Although basic in design, the humble bicycle stem serves a crucial role. At the very least, the stem functions as a bridge between the handlebar and steering column, allowing the two to work in unison. More personally, a stem helps a cyclist dial in a proper fit. Stems come in multiple lengths, helping each rider achieve a comfortable reach to the handlebar. Once a comfortable stem is found, calculating its length is helpful whenever replacing the stem or purchasing a new bicycle.
Straddle the bicycle just behind the handlebars. Place a foot on either side of the front wheel, and centre the wheel.
Note the bolt atop the steering column. The bolt secures a top cap that in turn helps keep the steering column end of the stem in place. Place the tip of a measuring tape in the very centre of the bolt.
Stretch the measuring tape in the direction of the handlebar. At this end, a clamp plate joins the handlebar to the stem. Measure to where the clamp plate meets the stem, at the centre of the top of the handlebar.
Convert the measurement to metric if using a standard measuring tape. Multiply the length in inches by 2.54 to convert to centimetres. Like many bicycle parts, stem length is typically listed in either centimetres or millimetres.