What safety factor should I use for a rimless aquarium?
For standard rimmed aquariums, a safety factor of 3.8 is the industry standard. For rimless aquariums, because the top edge is completely unsupported, you should use a minimum safety factor of 3.8, but 4.0 to 4.2 is highly recommended to prevent bowing and catastrophic failure.
Annealed vs Tempered Glass
This calculator assumes standard annealed float glass. Tempered glass is much stronger, but cannot be drilled or cut after tempering. Most custom DIY builds use standard annealed glass for the sides, as it flexes slightly before breaking, whereas tempered glass shatters instantly if stressed.