Saddle Height & Frame Size Calculator
Get your saddle height and a suggested road or mountain bike frame size from your inseam, using the LeMond method.
How to measure: stand barefoot with a book wedged firmly between your legs like a saddle, spine up. Measure from the floor to the top edge of the book's spine — that's your inseam.
Suggested road frame size: 53.2 cm
Suggested MTB frame size: 18.1 in
This is a starting point, not a bike fit. Crank length, cleat stack height, and your own flexibility all shift the ideal saddle height a bit. Modern frames with sloping top tubes also make "frame size" a softer number than it used to be, so treat it as a sizing zone, not a fixed target. If your knees hurt on longer rides, get a proper fit instead of chasing a number.
How it works
This uses the LeMond method, a formula pro road racer Greg LeMond's coach popularized in the 1980s and one that still holds up as a solid starting point today. It takes your inseam, measured the specific way described above, and multiplies it by a fixed ratio to get saddle height, then applies two more ratios to suggest a road and mountain bike frame size in the same move.
Worked example: an 80 cm inseam. Saddle height works out to 80 × 0.883 = 70.6 cm, measured from the center of the bottom bracket up along the seat tube to the top of the saddle. The same inseam suggests a 53.2 cm road frame (measured seat-tube center to top) and an 18.1 inch mountain bike frame. Someone with a 74 cm inseam, a bit shorter, lands closer to 65.3 cm of saddle height and a 49.2 cm road frame instead.
FAQ
Is this exact enough that I don't need a bike shop fit?
It gets you within a centimeter or two of a workable setup, which is enough to start riding comfortably. It doesn't account for your crank length, how far your foot sits above the pedal axle in your shoes and cleats, or how flexible your hips and hamstrings are, all of which nudge the ideal height slightly. Use this number to set your saddle, then fine-tune by feel over your first few rides.
Why do the road and MTB frame sizes use different ratios?
Road frames and mountain bike frames are measured differently and are built with different geometry in mind, road frames prioritize a longer, lower reach for aerodynamics and efficiency, while mountain bike frames run shorter and more upright for control on rough terrain. The lower ratio for MTB frames reflects that shorter, more standover- friendly sizing.
My bike has a sloping top tube. Does the frame size number still apply?
Less precisely than it used to. Frame size used to describe a level top tube's height off the ground, but most modern frames slope downward from the head tube to the seat tube, so the same rider can fit a wider range of labeled sizes. Treat the frame number here as a starting size to try, then check standover clearance and reach when you test ride it.
What if my knees hurt after I set my saddle to this height?
Knee pain, especially at the front of the knee, often means the saddle is too low, and pain at the back of the knee often means it's too high. Small adjustments, a few millimeters at a time, usually clear it up. If it doesn't improve within a couple of rides, stop guessing and get a proper bike fit from a shop, since a real fit accounts for your specific leg length, flexibility, and pedaling style.
For more on getting the fit right, see how to set your saddle height the right way, what size bike do I need, and road, hybrid, gravel, or mountain bike.