Claude Sonnet 4.5 vs o3
Claude Sonnet 4.5 and o3 are closely matched at 32.1 and 31.1 on the LLM Stats Score. o3 is 1.7x cheaper per token.
Anthropic · OpenAI · Updated for 2026
Which is better?
Claude Sonnet 4.5 and o3 are closely matched on the overall LLM Stats Score at 32.1 and 31.1.
In the 2 individual benchmarks reported for both models, Claude Sonnet 4.5 wins 2; this is a narrower head-to-head signal than the composite indexes.
On price, o3 is roughly 1.7x cheaper per token on a blended 3:1 input/output basis, which adds up quickly at production volume.
Based on current LLM Stats indexes, shared benchmarks, pricing, and model metadata for 2026.
Choose Claude Sonnet 4.5
- your work emphasizes agents — it leads those capability indexes
- you value its reported benchmark strengths — it wins 2 of 2 exact shared results
- you want the most recent training data — it shipped Sep 2025
Choose o3
- cost matters — it's about 1.7x cheaper per token
At a glance
The differences that matter most.
Capability indexes
Additional strengths measured across groups of related public benchmarks
Individual benchmarks
9 reported for Claude Sonnet 4.5 · 22 for o3
Claude Sonnet 4.5 outperforms in 2 benchmarks (AIME 2025, GPQA), while o3 is better at 0 benchmarks.
Claude Sonnet 4.5 significantly outperforms across most benchmarks.
Human preference
Blind head-to-head votes and playground preference scores
Pricing Analysis
Price comparison per million tokens
For input processing, Claude Sonnet 4.5 ($3.00/1M tokens) is 1.5x more expensive than o3 ($2.00/1M tokens).
For output processing, Claude Sonnet 4.5 ($15.00/1M tokens) is 1.9x more expensive than o3 ($8.00/1M tokens).
In conclusion, Claude Sonnet 4.5 is more expensive than o3.*
* 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 can generate longer responses up to 100,000 tokens, while Claude Sonnet 4.5 is limited to 64,000 tokens.
Input capabilities
Documented input modalities across available providers
Both Claude Sonnet 4.5 and o3 support multimodal inputs.
They are both capable of processing various types of data, offering versatility in application.
Claude Sonnet 4.5
o3
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 was released on 2025-04-16.
Claude Sonnet 4.5 is 6 months newer than o3.
Sep 29, 2025
11 months ago
5mo newerApr 16, 2025
1.4 years ago
Knowledge Cutoff
When training data ends
Claude Sonnet 4.5 has a knowledge cutoff of 2025-01-31, while o3 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 (2024-05-31).
Jan 2025
8 mo newerMay 2024
Provider Availability
Claude Sonnet 4.5 is available from Anthropic. o3 is available from OpenAI.
Claude Sonnet 4.5
o3
Outputs Comparison
Judge for yourself.
Run your own prompts against Claude Sonnet 4.5 and o3 side-by-side, then vote on the output you prefer.
FAQ
Common questions about Claude Sonnet 4.5 vs o3.