Claude Sonnet 4.5 vs Claude Mythos 5.1
Detailed pricing comparison and cost analysis.
Updated September 2026
Cost Simulator
| Feature | Claude Sonnet 4.5 | Claude Mythos 5.1 |
|---|---|---|
| Provider | Anthropic | Anthropic |
| Input Price (1M) | $3.00 | $10.00 |
| Output Price (1M) | $15.00 | $50.00 |
| Context Window | 200,000 | 1,000,000 |
Verdict
Claude Sonnet 4.5 costs $3.00 per 1M input tokens and $15.00 per 1M output tokens. Claude Mythos 5.1 costs $10.00 per 1M input tokens and $50.00 per 1M output tokens. Claude Sonnet 4.5 is 70% cheaper on input tokens than Claude Mythos 5.1. For output tokens, Claude Sonnet 4.5 is the more affordable option at $15.00/1M vs $50.00.
On context window, Claude Mythos 5.1 supports 1,000,000 tokens — meaning it can fit more conversation history, documents, or code in a single request. This matters for RAG pipelines, long document analysis, and agentic workflows where context builds up over many turns.
When to choose Claude Sonnet 4.5
- ✓ You need the lowest input token cost ($ 3.00/1M)
- ✓ Your workload is output-heavy — Claude Sonnet 4.5 generates text cheaper
- ✓ You are already integrated with Anthropic
When to choose Claude Mythos 5.1
- ✓ You need a larger context window (1,000,000 tokens)
- ✓ You are already integrated with Anthropic
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 Claude Mythos 5.1? ▼
Claude Sonnet 4.5 is cheaper on input tokens at $3.00/1M vs $10.00/1M for Claude Mythos 5.1 — a 70% saving.
What is the context window of Claude Sonnet 4.5 vs Claude Mythos 5.1? ▼
Claude Sonnet 4.5 has a 200,000-token context window. Claude Mythos 5.1 has a 1,000,000-token context window. Claude Mythos 5.1 supports the larger context, suitable for longer documents and agentic workflows.
Which model is better: Claude Sonnet 4.5 or Claude Mythos 5.1? ▼
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 Mythos 5.1 supports 1,000,000 tokens. Use the comparison table above to find the right fit for your workload.