The municipality has a total land area of 30,511 has. The urban area occupies 1,077 hectares while the rural area totaled to 29,434. hectares. The urban area is composed of barangays Poblacion and Campaasan. The remaining 13 barangays consists the rural area.
In terms of land area, Benli has the biggest area of 9,147 hectares. The smallest area is that of Maasin, with only 231.5 hectares. It is an island barangay.