Rainwater harvesting is the collection of rainwater and runoff from catchment areas such as roofs or other urban surfaces. Collected water has productive end-uses such as irrigation, industry, domestic, and can recharge groundwater. Sulaimani heights have been selected as a study area, which is located in Sulaimani Governorate in Kurdistan Region, North Iraq. The main objective of this study was to estimate the amount of harvested rainwater form Sulaimani heights urban area in Sulaimani City. Three methods for runoff calculation have been compared, the storm water management model (SWMM), the soil conservation service (SCS) method, and the runoff coefficient (RC) using daily rainfall data from 1991 to 2019. The annual harvested runoff results with the three different methods SWMM, SCS, and RC were estimated as 836,470 m3, 508,454 m3, and 737,381 m3, respectively. The results showed that SWMM method has the highest runoff result and could meet 31% of the total demand of the study area and 28% and 19% for RC and SCS methods, respectively.