It can be measured arbitrarily by the repulsive odour emitted and the texture of the pussy; whether there is a coarse forest around the entrance, which absorbs sweat and malodorous fumes. It can also be known as "the pong that repels the dong"
Clagg also accounts for many unfortunate encounters with male tongues, where to many a regret, the tongue recoils in horror at being swamped with a brillo pad of hairs and that tangy fishy taste, like licking a battery made from rotten mackerel carcasses, whilst it pumps out a noxious gas like stale chicken soup.
It denotes the level of moisture, humidity, unclean sweat, multiplied by the thickness and density of pubes, combined with variable dubious discharge or vaginal crumbs, taken to the power of covering clothing. The thicker the layers, the less the pussy can breathe. Thick leggings with knickers underneath can amplify the clagg factor.
Refer to the "Whiff to Weave" ratio, whereby a looser weave will allow passage of such fumes into the atmosphere, contributing to global warming, but saving one from a dodgy cunt with concentrated odours resulting from a tight knit.
Also, the number of times the girl has been roasted by random guys adds to the CLAGG ratio, as does looseness of the pussy. Soggy beef curtains and a shitload of pubes is a lethal mix.
As my grandad used to say... "Son - The Dirtier the Slag, Beware of The Clagg"
No one likes a claggy mott....