2005 city and metro area crime rates per 100,000 population (the most recent comparable final numbers available, released by the FBI in September 2006) for six basic crime categories — murder, rape, robbery, aggravated assault, burglary and motor vehicle theft — were plugged into a formula that measured how a particular city or metro area compared to the national average for a given crime category. The outcome of this equation was then multiplied by a weight assigned to each of the six crime categories. Each of the six crimes was given equal weight. By weighting each crime equally, cities are compared based purely on their crime rates and how they stack up to the national average for a particular crime category. These weighted numbers then were added together for a city or metro area's final score. Finally, these scores were ranked from lowest to highest to determine which cities and metropolitan areas were safest and most dangerous.

While this methodology appears rather complicated, it results in fairer treatment because a city or metro area's crime record is measured against the national average. The farther below the national average, the higher (and better) a city or metro ranked in the final Safest Cities and Metros list; the farther above the national average, the lower (and worse) a city or metro ranked in the final list.