short but big shed plans?

Hi, I am having trouble finding a shed to fit my outdoor space. I want to put a shed under my back porch that overhangs my parking pad so as to not take up space where I park but to store my kids toys and bikes and other things. The shed can be no taller than 5 feet with a flat roof or 4 feet with a slanted or pitched roof. I would want the shed to be 6 feet wide and 7 feet deep. Does anyone know of a simple calculator that I can punch these measurements into to find a plan? Whenever I search for calculators like this there are so many more measurements it's asking for and I am by no means a builder but am very well versed in DIY projects and can follow directions well! Thanks in advance!