The present study aimed to introduce a new formula for classification of nodules in TI-RADS and describe ultrasonography features of benign and malignant thyroid nodules.This study was conducted on thyroid mass in 1033 patients. The incidence of malignancy for thyroid nodules was determined by selecting malignancy coefficients. Then the patients were first classified using conventional TI-RADS classification criteria and once again according to a new proposed formula.Among ultrasonography features of thyroid nodules, the irregular shape (46.7%), unclear margin (47.3%), extension to the capsule (irregular and infiltrative margin) (85%), the marked hypo-echoic nodules (63.8%), micro-calcification (49%), and to have vertical axis (74.0%) were associated with high incidence of malignancy.According to the proposed new formula for TI-RADS, there are four coefficients of 7, 3, 1 and 0 for incidence of malignancy of each one of ultrasound findings that help to standardization and unifying of TI-RADS classification. The incidence of malignancy in TI-RADS classification according to the new proposed formula was achieved as follows: group 2: 0.0%, group 3: 0.7%, groups 4a, 4b, 4c: 16.7%, 43.4%, 68.5%, and group 5: 95.2%, respectively.