Dropper Post Length Calculator

Want to know how long of a dropper you can fit on your bike? With two simple measurements our Dropper Post Length Calculator will tell you.

STEP 1 - Measure Dimension X. This is your current saddle height. It is the distance from the top of the seatpost collar to the middle of the saddle rails.

STEP 2 - Measure Dimension Y. This is the your insertion depth. It is the distance from the top of the seatpost collar to an obstruction in your frame. Measure this distance by inserting a rigid post or tape measure into your frame until it hits an obstruction.

Note: Please keep in mind that smooth cable routing away from the dropper actuator is important to proper function. Depending on the frame design, inserting the dropper at the max depth may cause tight/sharp cable routing. Leaving some extra space in the seattube will create a smoother bend in the housing as it transitions from the seattube into the downtube. Once you have your insertion depth, reducing it 10-15mm may be beneficial for your dropper function. 

Note: When the calculator produces a length between the sizes we sell, you'll see brackets below the length suggestion with the actual length dropper you'll need to buy. You'll then shim the post to the suggested length with travel pins supplied with your post purchase. Here is a link to that process: TRAVEL PIN INSTALL

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OneUp Explainer Video

This video explains how to use the OneUp dropper calculator to find the longest dropper post that will fit your bike. You'll learn how to check your dropper diameter and take two key dropper post measurements.

Want a more in-depth description? Access the full-length written guide, How to Know What Dropper Post Fits Your Bike.

Still Need Help?

If you are still having trouble figuring out the right sized dropper post for your bike, reach out to us via the form below. We are here to help and usually respond within 1-2 business days.