在几何学中，锥台又称平截头体，指的是圆锥或棱锥被两个平行平面所截后，位于两个平行平面之间的立体。根据所截的是圆锥还是棱锥，可分为圆台与棱台。

棱台或圆台的体积是原立体图形的体积减去被截去部分的体积：

B₁ 指一个底面的面积，B₂指另一个底面的面积, and h₁， h₂ 指原顶点分别到两底面的面积。 考虑到

这个体积也可用平截头体的高 h = h₂−h₁ 与两底面面积的希罗平均数表达：

亚历山大里亚的希罗 推导出了这个公式并且凭借它遇到了虚数。

特别地， 圆台的体积是

π 等于 3.14159265...，'R₁, R₂ 是两底面的半径。

In geometry, a frustum (plural: frusta or frustums) is the portion of a solid (normally a cone or pyramid) that lies between two parallel planes cutting it. A right frustum is a parallel truncation of a right pyramid.

The term is commonly used in computer graphics to describe the three-dimensional region which is visible on the screen, the "viewing frustum", which is formed by a clipped pyramid; in particular, frustum culling is a method of hidden surface determination.