Claude Mythos 5.1 vs o3
Detailed pricing comparison and cost analysis.
Updated September 2026
Cost Simulator
| Feature | Claude Mythos 5.1 | o3 |
|---|---|---|
| Provider | Anthropic | OpenAI |
| Input Price (1M) | $10.00 | $2.00 |
| Output Price (1M) | $50.00 | $8.00 |
| Context Window | 1,000,000 | 200,000 |
Verdict
Claude Mythos 5.1 costs $10.00 per 1M input tokens and $50.00 per 1M output tokens. o3 costs $2.00 per 1M input tokens and $8.00 per 1M output tokens. o3 is 80% cheaper on input tokens than Claude Mythos 5.1. For output tokens, o3 is the more affordable option at $8.00/1M vs $50.00.
On context window, Claude Mythos 5.1 supports 1,000,000 tokens — meaning it can fit more conversation history, documents, or code in a single request. This matters for RAG pipelines, long document analysis, and agentic workflows where context builds up over many turns.
When to choose Claude Mythos 5.1
- ✓ You need a larger context window (1,000,000 tokens)
- ✓ You are already integrated with Anthropic
When to choose o3
- ✓ You need the lowest input token cost ($ 2.00/1M)
- ✓ Your workload is output-heavy — o3 generates text cheaper
- ✓ 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 Mythos 5.1 cheaper than o3? ▼
o3 is cheaper on input tokens at $2.00/1M vs $10.00/1M for Claude Mythos 5.1 — a 80% saving.
What is the context window of Claude Mythos 5.1 vs o3? ▼
Claude Mythos 5.1 has a 1,000,000-token context window. o3 has a 200,000-token context window. Claude Mythos 5.1 supports the larger context, suitable for longer documents and agentic workflows.
Which model is better: Claude Mythos 5.1 or o3? ▼
The best choice depends on your use case. For cost efficiency on input tokens, o3 is the cheaper option. For maximum context length, Claude Mythos 5.1 supports 1,000,000 tokens. Use the comparison table above to find the right fit for your workload.