EN   EN 
 
 
 EUROPEAN  
COMMISSION   
Brussels, XXX   
[…](2018) XXX  draft  
ANNEX 1  
 
ANNEX  
 
to the  
COMMISSION DIRECTIVE (EU) .../…  
 
 
amending, for the purpose of its adaptation to technical progress, the Annex to Council 
Directive 80/181/EEC as regards the definitions of SI base units  
   
 ANNEX  
In the Annex, Chapter I, section 1. 1 is replaced by the following:  
"1.1. SI base units  
Quantity  Unit 
Name  Symbol  
Length  metre  m 
Mass  kilogram  kg 
Time  second  s 
Electric current  ampère  A 
Thermodynamic temperature  kelvin  K 
Amount of substance  mole  mol 
Luminous intensity  candela  cd 
Definitions of SI base units:  
Unit of length  
 The metre, symbol m, is the SI unit of length. It is defined by taking the fixed 
numerical value of the speed of light in vacuum c to be 299 792 458 when expressed in 
the unit m/s, where the second is defined in terms of ΔvCs. 
Unit of mass  
 The kilogram, s ymbol kg, is the SI unit of mass. It is defined by taking the fixed 
numerical value of the Planck constant h to be 6.626 070 15 x 10-34  when expressed in 
the unit J s, which is equal to kg m2 s-1, where the metre and the second are defined in 
terms of c and ΔvCs. 
 Unit of time  
 The second, symbol s, is the SI unit of time. It is defined by taking the fixed numerical 
value of the caesium frequency ΔvCs, the unperturbed ground -state hyperfine transition 
frequency of the caesium 133 atom, to be 9 192 631 770 when expressed in the unit 
Hz, which is equal to s-1. 
 Unit of electric current  
 The ampere, symbol A, is the SI unit of electric current. It is defined by taking the 
fixed numerical value of the elementary charge e to be 1.602 176 634 x 10-19 when 
expressed in the unit C, which is equal to A s, where the second is defined in terms of 
ΔvCs. 
 Unit of thermodynamic temperature  
 The kelvin, symbol K, is the SI unit of thermodynamic temperature. It is defined by 
taking the fixed numerical value of the Boltzmann constant k to be 1.380 649 x 10-23  
 when expressed in the unit J K-1, which is equal to kg m2 s-2 K-1, where the kilogram, 
metre and second are defined in terms of h, c and ΔvCs. 
 Unit of amount of substance  
(1) The mole, symbol mol, is the SI unit of amount of substance. One mole 
contains exactly 6.022 140 76 x 1023 elementary entities. This number is the 
fixed numerical value of the Avogadro constant, N A,.when expressed in the unit 
mol-1 and is called the Avogadro number.  
The amount of substance, symbol n, of a system is a measure of the number of 
specified elementary entities. An elementary entity may be an atom, a 
molecule, an ion, an electron, any other particle or specified group of particles. 
When the mole is used, the elementary entities must be specified.  
 Unit of luminous intensity  
 The candela, symbol cd, is the SI unit of luminous intensity in a given direction. It is 
defined by taking the fixed numerical value of the luminous efficacy of 
monochromatic radiation of frequency 540 x 1012 Hz, Kcd, to be 683 when expressed 
in the unit Im W-1, which is equal to  cd sr W-1, or cd sr kg-1 m-2  s3, where the 
kilogram, metre and second arc defined in terms of h, c and ΔvCs. 
 1.1.1.  Special name and symbol of the SI derived unit of temperature for 
expressing Celsius temperature  
Quantity  Unit 
Name  Symbol  
Celsius temperature  degree Celsius  °C 
 
Celsius temperature t is defined as the difference t = T – T0 between the two 
thermodynamic temperatures T and T0  where T0  = 273,15 K. An interval or difference 
of temperature may be expressed either in kelvins or in degrees Celsius. The unit 
‘degree Celsius’ is equal to the unit ‘kelvin’."