How do I calculate mountain bike saddle height?

The same way as any other bike — saddle height (the LeMond method) is based on inseam length alone, not bike type, so it applies the same way on a road, gravel, hybrid, or mountain bike. Measure your inseam and enter it into Stamptivity Bike Fit for a starting height.

Is there a free bike stem length calculator?

Yes. Stamptivity's Bike Fit tool estimates a starting stem length and bar reach from your torso and arm length, free and entirely in your browser, no account needed. The formulas are scaled from a road-style drop-bar position, so on a flat-bar hybrid or mountain bike, treat the result as a rougher proxy rather than a target.

How do I measure my inseam, torso, and arm length for a bike fit calculator?

For inseam, stand against a wall barefoot with a book pushed up snugly between your legs and measure floor to the top of the book. For torso, sit upright and measure from the sternum notch straight down to the seat. For arm length, measure from the point of your shoulder to the tip of your middle finger with the arm relaxed.

Does a road bike fit calculator work for mountain bikes?

Partially. Saddle height and saddle setback apply the same way regardless of bike type. Stem length and bar reach are scaled from a drop-bar riding position, so they're a rougher proxy on a flat-bar MTB — Stamptivity flags this inline when you select "Mountain bike" in the bike-type selector. Crank length has no sourced target for any bike type, and on a mountain bike it also affects pedal-strike clearance, which the calculator can't assess.

Can I check if my current bike setup already fits, not just get a starting point?

Yes. Enter your current saddle height, setback, stem, and crank length, and optionally a short pedaling video, and the "Does it fit?" panel compares your setup against the formulas and the video-measured riding position — with a stated confidence level, not a guessed number to move by.

Bike Fit Calculator: Saddle Height, Stem Length & Reach (Free)

"What saddle height should I run?" and "what stem length do I need?" are two of the most common questions in any bike-fit forum, and the honest answer is always "it depends" — on your proportions, your flexibility, your riding style. But every professional fitter still starts from the same place: a set of proportional formulas based on your body measurements, before any dynamic fine-tuning on the bike.

Stamptivity's Bike Fit calculator runs those formulas for you, free, in your browser.

What the Calculator Works Out

From four body measurements — inseam, torso length, arm length, and height — Bike Fit gives you:

Saddle height — via the LeMond method, the proportional formula fitters have used as a starting point for decades
Saddle setback — via KOPS (Knee Over Pedal Spindle), shown as a general range rather than a single number
Stem length and bar reach — proportional estimates scaled from a road-style riding position

Every number is a starting point, not a final answer — flexibility, riding style, injury history, and your specific frame all matter too.

How to Measure Your Body

Accurate inputs matter more than the formula itself. Three measurements to get right:

Inseam: Stand against a wall barefoot with a book pushed up snugly between your legs (like you're sitting on a saddle), and measure from the floor to the top of the book.

Torso length: Sit upright and measure from the sternum notch straight down to the seat.

Arm length: With your arm relaxed at your side, measure from the point of your shoulder to the tip of your middle finger.

Using Stamptivity Bike Fit

Open Stamptivity Bike Fit
Enter your inseam, torso length, arm length, and height
Select your bike type — Road / gravel, Hybrid, or Mountain bike
Read off your starting saddle height, saddle setback range, stem length, and bar reach

Nothing is uploaded — the calculation runs entirely in your browser.

Checking Whether Your Current Setup Fits

Bike Fit isn't only for starting from zero. Add your current saddle height, setback, stem, and crank length, and optionally a short video of yourself pedaling, and the "Does it fit?" panel compares your real setup against the formulas and your video-measured riding position — knee angle, torso angle, and a rough saddle fore-aft read.

It reports a confidence level rather than inventing a precise number to move something by. When the formula and the video disagree, that's shown as a low-confidence conflict for you to judge, not silently resolved.

Mountain Bike & Hybrid Riders

Saddle height (LeMond) and saddle setback (KOPS) are bike-agnostic — they depend on leg length and seated pedaling position, not on what kind of bike you're riding, so they apply the same way on a mountain bike as a road bike.

Stem length and bar reach are different: the formulas are scaled from a drop-bar, road-style position. Select "Mountain bike" or "Hybrid" in the bike-type selector and the calculator flags those two numbers as a rougher proxy rather than a target. Crank length has no sourced target for any bike type in this calculator — and on a mountain bike it also affects pedal-strike clearance on technical terrain, a real concern the tool can't see.

Limitations

This is a starting-point calculator and a rule-based sanity check, not a measured, dynamic fit. A professional fitter accounts for flexibility, riding style, injury history, and pedalling mechanics that formulas from four body measurements cannot see. If you have knee, back, or hip pain, get a professional fit before making large changes to your setup.

Tips

Re-measure if a number looks off. A saddle height that feels far from what a formula suggests is usually a measurement issue (loose shoes, slouched torso) before it's a bad formula.
Change one thing at a time. Move saddle height, then ride a few sessions before touching setback or stem — stacking changes makes it hard to tell what helped.
Film from directly to the side for the video check — an angled camera skews the knee and torso angle readings.
Once your setup is dialed in, use Stamptivity Stamp or Overlay to turn your next ride into a shareable stats image or video.