Our hygrometers come pre-calibrated from the factory with a machine that is much more accurate than your at-home calibration method. Many times, when our customers think that a hygrometer needs calibrated, it is because the humidity is un-even in the humidor. For instance, if you take a hygrometer and set it right on top of the hydro tray, it will read higher, especially if you just started seasoning and haven't put your cigars in yet.The humidity in your humidor will not likely even out completely until it's been half full of cigars after a few weeks. It's important to trust the front hygrometer until that time.With that said, if you'd like to calibrate our hygrometer, here's how you do it:Use your finger to push the hygrometer out of your humidor from the inside.Buy a 75% boveda pack on Amazon.Put the hygrometer and the 75% boveda in a ziplock bag for 12 hours (zipped of course).The hygrometer should read 75%. If not, simply hold the button on the back of the hygrometer for 6 seconds and it will make it read 75%, thus "calibrating" it.Your hygrometer is now ready to be placed back inside your humidor.