Claude Sonnet 4.5 vs OpenAI o3

Benchmarks, API pricing and specs, head to head. Data updated 2026-06-10.

Claude Sonnet 4.5

Anthropic · Sep 2025

65.5

The model that made 30-hour autonomous coding sessions real — 77.2% SWE-bench Verified and a 1M-token context beta at $3/$15.

OpenAI o3

OpenAI · Apr 2025

68.9

OpenAI's dedicated 2025 reasoning model that pioneered thinking-with-images and agentic tool use within chain-of-thought.

The verdict

OpenAI o3 wins 3 of the 5 benchmarks these models share, against 2 for Claude Sonnet 4.5. OpenAI o3 is about 1.7x cheaper per blended million tokens (3:1 input:output mix).

Benchmark head-to-head 2–3

SWE-bench Verified
77.2%69.1%
Claude Sonnet 4.5OpenAI o3
GPQA Diamond
83.4%83.3%
Claude Sonnet 4.5OpenAI o3
AIME 2025
87%88.9%
Claude Sonnet 4.5OpenAI o3
HLE
~17.3%20.3%
Claude Sonnet 4.5OpenAI o3
MMMU
~77.8%82.9%
Claude Sonnet 4.5OpenAI o3

Specs & pricing

Claude Sonnet 4.5OpenAI o3
modhub Index65.568.9
Input price / 1M$3$2
Output price / 1M$15$8
Context window200K200K
Max output64K100K
Open weightsnono
Reasoning modelyesyes
Multimodal inputtext, imagetext, image
Knowledge cutoffJan 2025May 2024
ReleasedSep 2025Apr 2025
Example monthly cost*$52.50$32.00

* 10M input + 1.5M output tokens per month at list prices, no caching. Green = better value on that row.

Frequently asked questions

Which is better, Claude Sonnet 4.5 or OpenAI o3?
OpenAI o3 wins 3 of the 5 benchmarks these models share, against 2 for Claude Sonnet 4.5. OpenAI o3 is about 1.7x cheaper per blended million tokens (3:1 input:output mix).
Which is cheaper, Claude Sonnet 4.5 or OpenAI o3?
Claude Sonnet 4.5 costs $3/$15 per million input/output tokens, while OpenAI o3 costs $2/$8. For a typical workload of 10M input and 1.5M output tokens per month, that's $52.50 versus $32.00.
Which model is better for coding, Claude Sonnet 4.5 or OpenAI o3?
On SWE-bench Verified — the standard agentic-coding benchmark — Claude Sonnet 4.5 scores 77.2% versus 69.1% for OpenAI o3, making Claude Sonnet 4.5 the stronger pick for coding agents.

More comparisons

Claude Sonnet 4.5 vs GPT-5.5OpenAI o3 vs GPT-5.5Claude Sonnet 4.5 vs GPT-5.2OpenAI o3 vs GPT-5.2Claude Sonnet 4.5 vs GPT-5.1OpenAI o3 vs GPT-5.1Claude Sonnet 4.5 vs GPT-5OpenAI o3 vs GPT-5Claude Sonnet 4.5 vs GPT-5 miniOpenAI o3 vs GPT-5 miniClaude Sonnet 4.5 vs Claude Fable 5OpenAI o3 vs Claude Fable 5