Claude Fable 5.1 API cost calculator
Claude Fable 5.1 (Anthropic) is priced at $10 per million input tokens, $0.25 for cached input, and $50 per million output tokens — half that through the Batch API. Verified 2026-09-17 against Anthropic's pricing page.
Cache reads on Fable 5.1 are 2.5% of the input price ($0.25/M), versus 10% on every other Claude model.
What Claude Fable 5.1 costs for common workloads
| Workload | Per request | Per day | Per month |
|---|---|---|---|
| Support chatbotShort turns with a reused system prompt — 3k in, 400 out, 60% cached. | $0.032 | $162 | $4,868 |
| RAG over documentsRetrieved context dominates — 12k in, 500 out, 30% cached. | $0.110 | $165 | $4,946 |
| Coding agentGrowing context every turn — 20k in, 1.5k out, 80% cached. | $0.119 | $357 | $10,710 |
| Batch classificationTiny prompts at volume through the Batch API — 800 in, 20 out. | $0.0045 | $900 | $27,000 |
Its blast radius when an agent loops
The coding-agent workload above at 30 requests a minute — $214 an hour — priced at each point a team usually finds out:
Hourly alert
$214
Next morning
$5,141
After a weekend
$12,852
Monthly invoice
$154,224