Claude Opus 5.5 vs Claude Sonnet 5.5: which API costs less?
Averaged across three realistic workloads, Claude Sonnet 5.5 is about 50% cheaper than Claude Opus 5.5. Below: raw rates and side-by-side monthly costs, computed from prices verified 2026-10-17 (we track what you are billed today, promos included).
Rates per 1M tokens
| Model | Input | Output | Cached input |
|---|---|---|---|
| Claude Opus 5.5Anthropic | $4 | $20 | $0.200 |
| Claude Sonnet 5.5Anthropic | $2 | $10 | $0.100 |
Monthly cost, side by side
| Workload | Claude Opus 5.5 | Claude Sonnet 5.5 | Difference |
|---|---|---|---|
Customer-support chatbot 2M input + 0.5M output tokens/month, 60% of input served from prompt cache | $13.44 | $6.72 | Claude Sonnet 5.5 −50% |
RAG / document Q&A 20M input + 1M output tokens/month, 70% cached (shared context) | $46.80 | $23.40 | Claude Sonnet 5.5 −50% |
Agentic coding assistant 50M input + 5M output tokens/month, 80% cached (long sessions) | $148 | $74.00 | Claude Sonnet 5.5 −50% |
Your traffic looks different? Run your own numbers in the calculator.
FAQ
Which is cheaper: Claude Opus 5.5 or Claude Sonnet 5.5?
Across three realistic workloads (chatbot, RAG, agent), Claude Sonnet 5.5 works out about 50% cheaper than Claude Opus 5.5 on average. Raw rates: Claude Opus 5.5 $4/$20 per 1M tokens vs Claude Sonnet 5.5 $2/$10. Verified 2026-10-17.
Does prompt caching change the comparison?
Yes — cached input costs $0.200 on Claude Opus 5.5 and $0.100 on Claude Sonnet 5.5. Our scenario numbers already include realistic cache hit rates.
Is cheaper always better?
No. Price is one axis — model capability, context window and latency differ. This page answers only the cost question; benchmark quality on your own tasks before switching.