This calculator will estimate the materials cost of your new shed. Labor cost is not included as it assumes you are building your shed yourself. It assumes also a typical rectangular shaped shed. If you are building a shed that's attached to a wall of your house or other building, you can substract 25% of the walls cost although this won't be very precise (building attached shed may require a bit more beams).
I have pre-defined some material costs that will roughly help you if you don't know the real material costs in your area. Still, it's much better to research the actual prices instead of using the pre-defined ones.
The calculator will figure out the areas of the foundation and walls and will add up the roof costs and finishing costs to come up with a grand total.