This soil texture calculator is built specifically for use with our Garden Tutor soil texture testing jar kit available here
For those that like math:
Measure the thickness of each layer and the entire sample. Divide the thickness of each layer by the thickness of the entire sample. Multiply each result by 100, and you will have the rough percentages of sand, silt, and clay that comprise your soil. Match your results to the chart to find out your soil texture type.
For example: if your sand layer is 20 16ths of an inch thick and the entire sample is 38 16ths thick, divide 20 by 38 to get .526 then multiply this by 100 to get 52.6%