Use this calculator to calculate the volume of concrete needed for a mono pour. In a mono pour you pour the footings and the foundation wall at the same time. It can take a bit more work to put this together but you would save the cost of having a pump truck on site for a second time.
The following images are for use with plywood forms with quick strip ties. The corners are pre made. For an 8" wall the outside corner would be 24" and comes with a matching 16" inside corner. Most common wall heights are anywhere from 2' to 10'. Although you can do mono pours for any heights, using this type of form for a mono type pour after an 8' height would take additional care and time building and pouring the concrete.
To use this calculator you need to provide the length, width, and depth of the footing plus the length, height, and required thickness of the foundation wall. Your measurements should be in feet and inches as required.