Claude Opus 5 vs Claude Fable 5
Head-to-head technical comparison of intelligence, capabilities, and API pricing.
Which should you use?
Claude Opus 5 and Claude Fable 5 score within 0.2 points of each other on the composite index, which is too close to call a winner on capability alone.
Their Arena Elo differs by only 14 points, inside the confidence intervals the public board reports, so human preference does not separate them.
Cost is the sharper difference: Claude Fable 5 is 2x the input price of Claude Opus 5 ($10 against $5 per 1M), so at volume the choice is usually decided by budget rather than benchmarks.
Pick Claude Opus 5 when
- Stronger on MMLU-Pro: 95.7% against 95.6%.
- Cheaper input tokens — $5 against $10 per 1M, so Claude Fable 5 costs 2x as much to feed.
- Better value per point of measured capability: $0.052 per index point against $0.104.
Pick Claude Fable 5 when
On these measures Claude Fable 5 does not lead Claude Opus 5 anywhere, so pick it only for reasons outside this table — an existing integration, a region, or a contract.
Value per point of measured capability, at list input pricing: Claude Opus 5 $0.052 · 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 2026-09-07. 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.