A – Top tube length (center to center)
Horizontal top tube frame (some road bikes): Measure from the center of the head tube at the head tube / top tube junction to the center of the seat tube at the seat tube / top tube junction.
Sloping top tube frame (compact road bikes and mountain bikes): Measure from the center of the head tube at the head tube / top tube junction horizontally (parallel to the ground) to the center of the seat post or seat tube.

B – Stem length
Measure from the center of the steerer clamp to the center of the bar clamp, along the stem’s extension. Most stems are only available in 5mm increments and typically range from 90 – 140mm.

C – Stem angle
Using an angle finder or protractor, measure the angle between the head tube and the stem’s extension. Typical values range from 73o to 105o.

D – Saddle center to bar
Measure from the center of the saddle (at center line of seat post) to the center of the stem clamp where it holds the bar.

E – Saddle to floor
Measure from the top of the center of the saddle (at center line of seat post) to the ground vertically. A plumb line dropped from the center of the saddle helps accuracy.

F – Bar to floor
Measure from the top of the bar (next to the stem clamp) to the floor. A plumb line helps with this measurement too.

G – Head tube length
Measure the length of the head tube from end to end, not including the headset cups.

H– Front Center
Measure form the center of the bottom bracket to the center of the front axle.

I – Saddle Height
Measure along the seat tube from the center of the bottom bracket to the top of the saddle.

J - Saddles Setback
Drop plumb line from the saddles center measured at the centerline of the seat post and measure from the plumb line horizontally to the center of the bottom bracket.