'''Knot efficiency''' describes how much a knot weakens a rope, compared to how strong a rope is without the knot, expressed as a percentage.  When a knotted rope is [[tensile testing|pulled to the point of failure]], the rope will always fail at the knot.

Whenever there is a stress concentration in a rope, that stress concentration weakens the rope.  Stress concentrations allow stress failures to begin at that point.

Knots known for having a high knot effiency:
* [[Clove hitch]], and its derivatives.

[[Splicing]] tends to have a knot effiency of ~85%, higher than any knot.[citation needed]

Certain ropework practices try to maximize the knot efficiency as much as possible:
* [[Tensile testing]], where the knot efficiency of the grips needs to be >= 100%.
* [[Wire rope]] [[rope termination|terminations]], such as is used in cranes and ship towing operations.