SI Units: List and Conversion Table (International System of Units)

2026/05/07

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SI base units

Quantity Base unit Definition
Symbol Name
Time Second s The second [s] is a unit of time. Its magnitude is defined by setting the value of the hyperfine transition frequency ΔνCs of a cesium-133 atom in its ground state to exactly 9192631770, expressed in units of s⁻¹ (equivalent to Hz).
Length Meter m The meter [m] is a unit of length. Its value is defined in terms of the unit m·s⁻¹ by fixing the numerical value of the speed of light in a vacuum, c, to exactly 299,792,458.
Mass kilogram kg The kilogram [kg] is a unit of mass. Its value is defined in terms of the unit s⁻¹·m²·kg (equivalent to J·s) by fixing the value of Planck’s constant h to 6.62607015×10⁻³⁴.
Electric current Ampere A The ampere [A] is the unit of electric current. Its magnitude is defined by fixing the value of the elementary charge e to 1.602176634×10⁻¹⁹. The unit is the coulomb, which is also equal to A·s.
Thermodynamic temperature Kelvin K The kelvin [K] is the unit of thermodynamic temperature. Its magnitude is defined by fixing the value of the Boltzmann constant k to 1.380649×10⁻²³, expressed in terms of the unit s⁻²·m²·kg⁻¹ (equivalent to J·K⁻¹).
Amount of substance Mole mol The mole [mol] is the unit of amount of substance. One mole contains exactly 6.02214076×10²³ elementary particles. This value, expressed in units of mol⁻¹, is the fixed value of Avogadro's number NA and is known as Avogadro's number.
Luminous intensity Candela cd The candela [cd] is the unit of luminous intensity. Its magnitude is defined in terms of the units s³·m⁻²·kg⁻¹·cd·sr or cd·sr·W⁻¹ (equivalent to lm·W⁻¹) by setting the luminous efficiency of monochromatic light of frequency 540 × 10¹² Hz to 683.

A consistent set of SI derived units represented by specific names and symbols

Assembly volume Name Symbol Expression in
other SI units		 Expression in SI base
units
Angle Radian rad 1 m/m
Solid angle Steradian sr 1 m²/m²
Frequency Hertz (Hz) Hz s1
Force Newton N m·kg·s⁻²
Pressure and stress Pascal (Pa) Pa N/m² m⁻¹·kg·s⁻²
Energy, Work, and Heat Joule (joule) J N·m m²·kg·s⁻²
Power, Work Rate, Radiant Flux Watt W J/s m²·kg·s⁻³
Electric charge Coulomb C s·A
Potential difference (voltage) / Electromotive force Volt (V) V W/A m²·kg·s⁻³·A⁻¹
Capacitance Farad F C/V m⁻²·kg⁻¹·s⁴·A²
Electrical resistance Ohm (ohm) Ω V/A m²·kg·s⁻³·A⁻²
Conductance Siemens (siemens) S A/V m⁻²·kg⁻¹·s³·A²
Magnetic flux Weber (Wb) Wb V·s m²·kg·s⁻²·A⁻¹
Magnetic flux density Tesla (tesla) T Wb/m² kg·s⁻²·A⁻¹
Inductance Henry (henry) H Wb/A m²·kg·s⁻²·A⁻²
Celsius Celsius °C K
Luminous flux Lumen (lumen) lm cd·sr cd·m²/m² = cd
Illuminance Lux (lux) lx lm/m² m⁻²·cd
Radioactivity of a radionuclide Becquerel (Bq) Bq s⁻¹
Absorbed dose, specific energy distribution, and karma Gray (Gray) Gy J/kg m²·s⁻²
Dose equivalent, ambient dose equivalent, directional dose equivalent, personal dose equivalent Sievert Sv J/kg m²·s⁻²
Enzyme activity Katal kat s⁻¹·mol

SI prefix

Multiplier Name Symbol Decimal Notation Multiplier Name Symbol Decimal Notation
101 Dec da 10 10⁻¹ deci d 0.1
102 hecto h 100 10⁻² centimeters C 0.01
103 kilograms k 1000 10⁻³ millimeters m 0.001
106 Mega M 1,000,000 10⁻⁶ Micro μ 0.000001
109 Giga G 1000000000 10⁻⁹ Nano n 0.000000001
10¹² tera T 1000000000000 10⁻¹² Pico p 0.000000000001
10¹⁵ Peta P 1000000000000000 10⁻¹⁵ Femto f 0.000000000000001
10¹⁸ Exa E 1000000000000000000 10⁻¹⁸ Atto a 0.000000000000000001
1021 Zeta Z 1000000000000000000000 10⁻²¹ Zepto z 0.000000000000000000001
1024 Yota Y 1000000000000000000000000 10⁻²⁴ Yoct y 0.000000000000000000000001

