How Do I Calculate Current Total Bytes Per Row Used

We are close to exceeding the Maximum Row size of 8K per row and the CIO asked me "how close are we to reaching the 8K row limit?"

I began by looking at byte requirements for the data types we are using
from the systypes table then I wondered, do the indecie, Foreign Keys and Primary Keys use bytes which must be included in my Calculation for current number of bytes used per Row.

Question: How do I calculate Current total number of bytes used per row.