Eup and Myeon Hoengseong-eup Ucheon-myeon Anheung-myeon Dunnae-myeon Gapcheon-myeon Cheongil-myeon Gonggeun-myeon Seowon-myeon Gangnim-myeon
Area(㎢) 72.41 94.81 96.37 128.08 123.37 133.63 129.3 123.43 96.37
Composition(%) 7.3 9.5 9.7 12.8 12.4 13.4 13 12.4 9.7

Due to the the Taebaek Mountains, Hoengseong-gun mostly consists of hills and mountains as with other regions of Gangwon Province. However, the northeastern region of the county consists of much bigger and steep mountains and the terrain is less steeper, more spacious and rich in the southwest. The county has a big altitude difference. The 100m altitude of Hoengseop is the lowest altitude in the county and the plains in Dunnae-myeon are located at 500m altitude.

Mt. Taegi (1,264m), Mt. Cheongtae (1,190m), Mt. Bongbok n(1,028m), and Mt. Unmu (980m) form a mountain range in the northeast. In the north, there are 900m-range mountains, such as Suribong (1,028m), Mt. Balgyo (998.4m), and Mt. Oeumsan (930m). In the east are Mt. Saja (1,040m) and Mt. Baehyang (808m) and in the south are Namdaebong (1,181.5m), Hyangnobong (1.040m), Birobong (1,288m) and Mt. Maehwa (1,084m) in the Chiaksan National Park. Seongjibong (791m) in the west is the highest mountain in the county. An interesting fact is that, except of the Mt. Bongbok, all the mountains are located along the borders and surround the county in a circular form.

All rivers belong to the Namhan River System. There is a total of 18 rivers including 1 provincial river and 17 local rivers. All rivers in Hoengseong, Ucheon, Gapcheon, Cheongil, and Gonggeun join together in Hoengseong-eup to form the Seomgang River. Streams and rivers in Dunnae-myeon, Anheung-myeon, and Gangnim-myeon the Jucheon River in Anheung and flow through Yeongwol-gun and the rivers in Seowon-myeon joins the Okgye Stream and lower Namhangang in Wonju.

Hwaseongdeul (Apdeul) in Hoengseong-eup and Munamdeul in Ucheon-myeon are two major plains in Heoseong. Since, plains are so scarce in Gangwon Province Hoengseong Apdeul is regarded as the richest and largest plain in the province and it also appears in an old saying, "Hoengseong people’s pride in Apdeul." but with changing times, the plain is also going through various development projects.