Purpose: To evaluate the recent intraoperative lagophthalmos formula method for levator resection in determining postoperative lid height in congenital ptosis on Egyptian patients. Methods: This is a prospective case series which included 20 eyelids of 17 Egyptian children with congenital ptosis whose levator function is 4 mm or better. They underwent levator muscle resection guided by the recently presented intraoperative lagophthalmos formula. Preoperative Margin-to-Reflex Distance 1 (MRD1) and levator function were measured then intraoperative palpebral fissure opening was determined from formula: Intraoperative lagophthalmos = 9.08 − (0.48 × Preoperative MRD1) − (0.26 × Levator function). Success was defined as postoperative MRD1 ⩾ 3 mm and difference between both eyelid height ⩽1 mm at 6 months. Results: From 20 eyelids, there were five cases with mild (25%), 11 with moderate (55%), and four with severe (20%) ptosis. They showed success in four cases (80%), eight cases (73%), and three cases (75%) in each degree respectively with an overall success of 15 cases (75%). Conclusion: Proposed intraoperative lagophthalmos formula showed relatively good results in predicting postoperative eyelid level in Egyptian children with simple congenital ptosis with fair to good levator function.