What size of rental trailer is right for me? Quite simply, different people are going to have different size loads when they are moving. Getting a trailer that’s too small could result in having to make multiple trips. Having a trailer that’s too large can result in items moving around and being damaged. It also has wasted space and expenses. To determine your size of trailer, go through the house room by room. Make a note of everything that is being moved, including the expected boxes. From there, online calculators can help estimate the size and weight of the expected move. This will allow the rental of the correct size of trailer for the move.