# detecting ovulation with BBT > , the “coverline” method, a horizontal coverline (which means a threshold temperature) is drawn on a BBT chart. When temperature above this coverline is recorded, ovulation is suggested. The coverline can be determined by adding 0.158F to the highest temperature recorded during the first 10 days of a cycle, or by using previously recorded temperatures.[[(Su et al., 2017)#^-gy6t]] > “three over six” rule, three temperatures are required to be 0.28F above the highest point of the previous six temperatures with at least one of the higher temperatures being 0.48F above the lower ones.[[(Su et al., 2017)#^-hc9r]]