Josephson constant = 483 597.848 4... × 109 Hz·V⁻¹

Value
483 597.848 4... × 109
Unit
Hz·V⁻¹
Uncertainty
exact (by definition)
Copy-ready
483597.8484e9

The Josephson constant K_J = 2e/h: the frequency-to-voltage ratio of a Josephson junction.

Exact since 2019, it is how national labs realise the volt — an array of junctions driven at a known microwave frequency.

NIST, Fundamental Physical Constants — Complete Listing (2022 CODATA adjustment), retrieved 2026-07-26.

Electrical, thermal and X-ray constants

Angstrom starConductance quantumCopper x unitElectron charge to mass quotientFermi coupling constantFirst radiation constantHartree energyJosephson constantLattice parameter of siliconLattice spacing of ideal Si (220)Loschmidt constant (273.15 K, 101.325 kPa)Magnetic flux quantumMolar mass constantMolar mass of carbon-12Molar Planck constantMolar volume of siliconMolybdenum x unitNeutron-proton mass differenceProton charge to mass quotientQuantum of circulationSackur-Tetrode constant (1 K, 101.325 kPa)Second radiation constantVon Klitzing constantWeak mixing angleWien frequency displacement law constantW to Z mass ratio

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All physical constants

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