Common equity vs preferred equity for calculating net debt

How does one calculate preferred equity?
On one website it says Preferred equity = stockholders equity - common equity
another website says common equity = stockholders equity - preferred shares

This implies that preferred equity = stockholders equity - (stockholders equity - preferred shares) = preferred shares

This doesn't make sense to me. Preferred shares... is this preferred shares outstanding? I think its a mistake.

Given that stockholders equity is total assets - total liabilities, If I had to guess... I would guess that preferred equity = stockholders equity * preferred shares outstanding / (preferred shares outstanding + common shares outstanding)

Anyway, not sure. The reason I need it is because I have this formula for net debt which I am trying to use to calculate enterprise value :
Net debt = short term debt + long term debt + portion of long term debt due in 1 year + convertible debt amount outstanding + minority non controlling interest + preferred equity- cash and cash equivalents - convertible preferred equity amount outstanding

Thanks