Hamstring tendon has been more popularly used in anterior cruciate ligament reconstruction. Quadruple semitendinosus graft had some benefits and decreased the donor site morbidity.This study presented the length of semitendinosus and gracilis in Thai people and used the leg length to estimate the tendon graft length.Eighty five knees of adult cadaver in both sexes were measured length of semitendinosus and gracilis. The leg length was measured and calculated the correlation between graft length and leg length.The length of semitendinosus in male and female were 24.33 and 21.89 centimeters. The length of gracilis in male and female were 17.98 and 16.55 centimeters respectively. There were moderate correlation between grafts length and leg length.Thai people should use both of semitendinosus and gracilis in ACL reconstruction and leg length can effectively use as the predictor of graft length.