Jun 20, 2016 · Once the total load weight is determined, a safety factor should be added to the total. We recommend adding a 33% addition to the total weight of the load for safety. So, for a 4-wheeled cart that weights 3,000 lbs., the safety factor would equal 3,990 lbs. Dividing this weight by 4 gives a caster with a rating of 1,000 lbs per caster, which is