Distances and their knowledge of them are an integral part of understanding the interaction between Game Mechanics and Perks in Dead by Daylight.
Map Tiles[]
The Maps in Dead by Daylight are procedurally generated and based on square/rectangular Tiles. The Tiles are more or less fixed in place, but can freely rotate themselves from one iteration to another.
Map Tiles come in three different sizes: 16 by 16, 16 by 32 or 32 by 32 metres.
The shortest and also most accurate and easiest measurable distance in the Game is the length of a border wall section, surrounding the outer boundaries of the Maps. The distance from the centre of one post to the next is exactly 8 metres. On some Maps (ie The Pale Rose), there exists a double wall section, with a length of 16 metres in-between the posts.
Aura-Reading[]
Since most Aura-reading Perks use (partial) increments of 8 in regards to the distance in which they enable the Aura-reading, this makes it simple to gauge the actual in-game distance with the help of the border walls.
Take Sole Survivor for example with 1 Token activated: if the Killer is within 20 metres of you, all their Aura-reading towards you is disabled. This is equivalent to the Killer being within the length of 2 and half border wall sections of you.