How to Measure Stack and Reach on a Bike?

Measuring stack and reach accurately is critical for translating your fit from one frame to another. To perform this measurement manually, start by placing your bike on a level surface, preferably held upright in a trainer. The reference point for both measurements is the center of the Bottom Bracket (BB). Stack is the vertical distance from the center of the BB to the center of the top of the head tube. To find this, you can use a plumb line or a long spirit level to mark the height of the head tube center and measure the vertical drop to the BB center.

Reach is the horizontal distance from the BB center to the center of the head tube. You can determine this by measuring the horizontal distance between the vertical line passing through the BB and the vertical line passing through the head tube center. Avoid measuring along the tubes themselves, as tube angles will distort the result. By using these two X and Y coordinates, you create a standardized metric that allows you to compare different bike brands regardless of seat tube angles or sloping top tubes.