Claude Opus 5 vs GPT-5.5
The comparison
On LM Arena, Claude Opus 5 scores higher (1494 Elo vs 1481 Elo), from a smaller review base (19,353 vs 55,130 Arena votes).
As of Aug 12, 2026, Claude Opus 5 is rated 1494 Elo on LM Arena (19,353 Arena votes); GPT-5.5 is rated 1481 Elo on LM Arena (55,130 Arena votes). No source is blended; each stands on its own.
Claude Opus 5
1494 EloLM Arenahigher
19,353Arena votes
GPT-5.5
1481 EloLM Arena
55,130Arena voteslarger base