50 (best)
Long-context rateSame rateSame rateSame rate
Price sourceOfficial Anthropic APIOfficial OpenAI APIOfficial OpenAI API
Limits
Context window200,000 tokens400,000 tokens (best)200,000 tokens
Max output64,000 tokens128,000 tokens (best)100,000 tokens
Inputs and features
TextYesYesYes
ImagesYesYesYes
PDFsYesNoYes
AudioNoNoNo
VideoNoNoNo
ReasoningYesYeslow · medium · high · xhighYeslow · medium · high
Tool callingYesYesYes
Structured outputYesYesYes
Availability
WeightsProprietaryProprietaryProprietary
API model IDclaude-sonnet-4-5gpt-5.2o3
API providers28 (best)2118
ReleasedSep 29, 2025Dec 11, 2025Apr 16, 2025
Knowledge cutoffJul 31, 2025Aug 31, 2025May 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.

  • Claude Sonnet 4.5$60.00
  • GPT-5.2$45.50
  • o3$36.00
04 — Questions

Which should you choose?

Which is better: Claude Sonnet 4.5, GPT-5.2 or o3?

It is close. Our weighted score puts them within 2 points (GPT-5.2 61/100, o3 58/100, Claude Sonnet 4.5 55/100), so choose by what matters most for your work: GPT-5.2 for raw capability and o3 on price. The score weighs capability 50%, price 25%, inputs & features 15%, context window 10%.

Which is cheaper, Claude Sonnet 4.5, GPT-5.2 or o3?

o3 is cheaper at $2.00 input / $8.00 output per million tokens (official OpenAI API price). GPT-5.2 costs $1.75 input / $14.00 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 $4.81 for GPT-5.2 (1.4× as much) and $6.00 for Claude Sonnet 4.5 (1.7× as much).

Which scores higher on benchmarks?

GPT-5.2 scores higher on the Capabilities Index (ECI): GPT-5.2 153.5 (#38 of 148), o3 146.9 (#63 of 148) and Claude Sonnet 4.5 146.8 (#64 of 148). Their confidence ranges do not overlap (151.7–155.4 vs 144.9–148.6), so the gap is a real one. On individual benchmarks: GPQA Diamond — GPT-5.2 91.4%, Claude Sonnet 4.5 82.3%, o3 81.8%; FrontierMath Tiers 1–3 — GPT-5.2 67.4%, o3 33.3%, Claude Sonnet 4.5 23.9%; OTIS Mock AIME 2024–2025 — GPT-5.2 96.1%, o3 84.4%, Claude Sonnet 4.5 77.8%; SWE-bench Verified — GPT-5.2 73.8%, Claude Sonnet 4.5 71.3%, o3 62.3%; SimpleQA Verified — o3 49.4%, GPT-5.2 37.1%, Claude Sonnet 4.5 30.7%.

Which is better for coding?

GPT-5.2 resolves more real GitHub issues on SWE-bench Verified: GPT-5.2 73.8%, Claude Sonnet 4.5 71.3% and o3 62.3%. All three support tool calling for agent workflows.

Which has the bigger context window?

GPT-5.2 has the largest context window at 400,000 tokens, against 200,000 for Claude Sonnet 4.5 and 200,000 for o3. Maximum output per response: Claude Sonnet 4.5 up to 64,000, GPT-5.2 up to 128,000, o3 up to 100,000 tokens.

Which can read images, PDFs, audio or video?

Claude Sonnet 4.5 accepts text, images and PDFs; GPT-5.2 accepts text and images; o3 accepts text, images and PDFs. Claude Sonnet 4.5 handles the widest range of inputs.

Are any of these open source?

No. Claude Sonnet 4.5, GPT-5.2 and o3 are proprietary and only available through APIs and apps.

Which is newer?

GPT-5.2 is the newest, released Dec 11, 2025. Claude Sonnet 4.5 came out Sep 29, 2025; o3 came out Apr 16, 2025. Knowledge cutoff: Claude Sonnet 4.5 Jul 31, 2025, GPT-5.2 Aug 31, 2025, 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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