ConstantID

Inverse of conductance quantum

ElectromagneticExact

G0−1 = 12 906.403 72… Ω

Value
12 906.403 72… Ω
Standard uncertainty
exact
Relative uncertainty
exact
Status
Exact since the 2019 SI redefinition
Symbol
G0−1
Source
CODATA 2022 via NIST · NIST entry

NIST prints this exact value cut to 10 digits. ConstantID recomputes it from the defining constants: 12 906.403 729 652 253 330 022 758 353…

Use in a calculation

# inverse of conductance quantum, CODATA 2022 (NIST)
inverse_of_conductance_quantum = 1.2906403729652253330022758353043722e4  # ohm, exact

# SciPy: scipy.constants.physical_constants['inverse of conductance quantum']

What it is

The resistance of a single perfect conduction channel for electrons, counting both spin directions: h/2e², about 12.9 kΩ. Exact since 2019.

It is built only from constants that have exact values since 20 May 2019, so it is exact too; CODATA 2018 was the first adjustment to list it that way.

How the value changed, 1998–2022

Each point is one CODATA adjustment, plotted as its difference from the 2022 value; the bars show one standard uncertainty (an arrowhead means the bar runs off the chart). Diamonds mark adjustments in which the value was exact.

inverse of conductance quantum: CODATA values 1998–2022 relative to the 2022 value, in parts per trillion, with one-standard-uncertainty bars−1000−5000+500+1000parts per trillion1998200220062010201420182022

Relative uncertainty

inverse of conductance quantum: relative standard uncertainty in each CODATA adjustment, logarithmic scale10⁻¹¹10⁻¹⁰10⁻⁹199820022006201020142018exact2022exact
CODATAValue (uncertainty)Relative uncertaintyChange from previous
202212 906.403 72…exact exact
201812 906.403 72…exact −2.7 σ of 2014
201412 906.403 7278(29)2.2 × 10−10 +1.5 σ of 2010
201012 906.403 7217(42)3.3 × 10−10

“Change from previous” is the shift in the value divided by the standard uncertainty of the previous adjustment. Earlier values are converted into the current unit where NIST changed it (for example J s to J Hz⁻¹).