Claude Sonnet 4.5 vs o3-pro
Comparing Claude Sonnet 4.5 and o3-pro across benchmarks, pricing, and capabilities.
Anthropic · OpenAI · Updated for 2026
Which is better?
Claude Sonnet 4.5 and o3-pro trade strengths across price, capabilities, and technical limits. The better choice depends on the workload.
On price, Claude Sonnet 4.5 is roughly 5.8x cheaper per token on a blended 3:1 input/output basis, which adds up quickly at production volume.
Based on current benchmark, pricing, and model metadata for 2026.
Choose Claude Sonnet 4.5
- cost matters — it's about 5.8x cheaper per token
- you want the most recent training data — it shipped Sep 2025
Choose o3-pro
- you want predictable pricing at $20.00/M input and $80.00/M output
At a glance
The differences that matter most.
Performance Benchmarks
Comparative analysis across standard metrics
Claude Sonnet 4.5 and o3-prodon't have any common benchmark datasets to compare. They may have been evaluated on different testing suites.
Arena Performance
Playground indexes and blind preference scores
Pricing Analysis
Price comparison per million tokens
For input processing, Claude Sonnet 4.5 ($3.00/1M tokens) is 6.7x cheaper than o3-pro ($20.00/1M tokens).
For output processing, Claude Sonnet 4.5 ($15.00/1M tokens) is 5.3x cheaper than o3-pro ($80.00/1M tokens).
In conclusion, o3-pro is more expensive than Claude Sonnet 4.5.*
* Using a 3:1 ratio of input to output tokens
Context Window
Maximum input and output token capacity
Both models have the same input context window of 200,000 tokens. o3-pro can generate longer responses up to 100,000 tokens, while Claude Sonnet 4.5 is limited to 64,000 tokens.
Input Capabilities
Supported data types and modalities
Both Claude Sonnet 4.5 and o3-pro support multimodal inputs.
They are both capable of processing various types of data, offering versatility in application.
Claude Sonnet 4.5
o3-pro
License
Usage and distribution terms
Both models are licensed under proprietary licenses.
Both models have usage restrictions defined by their respective organizations.
Proprietary
Closed source
Proprietary
Closed source
Release Timeline
When each model was launched
Claude Sonnet 4.5 was released on 2025-09-29, while o3-pro was released on 2025-06-10.
Claude Sonnet 4.5 is 4 months newer than o3-pro.
Sep 29, 2025
11 months ago
3mo newerJun 10, 2025
1.2 years ago
Knowledge Cutoff
When training data ends
Claude Sonnet 4.5 has a knowledge cutoff of 2025-01-31, while o3-pro has a cutoff of 2024-05-31.
Claude Sonnet 4.5 has more recent training data (up to 2025-01-31), making it potentially better informed about events through that date compared to o3-pro (2024-05-31).
Jan 2025
8 mo newerMay 2024
Provider Availability
Claude Sonnet 4.5 is available from Anthropic. o3-pro is available from OpenAI.
Claude Sonnet 4.5
o3-pro
Outputs Comparison
Judge for yourself.
Run your own prompts against Claude Sonnet 4.5 and o3-pro side-by-side, then vote on the output you prefer.
FAQ
Common questions about Claude Sonnet 4.5 vs o3-pro.