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Head-to-head comparison

Claude Sonnet 5 vs o3

Claude Sonnet 5 (Anthropic) and o3 (OpenAI) compared on the ModelCap Index, API price, context window, provider availability, weight access and every public benchmark board they share. Figures are the same ones shown on the live rankings; nothing here is a hidden score.

Snapshot as of 18 August 2026

As of 18 August 2026, Claude Sonnet 5 holds the stronger ModelCap Index position (#13 vs #37); o3 is 1.3× cheaper per output token ($8.00/1M vs $10.00/1M); and Claude Sonnet 5 offers the longer context window (1M vs 200K tokens).

Which should you choose?

Choose Claude Sonnet 5 if…

  • you want the stronger overall ModelCap Index position — #13 against #37 (73.6 vs 55.1 points).
  • you need the longer context window — 1M tokens against 200K.
  • you want provider choice — 5 listed API providers against 1.
  • Arena coding is your yardstick — 1523 against 1460.
  • Artificial Analysis Intelligence Index is your yardstick — 55.3 against 31.1.
  • you want the more recently listed model — Claude Sonnet 5 was listed 30 June 2026, o3 16 April 2025.

Choose o3 if…

  • API cost matters — $8.00/1M output tokens against $10.00/1M, about 1.3× cheaper.

Claude Sonnet 5 vs o3: specs, pricing and context

Specification comparison of Claude Sonnet 5 and o3
FieldClaude Sonnet 5Anthropico3OpenAI
ModelCap Index position#13#37
Index score73.655.1
EvidenceMeasuredMeasured
Input price / 1M tokens$2.00$2.00
Output price / 1M tokens$10.00$8.00
Context window1M tokens200K tokens
Max output tokens128K100K
API providers listed51
Weight accessAPI onlyAPI only
Input modalitiesText, Image, FileImage, Text, File
First listed30 June 202616 April 2025
PublisherAnthropicOpenAI

Evidence: 4 public benchmark observations across 4 boards · 4 public benchmark observations across 4 boards. Prices are the lowest listed API offer per million tokens observed on the OpenRouter catalogue.

Benchmark scores: Claude Sonnet 5 vs o3

Public benchmark boards where Claude Sonnet 5 or o3 has a published result
BoardClaude Sonnet 5o3Leads
Arena codingArena (LMArena)15231514–1531High14601453–1466Claude Sonnet 5
LMArena AgentLMArena7.1%4.9%–9.4%High—Only one result
ARC-AGI-2ARC Prize Foundation—6.5%HighOnly one result
SWE-benchSWE-bench (Princeton / SWE-agent team)—58.4%Only one result
BFCL V4UC Berkeley (Gorilla)—63.1PromptOnly one result
Artificial Analysis Intelligence IndexArtificial Analysis55.3intelligence-index31.1intelligence-indexClaude Sonnet 5

Scores are the sources' own published figures for each model's best evaluated configuration; ModelCap never re-runs a benchmark.

Want a different pairing? Open the interactive comparison tool to swap either model for any current ranked language model.

Claude Sonnet 5 vs o3: common questions

Is Claude Sonnet 5 better than o3?

Claude Sonnet 5 ranks higher on the ModelCap Index as of 18 August 2026: #13 against #37. That is a capability ranking built from public benchmark evidence with published uncertainty; whether it is "better" for you also depends on price, context and where you can run it.

Is Claude Sonnet 5 cheaper than o3?

o3 is cheaper on output tokens: $8.00/1M against $10.00/1M. Input tokens are $2.00/1M for Claude Sonnet 5 and $2.00/1M for o3. Prices are the lowest listed API offer ModelCap observed, in USD per million tokens.

Which has the bigger context window, Claude Sonnet 5 or o3?

Claude Sonnet 5 has the larger context window: 1M tokens against 200K.

Which is better for coding, Claude Sonnet 5 or o3?

Arena coding: Claude Sonnet 5 1523, o3 1460 — Claude Sonnet 5 leads.

Are Claude Sonnet 5 and o3 open-weight models?

Claude Sonnet 5: API only. o3: API only. Open weights mean the checkpoint can be downloaded and self-hosted under its licence; API-only models are available solely through hosted endpoints.

Where can I run Claude Sonnet 5 and o3?

ModelCap currently lists 5 API providers for Claude Sonnet 5 and 1 for o3, from the OpenRouter catalogue snapshot the site serves; each model page lists the providers and their prices.

How current is this Claude Sonnet 5 vs o3 comparison?

Every figure comes from the sealed ModelCap dataset published 18 August 2026; the page re-renders within a minute of each data refresh, and the ModelCap Index positions are the same ones shown on the live rankings.

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