To get your accurate size, lay a well-fitting garment you currently own flat onto a level surface.  Measure across the front only from armpit to armpit and then vertically down the exact middle from neck to hem to find your closest match. 

Due to the naturally malleable properties of wool please allow for a tolerance of 2-3cm.

MEN'S VINTAGE WAISTCOAT SIZINGXSSmallMediumLargeXL
Chest Width (Armpit to Armpit)43cm46cm49cm52cm55cm
Length (Centre back to base of hem)62cm62cm64cm64cm66cm