This post will explain how to measure one’s sit bone width (at home). Sit bone width is important when choosing an optimal saddle width (so it is neither too narrow, nor too wide).
Tools needed to measure sit bone width at home are relatively cheap and widely available. You are most likely to already have them at hand.
With a flat surface. Should be hard, or not too softly (thickly) padded. Height so that, when a rider is seated, their knees are bent at (about) 90 degrees angle. If a bench/chair is too high, some object can be placed under the rider’s feet, so that knees are at the right angle.
Cardboard, of some old package box. So that it is soft enough to dent under pressure. Take a nice, flat part of cardboard, about 40 cm wide and about 30 cm long (absolute minimum is 20 by 10, if one knows where to sit exactly – so that sit bones leave an imprint).
Chalk. Any colour will do – as long as it is long (about 10 cm) and (longitudinally) flat.
Of course, some kind of measuring tape. Any will do. Measured distances are below 20 cm and over 10 cm.
Place the cardboard on the bench.
Sit on the (middle part of the) cardboard with the back straight.
Body can be pressed down onto the cardboard using hands (Picture 6b), or an “assistant” can press onto the shoulders, so that a nicer and deeper imprint is made.
Stand up. 🙂
Place the chalk flat on the cardboard and paint the cardboard. Indentations made by the sit bones will remain not painted.
Find the middle of both the impressions and mark them (with a pen, or the chalk tip).
Finally, measure (in mm, because that’s how saddle widths are usually expressed) the distance between the two impression centers.
This concludes measuring sit bone width – an important factor when choosing a correct saddle width.
How to choose an optimal saddle width, based on these measurements and riding position, is explained in this post:
Optimal bicycle saddle (seat) width