Date Published:Jun. 18. 2015
International System of Units
International System of Units
International system of unit (SI) and its usage. Excerpt from JIS Z 8000-1:2014
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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