Claude Sonnet 5.5 vs o3
Claude Sonnet 5.5 leads the LLM Stats Score 58.0 to 31.0. o3 is 1.1x cheaper per token.
Anthropic · OpenAI · Updated for 2026
Which is better?
Claude Sonnet 5.5 leads the overall LLM Stats Score 58.0 to 31.0, ranking #3 overall.
On price, o3 is roughly 1.1x cheaper per token on a blended 3:1 input/output basis, which adds up quickly at production volume.
Claude Sonnet 5.5 also accepts a larger context window (1,000,000 input tokens), making it the stronger choice for long documents and large codebases.
Based on current LLM Stats indexes, shared benchmarks, pricing, and model metadata for 2026.
Choose Claude Sonnet 5.5
- overall performance matters — it scores 58.0 and ranks #3 on LLM Stats
- your work emphasizes reasoning and coding — it leads those capability indexes
- you process long inputs — it offers a 1,000,000 token context window
- you want the most recent training data — it shipped Sep 2026
Choose o3
- cost matters — it's about 1.1x cheaper per token
At a glance
The differences that matter most.
Capability indexes
Additional strengths measured across groups of related public benchmarks
Individual benchmarks
47 reported for Claude Sonnet 5.5 · 22 for o3
Claude Sonnet 5.5 and o3don't have any common benchmark datasets to compare. They may have been evaluated on different testing suites.
Human preference
Blind head-to-head votes and playground preference scores
Pricing Analysis
Price comparison per million tokens
For input processing, Claude Sonnet 5.5 ($2.00/1M tokens) costs the same as o3 ($2.00/1M tokens).
For output processing, Claude Sonnet 5.5 ($10.00/1M tokens) is 1.3x more expensive than o3 ($8.00/1M tokens).
In conclusion, Claude Sonnet 5.5 is more expensive than o3.*
* Using a 3:1 ratio of input to output tokens
Context Window
Maximum input and output token capacity
Claude Sonnet 5.5 accepts 1,000,000 input tokens compared to o3's 200,000 tokens. Claude Sonnet 5.5 can generate longer responses up to 128,000 tokens, while o3 is limited to 100,000 tokens.
Input capabilities
Documented input modalities across available providers
Both Claude Sonnet 5.5 and o3 support multimodal inputs.
They are both capable of processing various types of data, offering versatility in application.
Claude Sonnet 5.5
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 5.5 was released on 2026-09-28, while o3 was released on 2025-04-16.
Claude Sonnet 5.5 is 18 months newer than o3.
Sep 28, 2026
2 days ago
1.5yr newerApr 16, 2025
1.5 years ago
Knowledge Cutoff
When training data ends
Claude Sonnet 5.5 has a knowledge cutoff of 2026-06-01, while o3 has a cutoff of 2024-05-31.
Claude Sonnet 5.5 has more recent training data (up to 2026-06-01), making it potentially better informed about events through that date compared to o3 (2024-05-31).
Jun 2026
2.1 yr newerMay 2024
Provider Availability
Claude Sonnet 5.5 is available from Anthropic. o3 is available from OpenAI.
Claude Sonnet 5.5
o3
Outputs Comparison
Judge for yourself.
Run your own prompts against Claude Sonnet 5.5 and o3 side-by-side, then vote on the output you prefer.
FAQ
Common questions about Claude Sonnet 5.5 vs o3.