Concrete Sidewalk

[Concrete Dummy]

Hi,
I will be pouring a concrete sidewalk/patio slab and need to know how much concrete I need.
I did my own calculations, but do not trust them.
Here is what I am building (Broken down into measurable squares)
All are measured in inches and will be a 4" slab/sidewalk
1: 36" x 96"
2: 91" x 89"
3: 43" x 44"
4: 90" x 45"

I would like to know how much this converts into for a 4 inch slab/sidewalk and how much it converts into Cubic Feet.
Like I said, I did my own calculations but do not trust them before purchasing the concrete.
Thank you,
Concrete Dummy

[kurtk]

where ever you decide to get the concrete from will tell you how many yards you will need ,with those measurements

[Guest]

I multiplied those dimensions by 4" then divided by 1728 cu in/cu ft. I get:
1: 8.0 cu ft
2: 18.75 cu ft
3: 4.38 cu ft
4: 9.38 cu ft

Total: 40.5 cu ft = 1.5 cu yd