is a caliber bigger than a milimeter or vise versa?
A round rated by caliber is not other bigger or smaller than one measured in millimeters they are merely different forms of width. It is complicated because you are dealing with un-equal unit and the millimeter works in together units and the caliber within decimals of 1. A .5 caliber round is far larger than a 5 mm round, but a 20 mm round is FAR larger than a .20 caliber round. As a form of measurement 1 caliber is larger than 1 millimeter as you are comparing 1 tenth of an inch to 1 tenth of a centimeter. A true 1 (1 inch-whole) caliber round would be 25.4 mm. A .177 caliber (BB) is 4.5mm A .22 caliber is around 5.6 mm A 9mm is a .355 caliber A .50 caliber is 12.7mm A 12 measuring device is .729 caliber / 18.5 mm It should be noted that caliber measurements are sometimes slightly different (hundreths and thousandths of an inch) in their actual proportions than they are within name. It is somewhat resembling measuring engine displacement it can be done surrounded by either cubic inch
