Buffer cache hit ratio - oracle database script

SELECT ROUND((1-(phy.value / (cur.value + con.value)))*100, 2) "Cache Hit Ratio"
FROM v$sysstat cur,
     v$sysstat con,
     v$sysstat phy
WHERE cur.name = 'db block gets'
  AND con.name = 'consistent gets'
  AND phy.name = 'physical reads' /