ปริมาณพื้นฐานต่างๆในระบบ SI
1 ; มีความยาว 1 เมตรThe metre is the iength equal to 1650763.73 wavelength in vacuum of the radiation to the transition between the levels 2p and 5d to krypton-86 atom
2 ; วินาที The second is the duration of 9192631770 periods of the radiation corresponding to the transition between two specific hyperfine levels of the fundamental state of the cesium-133 atom
3 กระแสไฟฟ้า 1A The ampere is the intensity of a constant current which when maintain in two parallel rectilinear conductors of infinite length of negligible cross section and placed at a distance of 1 metre from each other in vacuum would produce between the conductors aforce equal to 2X10 M.K.S units of force per metre length.
4 เคลวิน ( K ) The 10 General Conference of Weights and Measures decided to defined the thermodynamic scale of temperature 273.15 Kelvin exactly
5 แคลเดลลา ( cd ) The candela is the luminous intensity in the perpendicular direction of a surface of 1/600000 m of a black body at the temperature of freezing platinum under a pressure of 101325 newton per square mwtre
6 โมล ( mol ) The mole is an amount of substance of a system which contains as many elementary units as there are carbon atom in 0.012 kg ( exactly ) of C.