"the length of which" is correct and commonly used in written English.
It is typically used to refer to the length of something previously mentioned in the sentence. Example: "I walked along the river, admiring the majestic trees lining its banks. The length of which seemed to stretch on for miles."
His punctuality does not extend into the off-season, however, the length of which varies depending on whether you ask the team or Ramirez.
A temporary disability program also provides some pay for women on maternity leave, the length of which is determined by a doctor.
Lewis Black still cherishes a phone call of support he received from Carlin during Black's own apprenticeship, the length of which he calls "staggering".
No one can question the sacrifice she has made, the things she has had to forgo during her fast, the length of which is utterly unprecedented.
At the end of the series — the length of which has yet to be determined — Lens will publish a PDF of the images in sequence.
Livy began by composing and publishing in units of five books, the length of which was determined by the size of the ancient papyrus roll.
There were also a diaulos, two lengths, and a dolichos, or long-distance race, the length of which varied and might have been as much as 24 stades, or nearly 3 miles (4.8 km).
Colonel Paul directed that Mr. Qosi remain in Camp Four for 60 days while the military worked out where he would serve the rest of his sentence, the length of which is in a sealed portion of the plea deal.
On canalized rivers navigation is facilitated by constructing locks that create a series of steps, the length of which depends on the natural gradient of the valley and on the rise at each lock.
In this period the tanka almost completely ousted the chōka, the length of which was indefinite, because the shorter tanka were more suited to the lover's billet-doux or to competitions on prescribed themes.
The months are alternately 30 and 29 days long except for the 12th, Dhū al-Ḥijjah, the length of which is varied in a 30-year cycle intended to keep the calendar in step with the true phases of the moon.
