The answer to this depends on how much protection you require. We recommend a 12 gauge minimum basic security. However, if you require more reliable resistance to torches, saws, and axes, we recommend 10 gauge or thicker.
Also, consider how the body and doors are constructed & measured. For example, is a 1″ door a solid 1″ piece of steel or is it 2 thinner layers of steel with fire insulation in between. Composite doors are common for a variety of reasons, so read through the safe's description and feel free to ask questions.
Most burglars will move-on just at the site of a steel gun safe, but a more sophisticated burglar may have the tools & time to break into a safe. For most people and situations, a 10 - 12 gauge steel safe may be enough security.
Guage to Inches Thickness Guide: