SI Base Unit Units
The seven base units of the International System of Units. Since 20 May 2019 each is defined by fixing the numerical value of a constant of nature. 7 units are listed.
| Unit | Symbol | Quantity | Value in SI |
|---|---|---|---|
| Metre | m | Length | Base unit; c = 299,792,458 m/s exactly |
| Kilogram | kg | Mass | Base unit; h = 6.62607015 × 10⁻³⁴ J·s exactly |
| Second | s | Time | Base unit; caesium-133 frequency = 9,192,631,770 Hz exactly |
| Ampere | A | Electric current | Base unit; e = 1.602176634 × 10⁻¹⁹ C exactly |
| Kelvin | K | Temperature | Base unit; k = 1.380649 × 10⁻²³ J/K exactly |
| Mole | mol | Amount of substance | Base unit; Nᴀ = 6.02214076 × 10²³ mol⁻¹ exactly |
| Candela | cd | Luminous intensity | Base unit; Kcd = 683 lm/W at 540 × 10¹² Hz exactly |