Side-by-side technical and economic comparison between Anthropic's Claude Fable 5.1 and Anthropic's Claude Opus 5.
| Metric | Claude Fable 5.1 | Claude Opus 5 | Advantage |
|---|---|---|---|
| Provider Organization | Anthropic | Anthropic | — |
| Standard Input / 1M | $10.00 | $5.00 | Claude Opus 5 (50% lower) |
| Cached Input / 1M | $0.25 | $0.50 | Claude Fable 5.1 lower |
| Output / 1M | $50.00 | $25.00 | Claude Opus 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 Opus 5 |
|---|---|---|
| Chatbot10k requests · 500 in / 200 out | $150.00 | $75.00 |
| RAG app100k requests · 8,000 in / 1,200 out | $14,000.00 | $7,000.00 |
| Coding agent100k requests · 12,000 in / 2,000 out | $22,000.00 | $11,000.00 |
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 Opus 5 when looking for Anthropic's tooling integration, specific context window depth (1M tokens), or when output generation volume favors its $25/M rate.
At a typical 3:1 input-to-output token mix, Claude Opus 5 is about 50% cheaper than Claude Fable 5.1. Claude Fable 5.1 costs $10 per 1M input and $50 per 1M output tokens; Claude Opus 5 costs $5 and $25.
Both models have a 1M-token context window.
Claude Fable 5.1: yes, cached input costs $0.25/1M. Claude Opus 5: yes, cached input costs $0.5/1M.