Von Klitzing Constant

The resistance quantum of the quantum Hall effect: 25,812.807 Ω, the world's ohm standard.

Specifications & Metrics

symbol

RK

status

Exact — exact via h and e in the 2019 SI

value

25812.80745 ohm

Relative Scale in Constants

Core Principles & Analysis

• Exactly h/e², and the Hall resistance of the plateau measures it in integer fractions.
• Klaus von Klitzing discovered the effect in 1980 and took the 1985 Nobel Prize.
• Graphene's room-temperature quantum Hall effect keeps improving the measurement.