Side-by-side technical and economic comparison between Anthropic's Claude Fable 5.1 and Anthropic's Claude Sonnet 5.
| Metric | Claude Fable 5.1 | Claude Sonnet 5 | Advantage |
|---|---|---|---|
| Provider Organization | Anthropic | Anthropic | — |
| Standard Input / 1M | $10.00 | $2.00 | Claude Sonnet 5 (80% lower) |
| Cached Input / 1M | $0.25 | $0.20 | Claude Sonnet 5 lower |
| Output / 1M | $50.00 | $10.00 | Claude Sonnet 5 lower |
| Context Window | 1M | 1M | Equal |
| Max Generation Tokens | 32k | 16.4k | Claude Fable 5.1 |
| Tokenizer Family | Anthropic Claude BPE (~65k vocabulary) | Anthropic Claude BPE (~65k vocabulary) | — |
| Workload (per month) | Claude Fable 5.1 | Claude Sonnet 5 |
|---|---|---|
| Chatbot10k requests · 500 in / 200 out | $150.00 | $30.00 |
| RAG app100k requests · 8,000 in / 1,200 out | $14,000.00 | $2,800.00 |
| Coding agent100k requests · 12,000 in / 2,000 out | $22,000.00 | $4,400.00 |
Standard rates, no caching or batch discounts. Model your own numbers below.
Opt for Claude Fable 5.1 when your engineering requirements prioritize Anthropic's ecosystem, specific tokenizer efficiencies (Calibrated Claude Tokenizer (±3%)), or when your expected prompt-to-completion ratios favor its $10/M input rate.
Opt for Claude Sonnet 5 when looking for Anthropic's tooling integration, specific context window depth (1M tokens), or when output generation volume favors its $10/M rate.
At a typical 3:1 input-to-output token mix, Claude Sonnet 5 is about 80% cheaper than Claude Fable 5.1. Claude Fable 5.1 costs $10 per 1M input and $50 per 1M output tokens; Claude Sonnet 5 costs $2 and $10.
Both models have a 1M-token context window.
Claude Fable 5.1: yes, cached input costs $0.25/1M. Claude Sonnet 5: yes, cached input costs $0.2/1M.