Compare / Claude Sonnet 4.5 vs grok-4-fast-reasoning
Claude Sonnet 4.5 vs grok-4-fast-reasoning
12 results from 3 sources that measured both models. Each row is in the source's own units; there is no overall winner.
| Benchmark | Metric | Claude Sonnet 4.5 | grok-4-fast-reasoning |
|---|---|---|---|
| Arena (formerly LMArena)reported | OverallArena rating | 1,449 | 1,417 |
| Arena (formerly LMArena)reported | Business, management and financeArena rating | 1,461 | 1,403 |
| Arena (formerly LMArena)reported | Creative writingArena rating | 1,454 | 1,383 |
| Arena (formerly LMArena)reported | Expert promptsArena rating | 1,498 | 1,421 |
| Arena (formerly LMArena)reported | Instruction followingArena rating | 1,464 | 1,389 |
| Arena (formerly LMArena)reported | OverallArena rating | 1,457 | 1,405 |
| Arena (formerly LMArena)reported | Writing, literature and languageArena rating | 1,454 | 1,388 |
| UGI Leaderboardreported | Requested-length error% off the requested word count | 5.0% | 23.0% |
| UGI Leaderboardreported | Style adherencescore from 0 to 1 | 0.41 | 0.33 |
| UGI Leaderboardreported | Writing scorescore out of 100 | 66.9 | 53.4 |
| Vectara Hallucination Leaderboardreported | Answer rate% of documents | 95.6% | 99.5% |
| Vectara Hallucination Leaderboardreported | Hallucination rate% of summaries | 12.0% | 20.2% |
Bold green marks the better value on that metric. Where a source reports ranges that overlap, the difference may not be meaningful; see the benchmark page for ranges.