This site makes a distinction between US stone (12.5 lb/st) and UK stone (14 lb/st). I can find no corroboration of the "US stone" conversion factor.
UK stone: 9.133436576 (9 st 1.9 lb)
US stone: 10.229448965
UK stone: 9.133436576 (9 st 1.9 lb)
US stone: 10.229448965