(1919) Kerns has an area, , of . Of this area, 46.7% is used for agricultural purposes, while 28.8% is forested. Of the rest of the land, 2.5% is settled (buildings or roads) and the remainder (21.9%) is non-productive (rivers, glaciers or mountains). The municipality is located on a terrace on the south-west slope of the
Stanserhorn and Arvigrat mountains in the
Sarneraatal and
Melchtal valleys. It is the largest municipality in the canton. It consists of the village of Kerns with the sections of Dorf, Siebeneich, Wisserlen, Halten and Dietried, the
hamlets of Sankt Niklausen and Melchtal as well as the resort of Melchsee-Frutt. ==Demographics==