Claude Fable 5.1 vs Claude Opus 5.5: which API costs less?
Averaged across three realistic workloads, Claude Opus 5.5 is about 59% cheaper than Claude Fable 5.1. 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 Fable 5.1Anthropic | $10 | $50 | $0.250 |
| Claude Opus 5.5Anthropic | $4 | $20 | $0.200 |
Claude Fable 5.1: Anthropic's most capable model.
Monthly cost, side by side
| Workload | Claude Fable 5.1 | Claude Opus 5.5 | Difference |
|---|---|---|---|
Customer-support chatbot 2M input + 0.5M output tokens/month, 60% of input served from prompt cache | $33.30 | $13.44 | Claude Opus 5.5 −60% |
RAG / document Q&A 20M input + 1M output tokens/month, 70% cached (shared context) | $114 | $46.80 | Claude Opus 5.5 −59% |
Agentic coding assistant 50M input + 5M output tokens/month, 80% cached (long sessions) | $360 | $148 | Claude Opus 5.5 −59% |
Your traffic looks different? Run your own numbers in the calculator.
FAQ
Which is cheaper: Claude Fable 5.1 or Claude Opus 5.5?
Across three realistic workloads (chatbot, RAG, agent), Claude Opus 5.5 works out about 59% cheaper than Claude Fable 5.1 on average. Raw rates: Claude Fable 5.1 $10/$50 per 1M tokens vs Claude Opus 5.5 $4/$20. Verified 2026-10-17.
Does prompt caching change the comparison?
Yes — cached input costs $0.250 on Claude Fable 5.1 and $0.200 on Claude Opus 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.