Converting Feet/inches To Decimal Equivalent

I am new to Excel but not programming and I am looking for a recommendation for the following. I have a spreadsheet that simply takes the length and width of an area and computes the square feet and yardage and other sundry items. I am entering the feet/inches as follows:

Example: 11.3 (equals 11/ft 3/inches)

The correct decimal conversion should be 11.25 but, obviously, it does not know that the number to the right of the decimal point is an indicator of inches. (ex.: .5=.42, .7=.58, .9=.75, .11=.92)

I have approached this from the stand point of an IF condition, finding the position of the "." and grabbing everything to the right (+1) but I understand that the limitation is 7 nested IFs.

Can someone get me kick-started on what the best approach would be to get my entry to convert to the true decimal equivalent? Currently, I am simply doing the conversion from memory but I would rather automate this sometimes errant approach.