There is actually no ideal size for a home security box. It may depend on the size of the items you intend to store. This detail is very important because it will determine the size and dimensions of the safe that will go perfectly according to your needs.
Also, you have to consider the space where you will be mounting the item. If you have very little space it is best to measure it first so it is easy to choose the right lockbox. However, you should also consider that the smaller the size of the safe is, the easier it is to hide from prying eyes. The standard size of a safe is about 8” x 10” x 10” (height x width x depth).