Claude Sonnet 4.5 vs o3-pro
Detailed pricing comparison and cost analysis.
Updated September 2026
Cost Simulator
| Feature | Claude Sonnet 4.5 | o3-pro |
|---|---|---|
| Provider | Anthropic | OpenAI |
| Input Price (1M) | $3.00 | $20.00 |
| Output Price (1M) | $15.00 | $80.00 |
| Context Window | 200,000 | 200,000 |
Verdict
Claude Sonnet 4.5 costs $3.00 per 1M input tokens and $15.00 per 1M output tokens. o3-pro costs $20.00 per 1M input tokens and $80.00 per 1M output tokens. Claude Sonnet 4.5 is 85% cheaper on input tokens than o3-pro. For output tokens, Claude Sonnet 4.5 is the more affordable option at $15.00/1M vs $80.00.
On context window, Claude Sonnet 4.5 supports 200,000 tokens — meaning it can fit more conversation history, documents, or code in a single request. This matters for RAG pipelines, long document analysis, and agentic workflows where context builds up over many turns.
When to choose Claude Sonnet 4.5
- ✓ You need the lowest input token cost ($ 3.00/1M)
- ✓ Your workload is output-heavy — Claude Sonnet 4.5 generates text cheaper
- ✓ You are already integrated with Anthropic
When to choose o3-pro
- ✓ You are already integrated with OpenAI
Use the calculator above to simulate your specific workload and find the exact break-even point. For most applications, the cheapest model is the one that minimises your total monthly bill given your input-to-output token ratio.
Frequently Asked Questions
Is Claude Sonnet 4.5 cheaper than o3-pro? ▼
Claude Sonnet 4.5 is cheaper on input tokens at $3.00/1M vs $20.00/1M for o3-pro — a 85% saving.
What is the context window of Claude Sonnet 4.5 vs o3-pro? ▼
Claude Sonnet 4.5 has a 200,000-token context window. o3-pro has a 200,000-token context window. Claude Sonnet 4.5 supports the larger context, suitable for longer documents and agentic workflows.
Which model is better: Claude Sonnet 4.5 or o3-pro? ▼
The best choice depends on your use case. For cost efficiency on input tokens, Claude Sonnet 4.5 is the cheaper option. For maximum context length, Claude Sonnet 4.5 supports 200,000 tokens. Use the comparison table above to find the right fit for your workload.