Open Access

Table 2

Impact of new definitions of the SI base units.

Unit Constant used as reference Symbol Actual definition Proposed definition
kg Mass of prototype kilogram m (K) Exact 1.0 × 10−8
Planck constant h 5.0 × 10−8 Exact
A Vacuum magnetic permeability µ 0 Exact 2.3 × 10−10
Elementary charge e 2.5 × 10−8 Exact
K Temperature of triple point of water T TPW Exact 3.7 × 10−7
Boltzmann constant k B 1.7 × 10−6 Exact
mol Molar mass of 12C M (12C) Exact 4.5 × 10−10
Avogadro number N A 1.4 × 10−9 Exact

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