All rankings are calculated, not measured.
Parameters for calculations include handgun manufacturer's specifications for barrel length, overall length and weight, as well as cartridge ballistics as measured by SAAMI (Sporting Arms and Ammunition Manufacturers' Institute). For a given cartridge there may be a number of bullet weights that are commercially available. We select the typical, or most common cartridge bullet weight commercially available to represent a given caliber.
Caliber specification: typical grain weight and SAAMI measured muzzle velocity
Power Factor (PF)
The Power Factor is a measure of the momentum of the bullet when fired from a particular handgun. It is generated by multiplying the bullet's muzzle velocity times the bullet's mass. (PF = mv x gr). Using bullet mass in grains and muzzle velocity in feet per second the resulting unit of measurement is actually "Grain feet per second" (gr·ft/s).
For defense purposes you want a higher Power Factor.
Recoil Factor (EG)
The Recoil Factor is a measure of the kick-back that a handgun gives you when fired. It is measured in foot-pounds (ft-lb). It relies on the previous specifications and calculations. We use a public domain Standard Free Recoil
equation to calculate recoil.
For defense purposes you want a low Recoil Factor.
Total capacity is the maximum number of cartridges a loaded handgun can hold. For revolvers and derringers this is the number of chambers in the gun. For semi-automatic pistols is is the number of cartridges the gun's standard magazine can hold plus one in the chamber. We do not take into account any extended magazines that a gun may use.
For defense purposes you want a higher Capacity.
While it would be preferable to use all dimensional information to calculate a handgun's relative concealabity (length, width, height, weight), unfortunately only half of the handguns in our database have specifications for width and height. Many manufacturers simply do not provide width and height measurements, and it is often difficult to find that information for older discontinued models in our database. What is ultimately consistent with all handguns we add to the database, at a minimum is overall length and weight. So, we use these two parameters to calculate a relative Concealability factor between guns. The calculation is simply the length in inches plus the weight in pounds (length + (weight/16)). The smaller this number is, the higher the Concealibity factor.
For defense purposes you want a higher Concealability factor.
The Defense Factor is calculated as a derivative sum of the previous four factors. First, each gun's factors are normalized to a percentage value where the highest value of all guns is 100% and the lowest value of all guns is 1%. Once equalized to a percentage they are weighted by an importance scale and summed together: Defense Factor = (Power% * 0.6) + (Capacity% * 0.4) + ((100% - Conceal%) * 0.3) - (Recoil% * 0.3)
Of course, ultimately you want a higher Defense Factor.