International System of Units

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International System of Units

International system of unit (SI) and its usage. Excerpt from JIS Z 8203:2000

1. Scope of application
This standard defines the international system of unit (SI), recommends use of some
specifically-selected units for general use from among units in the table for integral
power of ten units, further specifies other units that may be used with the SI and
provides the definition of SI basic unit.

2. Reference standards
Standards listed below constitute the provisions of this standard by being referenced
herein. The latest version of the reference standards applies.
IEC 27-1: 1971, Letter symbols to be used in electrical technology - Part 1: General

3. SI unit The name international system of unit(SI)and its internationally-used abbreviation"SI"
were officially adopted in the 11th CGPM (Conference General des Poides et Mesures) in 1960.
This unit system consists of the following units to constitute a consistent unit system.
- Basic units
- Derived units

3.1 Basic units
There are 7 basic international units as indicated in Table 1.

● Table 1 SI basic units

Basic amount
SI basic units
Name
Symbol
Length
m
m
Mass
kg
kg
Time
Second
s
Current
Ampere
A
Thermodynamic
temperature
Kelvin
K
Substance
quantity
Mol
mol
Brightness
Candela
cd


 

● Table 2 SI derived units with specific names

Derived amount
SI derived units
Specific name Symbol
Indications by SI basic units
and SI derived units
Plane angle
Radian
rad 1rad=1m/m=1
Solid angle
Steradian
sr 1sr=1m2/m2=1
Frequency
Herz
Hz 1 Hz=1 s-1
Force
Newton
N 1 N=1 kg・m/s2
Pressure and stress
Pascal
Pa 1 Pa=1 N/m2
Energy, work and heat quantity
Joule
J 1 J=1 N・m
Power and flux
Watt
W 1 W=1 J/s
Charge and electric quantity
Coulomb
C 1 C=1 A・s
Electric potential, electric
potential difference, voltage
and electromotive force
Bolt
V 1 V=1 W/A
Capacitance
Farad
F 1 F=1 C/V
Electric resistance
Ohm
Ω 1 Ω=1 V/A
Conductance
Siemens
S 1 S=1 Ω-1
Magnetic flux
Weber
Wb 1 Wb=1 V・s
Magnetic flux density
Tesla
T 1 T=1 Wb/m2
Inductance
Henry
H 1 H=1 Wb/A
Celsius temperature
Celsius degree* t ℃=t+273.15 K
Beam
Lumen
lm 1 lm=1 cd・sr
Illuminance
Lux
lx 1 lx=1lm/m2

*Celsius degree is a specific name that replaces the Kelvin unit to indicate the Celsius temperature value.


● Table 3 SI derived units with specific names appreciated to protect human health

Derived amount
SI derived units
Specific name
Symbol
Indications by SI
basic units and SI
derived units
Radioactivity
(of radionuclide)
Becquerel
Bq 1 Bq=1 S-1
Absorbed dose mass
energy allocation,
kerma, absorbed
dose rate
Gray
Gy 1 Gy=1 J/kg
Dose equivalent
Sievert
Sv 1 Sv=1 J/kg


 

● Table 4 SI prefix

Multiples
applied to
unit
Prefix
Name Symbol
1024 Yotta Y
1021 Zetta Z
1018 Exa E
1015 Peta P
1012 Tera T
109 Giga G
106 Mega M
103 Kilo k
102 Hecto h
10 Deca da
10-1 Deci d
10-2 Centi c
10-3 Milli m
10-6 Micro μ
10-9 Nano n
10-12 Pico p
10-15 Femto f
10-18 Atto a
10-21 Zepto z
10-24 Yocto y

Table of conversion rate to primary SI units

Force N dyn kgf
1
1×10-5
9.806 65
1×105
1
9.806 65×105
1.019 72×10-1
1.019 72×10-6
1

Viscosity
Pa・s cP P
1
1×10-3
1×10-1
1×103
1
1×102
1×10
1×10-2
1

● 1 P= 1 dyn・s/cm2= 1 g/cm・s, 1 Pa・s= 1 N・s/m2, 1 cP= 1 mPa・s


 
Stress
Pa or N/m2 MPa or N/mm2 kgf/mm2 kgf/cm2
1
1×106
9.806 65×106
9.806 65×104
1×10-6
1
9.806 65
9.806 65×10-2
1.019 72×10-7
1.019 72×10-1
1
1×10-2
1.019 72×10-5
1.019 72×10
1×102
1

● 1 Pa= 1 N/m2, 1 MPa= 1 N/mm2



 
Kinetic
viscosity
m2/s cSt St
1
1×10-6
1×10-4
1×106
1
1×102
1×104
1×10-2
1

● 1 St= 1 cm2/s, 1 cSt= 1 mm2/s


 
Pressure
Pa kPa MPa bar kgf/cm2 atm mmH2O mmHg or Torr
1
1×103
1×106
1×105
9.806 65×104
1.013 25×105
9.806 65
1.333 22×102
1×10-3
1
1×103
1×102
9.806 65×10
1.013 25×102
9.806 65×10-3
1.333 22×10-1
1×10-6
1×10-3
1
1×10-1
9.806 65×10-2
1.013 25×10-1
9.806 65×10-6
1.333 22×10-4
1×10-5
1×10-2
1×10
1
9.806 65×10-1
1.013 25
9.806 65×10-5
1.333 22×10-3
1.019 72×10-5
1.019 72×10-2
1.019 72×10
1.019 72
1
1.033 23
1×10-4
1.359 51×10-3
9.869 23×10-6
9.869 23×10-3
9.869 23
9.869 23×10-1
9.678 41×10-1
1
9.678 41×10-5
1.315 79×10-3
1.019 72×10-1
1.019 72×102
1.019 72×105
1.019 72×104
1×104
1.033 23×104
1
1.359 51×10
7.500 62×10-3
7.500 62
7.500 62×103
7.500 62×102
7.355 59×102
7.600 00×102
7.355 59×10-2
1

● 1 Pa= 1 N/m2


 
Work, energy and
heat quantity
J kW・h kgf・m kcal
1
3.600 ×106
9.806 65
4.186 05×103
2.777 78×10-7
1
2.724 07×10-6
1.162 79×10-3
1.019 72×10-1
3.670 98×105
1
4.268 58×102
2.388 89×10-4
8.600 0×102
2.342 70×10-3
1

● 1 J= 1 W・s, 1 J= 1 N・m

Power (advantage and
power) heat current
W kgf・m/s PS kcal/h
1
9.806 65
7.355 ×102
1.162 79
1.019 72×10-1
1
7.5 ×10
1.185 72×10-1
1.359 62×10-3
1.333 33×10-2
1
1.580 95×10-3
8.600 0×10-1
8.433 71
6.325 29×102
1

● 1 W= 1 J/s, PS:French horse-power


 
Heat thermal
conductivity
W/(m・k) kcal/(h・m・℃)
1
1.162 79
8.600 0×10-1
1

 

Thermal
conductivity factor
W(m2・K) kcal/(h・m2・℃)
1
1.162 79
8.600 0×10-1
1

 

Specific heat
J/(kg・K) kcal/(kg・℃)
cal/(g・℃)
1
4.186 05×103
2.388 89×10-4
1


 


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