Vampires have been a part of cinema almost since it’s inception. To coincide with the 85th anniversary of Universal Pictures’ ‘Dracula’ starring Bela Lugosi, using fluid dynamics students from the Department of Physics and Astronomy at the University of Leicester have examined how long it would take for the undead fiend to drain an average human’s blood.

They have calculated that it would take only 6.4 minutes to drain 15 per cent of the blood from the external carotid artery in a human’s neck. The human body can’t function during major blood loss. After 15 percent of the blood leaves the body, the heart rate changes, and blood drinking, even from the carotid artery, becomes difficult.

15 per cent was used as the benchmark as any more blood loss causes the heart rate to change, while less can be taken without affecting the circulatory system of a human. Considering the human body has an average of 5 litres of blood and that a vampire might feasibly take 15%, in the study a vampire would drain 0.75 litres of blood, and by their calculations it would take 6.4 minutes to do so.

The students presented their findings in a paper for the Journal of Physics Special Topics, a peer-reviewed student journal run by the University’s department of physics and astronomy.

Course tutor, Dr Mervyn Roy, a lecturer in the University of Leicester’s department of physics and astronomy, said: “Every year we ask each student to write around 10 short papers for the Journal of Physics Special Topics. It lets the students show off their creative side and apply some of physics they know to the weird, the wonderful, or the everyday.”

So if you’re setting out to make a realistic vampire movie, you’ll probably want to give their findings a read.

You can check out the student’s paper in full here.