Claude Fable 5 vs Claude Sonnet 5
Head-to-head technical comparison of intelligence, capabilities, and API pricing.
Which should you use?
Claude Fable 5 leads on the composite index by 1.6 points (96.4 vs 94.8).
Cost is the sharper difference: Claude Fable 5 is 5x the input price of Claude Sonnet 5 ($10 against $2 per 1M), so at volume the choice is usually decided by budget rather than benchmarks.
Pick Claude Fable 5 when
- Higher composite index — 96.4 against 94.8, a gap of 1.6 points.
- Ahead on Arena Elo by 35 points (1507 vs 1472), which is outside the board's published confidence intervals.
- Stronger on MMLU-Pro: 95.6% against 94.6%.
Pick Claude Sonnet 5 when
- Cheaper input tokens — $2 against $10 per 1M, so Claude Fable 5 costs 5x as much to feed.
- Better value per point of measured capability: $0.021 per index point against $0.104.
Value per point of measured capability, at list input pricing: Claude Sonnet 5 $0.021 · Claude Fable 5 $0.104 per index point. Run your own token mix through the token cost calculator — a comparison at list price ignores caching and batch discounts, which move real bills more than this gap does.
Where these numbers come from
Figures as of 2026-09-14. Arena Elo and pricing are read from the public board and each vendor's own pricing page; see the full leaderboard for all 34 models and which columns are measured rather than estimated, or the benchmark matrix for scores benchmark by benchmark.
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