Bike Fit
Calculator.
Enter your height, inseam and riding style to get every key fit number: saddle height, setback, bar drop, reach, stem length, crank length, bar width and frame size.
Results update as you type. Your body measurements follow the units you picked. Crank length, stem length, handlebar width and frame size stay in mm and cm because that is how those parts are sold in the US too: you buy a 170 mm crank, 42 cm bars and a 56 cm frame, not an inch size. Change one thing at a time, in 5 mm steps, and ride for a few sessions before judging.
How the calculator works
Almost every fit number scales off two measurements: your inseam, which drives everything vertical, and your upper body length (height minus inseam), which drives everything horizontal.
Set saddle height first and leave it alone for a week. Then set setback, then reach and drop. Changing all three at once makes it impossible to tell what helped and what hurt.
Bike fit FAQ
Stand barefoot with your back against a wall, feet about 6 inches apart. Pull a hardback book up between your legs until it presses firmly against your crotch, level like a saddle. Mark the top edge of the book on the wall and measure straight down to the floor. That is your cycling inseam, and it is usually 1 to 2 inches longer than your trouser inseam.
The most widely used method is the LeMond formula: inseam multiplied by 0.883 gives the distance from the centre of the bottom bracket to the top of the saddle, measured along the seat tube. A 33 inch (84 cm) inseam gives roughly 74.2 cm. Treat it as a starting point, then fine tune within about a centimetre either way based on how your hips feel.
Rocking hips, pointed toes at the bottom of the stroke, pain at the back of the knee and sliding forward on the nose are the classic signs of a saddle that is too high. A saddle that is too low usually shows up as pain at the front of the knee and a cramped, choppy pedal stroke. Adjust in 5 mm steps and ride for a week before judging.
Setback is how far the saddle nose sits behind a vertical line through the bottom bracket. It sets where your hips sit relative to the pedals, which changes how you load your quads and glutes. Road racers typically run 6 to 8 cm of setback, endurance riders 5 to 7 cm, mountain bikers 4 to 6 cm and time triallists close to zero or even ahead of the bottom bracket.
Drop is the height difference between the top of the saddle and the top of the bars. Flexible racers run 8 to 12 cm, most club riders sit between 4 and 8 cm, and riders with tight hamstrings or a stiff lower back are better off at 0 to 4 cm. Start high and lower the bars gradually as your flexibility improves.
Crank length scales with leg length. A common guide is inseam in centimetres multiplied by 1.25, plus 65, which puts most riders between 165 and 175 mm. Shorter cranks open the hip angle at the top of the stroke, which helps riders with hip or lower back restrictions and lets you hold an aero position more comfortably.
No. These numbers give you a solid, well tested starting position that will suit most riders, and they are far better than guessing. A professional fitter watches you actually pedal, checks for leg length differences, foot issues and asymmetry, and adjusts cleats. If you ride a lot or have persistent pain, a real fit is worth the money.