SI Units Studio: Master Table, Prefix Visualizer & Converter

Unit Name	Symbol	Quantity	Breakdown	Type
Meter	m	Length	m	Base
Kilogram	kg	Mass	kg	Base
Second	s	Time	s	Base
Ampere	A	Electric Current	A	Base
Kelvin	K	Thermodynamic Temperature	K	Base
Mole	mol	Amount of Substance	mol	Base
Candela	cd	Luminous Intensity	cd	Base
Hertz	Hz	Frequency	s⁻¹	Derived
Newton	N	Force	kg⋅m⋅s⁻²	Derived
Pascal	Pa	Pressure	kg⋅m⁻¹⋅s⁻²	Derived
Joule	J	Energy, Work	kg⋅m²⋅s⁻²	Derived
Watt	W	Power	kg⋅m²⋅s⁻³	Derived
Coulomb	C	Electric Charge	A⋅s	Derived
Volt	V	Voltage	kg⋅m²⋅s⁻³⋅A⁻¹	Derived
Farad	F	Capacitance	kg⁻¹⋅m⁻²⋅s⁴⋅A²	Derived
Ohm	Ω	Resistance	kg⋅m²⋅s⁻³⋅A⁻²	Derived
Siemens	S	Conductance	kg⁻¹⋅m⁻²⋅s³⋅A²	Derived
Weber	Wb	Magnetic Flux	kg⋅m²⋅s⁻²⋅A⁻¹	Derived
Tesla	T	Magnetic Flux Density	kg⋅s⁻²⋅A⁻¹	Derived
Henry	H	Inductance	kg⋅m²⋅s⁻²⋅A⁻²	Derived
Lumen	lm	Luminous Flux	cd⋅sr	Derived
Lux	lx	Illuminance	cd⋅sr⋅m⁻²	Derived
Becquerel	Bq	Radioactivity	s⁻¹	Derived
Gray	Gy	Absorbed Dose	m²⋅s⁻²	Derived
Sievert	Sv	Equivalent Dose	m²⋅s⁻²	Derived
Katal	kat	Catalytic Activity	mol⋅s⁻¹	Derived

The Language of the Universe

Imagine trying to build a rocket where one team measures in inches and another in millimeters. It leads to disaster (as NASA famously found out). The International System of Units (SI) solves this by providing a single, coherent standard for measurement used by every country in the world (with a few stubborn exceptions).

The 2019 Revolution

For over a century, the Kilogram was defined by a physical metal cylinder locked in a vault in Paris. If that cylinder got scratched, the definition of a kilogram changed for the entire universe!

In 2019, scientists redefined the SI system. Now, every unit is based on Fundamental Constants of Nature—numbers that are woven into the fabric of reality, like the Speed of Light and the Planck Constant. We no longer need artifacts; we use the laws of physics themselves as our ruler.

Why Metric Wins

The beauty of SI (Metric) is its base-10 simplicity. To switch from meters to kilometers, you just move a decimal point.

Compare this to the Imperial system: 12 inches in a foot, 3 feet in a yard, 1760 yards in a mile. The cognitive load of these arbitrary conversion factors slows down engineering and science. SI streamlines calculation, reducing errors and making science accessible.

Deconstructing Derived Units

All physical reality can be described using just 7 Base Units. Every other unit is a "Derived Unit"—a combination of the bases.

Take the Volt. It feels like a fundamental concept, right? But physically, 1 Volt is the potential difference required to move 1 Ampere of current against 1 Watt of power. When you break it down further, a Volt is actually:
kg · m² · s⁻³ · A⁻¹

Our Unit Deconstructor tool above helps you visualize these hidden relationships, showing you exactly what "one Newton" or "one Pascal" is actually made of.

The Scale of Reality (Prefixes)

Science deals with the unimaginably large and the infinitesimally small. To handle this, we use Prefixes.

Tera (10¹²) to Exa (10¹⁸): The scale of computing data and astronomical distances.
Nano (10⁻⁹): The scale of molecules and computer chips.
Femto (10⁻¹⁵): The scale of atomic nuclei.

In 2022, four new prefixes were added to the extremes: Ronna/Quetta for the massive, and Ronto/Quecto for the tiny, ensuring SI is ready for the future of quantum computing and data science.

Frequently Asked Questions

What are the 7 SI Base Units?

The 7 fundamental units are: Meter (Length), Kilogram (Mass), Second (Time), Ampere (Electric Current), Kelvin (Temperature), Mole (Amount of Substance), and Candela (Luminous Intensity). All other units are derived from these.

What changed in the 2019 SI Redefinition?

In 2019, the SI system was redefined so that all base units are based on fixed fundamental constants of nature (like the speed of light or Planck constant) rather than physical artifacts. The 'Le Grand K' prototype kilogram was retired.

What is the difference between specific weight and mass?

Mass (kg) is the amount of matter in an object and is constant everywhere in the universe. Weight (N) is the force of gravity acting on that mass. A 10kg object has the same mass on the Moon, but weighs much less.

Why uses Kelvin instead of Celsius in Physics?

Kelvin is an absolute scale starting at Absolute Zero (0 K), where all thermal motion stops. This makes thermodynamic equations much simpler compared to Celsius, which has an arbitrary zero point (freezing water).

What are Derived Units?

Derived units are combinations of base units used to measure other quantities. For example, Speed is Length/Time (m/s), and Force is Mass × Acceleration (kg·m/s²), which is named the Newton.

What is the smallest Metric Prefix?

As of 2022, the smallest official prefix is Quecto- (10⁻³⁰). The largest is Quetta- (10³⁰). These were added to accommodate data science and quantum physics needs.

Why defines the Second?

Since 1967, the Second is defined by the vibrations of a Cesium-133 atom. Specifically, it is the duration of 9,192,631,770 periods of radiation corresponding to the transition between two hyperfine levels of the ground state.

Is the Liter an SI unit?

Technically, no. The SI unit for volume is the cubic meter (m³). However, the Liter (L) is accepted for use with SI units because it is a convenient size (1/1000th of a m³).

What is a Dimensionless Quantity?

A quantity that has no physical dimension, usually appearing as a ratio. Examples include angles (radians), refractive index, and friction coefficients.

How do I convert between prefixes?

Moving 'up' the scale (e.g., mm to m) requires dividing by factors of 10. Moving 'down' (e.g., km to m) requires multiplying. Our 'Prefix Scale' visualizer helps map these relationships vertically.