Type your monthly token usage and compare the real API bill for Fable 5, Opus 4.8 and GPT-5.5 — side by side.
Anthropic released Claude Fable 5 on June 9, 2026 at $10 / 1M input and $50 / 1M output tokens — exactly double the standard rate of Claude Opus 4.8 ($5 / $25). GPT-5.5 sits in between at $5 / $30. The calculator above turns those per-token rates into a monthly bill for your actual usage, because the only number that matters is what you'd really pay.
Only if your high-value tasks actually improve. Fable 5 leads on most benchmarks (coding, long-context, reasoning), but for everyday writing and summarizing, Opus 4.8 at half the price is often the smarter spend. Run your top 2–3 real workloads on both before committing.
Mythos 5 is the same underlying model as Fable 5 with some safeguards lifted. It is not available to the public — it's deployed only to select cyberdefenders and infrastructure partners. Everyone else uses Fable 5, which blocks high-risk areas like cybersecurity and biology.
Output tokens dominate the bill (they're 5× the input rate on Fable 5). Keep responses tight, cache repeated system prompts (GPT-5.5 caches drop 90%), and route cheap/simple calls to Opus 4.8 or a smaller model.
Built by the same maker — try these too.