Personally, I wouldn't get all worked up over calibration. We're usually trying to see how heavy a gun is. Measurment to the nearest ounce is all I can envision is required. I expect any digital scale could do that. But for those that 'gots to know', take a one gallon jug of water to the post office, UPS or FedEx store(they all have periodic calibration of their scales) and have them weigh it for you and mark the jug. Keep the sealed jug around for a "calibration weight".