I really don't care if my TM-1 is calibrated or not. When I bought it, I checked the readings of the only "professionally" built wheels I've ever owned. I then built my wheels using that value. After 5 or 6 sets of wheels, I just check the value on the ones already built and use that number for my next set. I couldn't tell you Kgf on any of my wheels. But, I rarely break spokes and my wheels stay true.