Stack and reach, explained properly

Stack is the vertical distance from the bottom bracket to the top of the head tube; reach is the horizontal distance. Together they locate the front of the bike relative to your feet, which is why they replaced top tube length as the numbers that matter.

Monsoon Cycles, Colorado Springs · Updated August 16, 2026

Old geometry charts led with top tube length, which lies: a slack seat angle stretches the top tube without moving the bars a millimeter farther from your feet. Stack and reach measure from the bottom bracket, where your feet actually are, to the head tube top, where your hands actually go, so they compare honestly across brands, angles, and eras.

Using them

• Two bikes with matching stack and reach will put your contact points in the same place, whatever the tubes between look like.
• Reach changes about 1mm for every 1mm of stem, so small deltas are stem-solvable; stack deltas beyond spacer range are not.
• The ratio (stack divided by reach) is a fast character read: race bikes sit near 1.4, endurance near 1.5, upright tourers higher still.

Play with it live: open any preset in the Frame Lab and watch stack and reach respond as you move angles and lengths. The solver behind those numbers was validated against factory charts to under a millimeter.

Questions riders actually ask

Is bigger reach faster?

Longer reach is lower-and-longer positioning only if your body wants it. It is a fit dimension, not a speed dimension.

Why do manufacturers still print top tube length?

Habit, and it does matter for standover and aesthetics. But compare bikes with stack and reach first.