[3] Hergiswil bei Willisau has an area, as of 2006[update], of 31.3 km2 (12.1 sq mi).

Of the rest of the land, 3.5% is settled (buildings or roads) and the remainder (0.5%) is non-productive (rivers, glaciers or mountains).

Of the settled areas, 1.72% is covered with buildings, 0.06% is industrial, 0.19% is classed as special developments, 0.1% is parks or greenbelts and 1.47% is transportation infrastructure.

[5] The municipality is located in the upper valley of the Enziwigger river in the northern Napfgebiet.

Most of the population (as of 2000[update]) speaks German (98.0%), with Albanian being second most common ( 0.8%) and Serbo-Croatian being third ( 0.3%).

The age distribution, as of 2008[update], in Hergiswil bei Willisau is; 499 people or 27.7% of the population is 0–19 years old.

In the 2000 census[update], the religious membership of Hergiswil bei Willisau was; 1,557 (86.1%) were Roman Catholic, and 136 (7.5%) were Protestant, with an additional 12 (0.66%) that were of some other Christian faith.