Conversion Table for Major SI Units

Strength

N dyn kgf
1 1×10⁵ 1.01972×10⁻¹
1×10⁻⁵ 1 1.01972×10⁻⁶
9.80665 9.80665×10⁵ 1

Stress

Pa or N/m² MPa or N/mm² kgf/mm² kgf/cm²
1 1×10⁻⁶ 1.01972×10⁻⁷ 1.01972×10⁻⁵
1×10⁶ 1 1.01972×10⁻¹ 1.01972×10
9.80665×10⁶ 9.80665 1 1×10²
9.80665×10⁴ 9.80665×10⁻² 1×10⁻² 1

*1 Pa = 1 N/m², 1 MPa = 1 N/mm²

Pressure

Pa kPa MPa bar kgf/cm² atm mmH₂O mmHg or Torr
1 1×10⁻³ 1×10⁻⁶ 1×10⁻⁵ 1.01972×10⁻⁵ 9.86923×10⁻⁶ 1.01972×10⁻¹ 7.50062×10⁻³
1×10⁻³ 1 1×10⁻³ 1×10⁻² 1.01972×10⁻² 9.86923×10⁻³ 1.01972×10² 7.50062
1×10⁶ 1×10³ 1 1×10 1.01972×10 9.86923 1.01972×10⁵ 7.50062×10³
1×10⁵ 1×10² 1×10⁻¹ 1 1.01972 9.86923×10⁻¹ 1.01972×10⁴ 7.50062×10²
9.80665×10⁴ 9.80665×10 9.80665×10⁻² 9.80665×10⁻¹ 1 9.67841×10⁻¹ 1×10⁴ 7.35559×10²
1.01325×10⁵ 1.01325×10² 1.01325×10⁻¹ 1.01325 1.03323 1 1.03323×10⁴ 7.60000×10²
9.80665 9.80665×10⁻³ 9.80665×10⁻⁶ 9.80665×10⁻⁵ 1×10⁻⁴ 9.67841×10⁻⁵ 1 7.35559×10⁻²
1.33322×10² 1.33322×10⁻¹ 1.33322×10⁻⁴ 1.33322×10⁻³ 1.35951×10⁻³ 1.31579×10⁻³ 1.35951×10 1

*1 Pa = 1 N/m²

Work, Energy, Passion

J kW·h kgf·m kcal
1 2.77778×10⁻⁷ 1.01972×10⁻¹ 2.38889×10⁻⁴
3.600×10⁶ 1 3.67098×10⁵ 8.6000×10²
9.80665 2.72407×10⁻⁶ 1 2.34270×10⁻³
4.18605×10³ 1.16279×10⁻³ 4.26858×10² 1

*1 J = 1 W·s, 1 J = 1 N·m

Work rate (mechanical rate, power) heat flux

W kgf·m/s PS kcal/h
1 1.01972×10⁻¹ 1.35962×10⁻³ 8.6000×10⁻¹
9.80665 1 1.33333×10⁻² 8.43371
7.355×10² 7.5×10 1 6.32529×10²
1.16279 1.18572×10⁻¹ 1.58095×10⁻³ 1

*1 W = 1 J/s; Note: French horsepower

Viscosity

Pa・s pCp P
1 1×10³ 1×10
1×10³ 1 1×10⁻²
1×10⁻¹ 1×10² 1

*1 P = 1 dyn·s/cm² = 1 g/cm·s; 1 Pa·s = 1 N·s/m²; 1 cP = 1 mPa·s

Kinematic viscosity

m/s cSt St
1 1×10⁶ 1×10⁴
1×10⁻⁶ 1 1×10⁻²
1×10⁻⁴ 1×10² 1

*1 St = 1 cm²/s, 1 cSt = 1 mm²/s

Thermal conductivity

W/(m·K) kcal/(h·m·°C)
1 8.6000×10⁻¹
1.16279 1

Thermal conductivity

W (m²·K) kcal/(h·m²·°C)
1 8.6000×10⁻¹
1.16279 1

Specific heat

J/(kg·K) kcal/(kg·°C)
cal/(g·°C)
1 2.38889×10⁻⁴
4.18605×10³ 1

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