Areas for an Architectural project

Hi, Please help, Maths is not my strong point.
I am doing an Architectural project to design a self storage unit (not very glamorous!). I have an overall structure size with fire escapes and access doors into which I have to insert as many storage areas of pre-determined areas as possible while keeping fire escape routes and accesses clear.
If I have the storage area sizes and one dimension for the space, how can I establish what the other dimension is to produce a space of that known area. IE I have to create a space with an area of 13.935m2 (150SqFt) and I have one dimension of 4m. What calculation can be used to give the other dimension?
Thanks
Marcaw

Sorry, you want a rectangle of area $13.935 m^2$ such that one side is of length $4m$? Do you know the formula for the area of a rectangle?

Simply put.... Yes and yes (length x width).