The surviving pattern published in Juan de Alcega’s ‘Libro de Geometria, Practica y Traca’(1589) represents almost everything we know about the farthingale. Most articles on recreating the Alcega farthingale focus on faithfully reproducing the pattern based on fabric widths. Honestly, though, calling this a “pattern” is a bit of an overstatement: the book was more intended as a series of cutting diagrams to help tailors avoid waste. The problem is, Alcega included some rather sharp commentary on on what he considered the proper size for the bottom hoop of the farthingale, but no real information on the size of the intended wearer. Complicating things further, modern bodies aren’t build quite like the popular model of the 16th century. So what’s a costumer to do? How about some trigonometry!
Trust me, this won’t hurt.