Though there are many free freight class calculators available online, they can be misleading in certain of cases. Often, the NMFC code they generate is based solely on dimensions, weight, density, and value. But, these are not the only factors that matter. An over-reliance on these calculators can lead to costly reclassification charges. Three additional factors determine shipping class: Stowability, Handling, and Liability, and it is important to keep them in mind as well: