Or remove it and measure the links (don't forget the magic link).
When brand new, the chain should be a whole number of inches, just multiply by two to get the number of links. If it is worn it will be slightly longer, but not long enough to take it up to the next inch on your tape measure.
TABLE OF CONTENTS Bottom Bracket & Sizing Chain & Chain Ring Specifications Related Spare Parts & Accessories Bottom Bracket & Sizing All Rocky Mountain Powerplay models are designed for optimum user experience, both on and off the bike....
One way is to measure a new chain against the old one and shorten if necessary (assuming the new chain is at least as long as the old one)
Assuming you haven't changed anything, I 'd recommend trying getting a 126 link chain and being prepared to shorten it by a couple of links - you'll need a chain splitter tool.