Oct 2025
SI units system
Basic units of the SI system
| Quantity |
Name |
Symbol |
| Length |
Meter |
m |
| Mass |
kilogram |
kg |
| Time |
Second |
s |
| Electric current |
Ampere |
A |
| Thermodynamic temperature |
Kelvin |
K |
| Luminous intensity |
Candela |
cd |
| Amount of substance |
Mole |
mol |
Derived SI units:
| Quantity |
Name |
Symbol |
Defining equation |
| Frequency |
Hertz |
Hz |
1 Hz = 1 s-¹ = 1/s |
| Force |
Newton |
N |
1 N = 1 kg·m/s² |
| Pressure and mechanical stress |
Pascal |
Pa |
1 Pa = 1 N/m² |
| Work (energy, heat) |
Joule |
J |
1 J = 1 N·m = 1 W·s |
| Power, energy flow, heat flow |
Watt |
W |
1 W = 1 N·m/s = J/s |
| Electrical charge, quantity of electricity |
Coulomb |
C |
1 C = 1 A·s |
| Electrical potential, potential difference (voltage) |
Volt |
V |
1 V = 1 W/A |
| Electric capacitance |
Farad |
F |
1 F = 1 A·s/V |
| Impedance |
Ohm |
O |
1 O = 1 V/A |
| Electrical conductivity |
Siemens |
S |
1 S = 1 O-¹ = 1 A/V |
| 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 = 1 V·s/A |
| Luminous flux |
Lumen |
lm |
1 lm = 1 cd·sr |
| Illumination |
Lux |
lx |
1 lx = 1 lm/m² |
| Plane angle |
Radian |
rad |
1 rad = 1 m/m = 1 = 180°/p |
| Solid angle |
Steradian |
sr |
1 sr = 1 m²/m² = 1 |