Specs for the Taper on Classical Round Columns

Quick advice on information sources for laying out classic architectural shapes and forms. January 9, 2015

Question (WOODWEB Member) :
What is the exact formula for the taper on classical round columns? I've heard that the bottom 1/3 is straight and the top 2/3 has a curved taper. I am looking for the precise formula for this top taper - preferably as a ratio so I can apply it to a variety of column sizes. If the 1/3 mark is 10" diameter, what should the diameter be at the top - 9"? I can guess and experiment as well as the next guy but I am hoping that someone reading this has found the exact formula. I’d rather not reinvent the wheel, or, the column.

Forum Responses
(Architectural Woodworking Forum)
From Contributor T:
Usually the taper or entasis starts at 1/3 of the column length measured from the base. The diameter of the top is usually 5/6 of diameter of the base. A lot of these numbers depend on the order (Doric, Tuscan). The book "American Vignola" by William R. Ware has helped me very much in figuring out classical dimensions and proportions.

From contributor R:
There are a number of good references for this. One of the more useful is the Gentleman’s and cabinetmakers director by Thomas Chippendale. Still available today the first part of the book explains the orders of architecture, proportions, and how to layout or draft them. It is all you need.