@Keet
I agree that a rough percentage would be a more accurate calculation but that would force every author to keep track of the percentage while writing or work through it after completion.
It's not a matter of being more accurate. It's more flexible. Your original one sex scene per chapter driven conception doesn't work at all for long chapters or stories without chapters.
I don't consider 39% still in the some sex category. More like under 25%.
Yeah, where you draw the lines is heavily driven by personal preferences.
where do you draw the line between what is considered graphic and what not
I'll agree that where you draw the line is heavily driven by personal opinion and perception.
Here's how I draw that line:
If you are painting a picture of the sex with words, describing the action well enough for me to visualize the sex scene from your description, that's graphic.
If I have to make that image up entirely from my own imagination, that's not graphic.