What is a volt in simple terms?

A volt is the unit that measures electric potential difference, often called voltage. One volt is the difference in potential that moves one joule of energy per coulomb of charge. It can be thought of as the electrical pressure that pushes current through a circuit.

Is a volt the same as an amp?

No. A volt measures electric potential difference (the push), while an ampere measures electric current (the flow of charge). They are related by Ohm's law: voltage equals current multiplied by resistance.

How many volts are in a standard wall outlet?

Household mains voltage is about 120 volts in North America and roughly 230 volts across most of Europe, Asia, Africa, and Australia. Both are alternating current at 50 or 60 hertz.

How many volts is dangerous to humans?

Both voltage and current matter, but voltages above roughly 50 volts can drive enough current through the body to be hazardous. Standard household voltages of 120 V and 230 V are capable of causing fatal shocks.

What is the formula for a volt?

One volt equals one joule per coulomb (1 V = 1 J/C), or equivalently one watt per ampere (1 V = 1 W/A). In SI base units, a volt is kilogram metre squared per ampere second cubed.

What Is a Volt? Definition, Ohm's Law & Examples

Definition

A volt (symbol: V) is the SI unit of electric potential, electric potential difference, and electromotive force — the quantity commonly called voltage. It measures the difference in electric potential energy per unit of charge between two points in a circuit.

The volt is defined as one joule of energy per coulomb of charge, which is also equal to one watt per ampere:

1 V = 1 J/C = 1 W/A

Expressed in SI base units, the volt is kilogram metre squared per ampere second cubed:

1 V = 1 kg·m²·A−¹·s−³

A helpful way to picture voltage is as electrical pressure. Just as water pressure pushes water through a pipe, voltage is the force that pushes electric charge through a conductor. A higher voltage means a stronger push, and therefore more potential energy delivered per unit of charge.

Ohm's Law

The volt sits at the centre of Ohm's law, the most fundamental relationship in electrical work. It links voltage (V), current in amperes (I), and resistance in ohms (R):

V = I × R

This single equation can be rearranged to solve for any of the three quantities: current is I = V ÷ R, and resistance is R = V ÷ I.

Worked example: A circuit carries a current of 2 amperes through a resistor of 6 ohms. The voltage across the resistor is V = I × R = 2 A × 6 Ω = 12 volts. If the resistance were doubled to 12 ohms while the current stayed at 2 A, the voltage would rise to 24 V — more electrical pressure is required to drive the same current through greater resistance.

Everyday Examples

Voltage spans an enormous range, from the tiny signals inside electronics to the high-tension lines that span continents. The table below lists familiar reference points.

Source	Typical Voltage
Nerve signal in the human body	~0.07 V (70 mV)
AA / AAA alkaline battery	1.5 V
Lithium-ion cell (single)	3.7 V
USB power	5 V
Car battery	12 V
Household mains (North America)	120 V
Household mains (Europe / Asia)	230 V
Electric vehicle battery pack	400–800 V
Local distribution power lines	4,000–35,000 V
High-voltage transmission lines	110,000–765,000 V

Common Multiples

Because voltages range across many orders of magnitude, standard SI prefixes are used to keep numbers manageable. The most common multiples and submultiples of the volt are shown below.

Name	Symbol	Value	Typical Use
Microvolt	µV	0.000001 V (10⁻⁶ V)	Sensor and antenna signals
Millivolt	mV	0.001 V (10⁻³ V)	Thermocouples, ECG signals
Volt	V	1 V	Batteries, electronics
Kilovolt	kV	1,000 V (10³ V)	Power distribution, X-ray tubes
Megavolt	MV	1,000,000 V (10⁶ V)	Transmission grids, lightning

History

The volt is named after Alessandro Volta (1745–1827), the Italian physicist who in 1800 invented the voltaic pile — the first device capable of delivering a steady electric current. By stacking alternating discs of zinc and copper separated by brine-soaked cloth, Volta produced a continuous source of electricity, proving that current could come from chemistry rather than from friction or living tissue. His work laid the groundwork for the entire field of electrochemistry and electrical engineering.

The unit was formally adopted to honour Volta and was defined in its modern form as part of the International System of Units (SI). Today the volt is realised with extraordinary precision through the Josephson effect, a quantum phenomenon that ties voltage to fundamental physical constants, allowing national metrology laboratories to reproduce the volt identically anywhere in the world.

Need to switch between microvolts, millivolts, kilovolts, and more? Use our voltage converter for fast, precise results.