Voltage Converter — Convert Between All Electrical Voltage Units
Our free voltage converter instantly converts between microvolts (µV), millivolts (mV), volts (V), kilovolts (kV), and megavolts (MV). Whether you're an electrical engineer working with power systems, a student studying circuit theory, or a hobbyist building electronics projects, this tool provides accurate conversions with the formulas and context you need to understand voltage relationships.
What Is Voltage?
Voltage, formally known as electric potential difference, is the work needed to move a unit of electric charge between two points in an electric field. Named after Italian physicist Alessandro Volta (inventor of the first chemical battery in 1800), voltage is measured in volts (V) and represents the "pressure" that drives electric current through a conductor.
In practical terms, voltage is the energy per coulomb of charge. One volt means one joule of energy per coulomb of charge (1 V = 1 J/C). Without voltage difference, no current flows — just as water won't flow without pressure difference. Higher voltage means more force pushing electrons through a circuit.
Voltage Units and Prefixes
The SI unit of voltage is the volt (V), with standard metric prefixes applied for different scales:
Microvolt (µV) = 0.000001 V: Used for biological signals (EEG brain waves: 5-100 µV, nerve signals: 70-100 µV), precision sensor outputs, and radio frequency signal levels. Measuring microvolts requires shielded equipment due to ambient electrical noise.
Millivolt (mV) = 0.001 V: Common in thermocouple measurements (0-50 mV), ECG heart signals (1-5 mV), solar cell individual outputs, and analog sensor readings. Many industrial instruments operate in the millivolt range.
Volt (V): The standard unit for everyday electricity. Batteries (1.5V, 3.7V, 9V, 12V), household outlets (110V-240V), and most consumer electronics operate in the volt range. USB provides 5V, laptop chargers typically 19-20V.
Kilovolt (kV) = 1,000 V: Used in power distribution (11kV-33kV residential feeders, 66kV-132kV sub-transmission), electric vehicle battery packs (400V-800V approaching 1kV), and industrial equipment. High-voltage warning signs typically start at 1kV.
Megavolt (MV) = 1,000,000 V: Found in lightning (100-300 MV), long-distance power transmission (up to 1.1 MV in China's UHV lines), particle physics accelerators, and Van de Graaff generators used in research.
Ohm's Law and Voltage Relationships
Ohm's law is the fundamental equation of electrical circuits: V = I × R, where V is voltage (volts), I is current (amperes), and R is resistance (ohms). This relationship means:
If you know any two values, you can calculate the third. A 12V battery driving current through a 4Ω resistor produces 3A of current (I = V/R = 12/4 = 3). This same law applies at every scale — from microvolts in neural circuits to megavolts in power transmission.
Power (watts) relates to voltage through P = V × I or equivalentlyP = V²/R. This is why power lines use high voltage — transmitting 1 MW at 500 kV requires only 2A of current, allowing thin wires with minimal resistive losses. The same power at 240V would require 4,167A, demanding impossibly thick conductors.
World Voltage Standards
Global mains voltage standards fall into two main families, reflecting historical decisions made in the early electrification era:
110-120V at 60Hz: Used in North America (USA, Canada, Mexico), Japan (both 50Hz and 60Hz regions), parts of South America, and some Caribbean nations. This standard was established by Thomas Edison's early DC systems and later adapted for AC. The lower voltage was considered safer but requires thicker wires for the same power delivery.
220-240V at 50Hz: Used in Europe, UK, Australia, most of Asia, Africa, and South America. This standard emerged from German engineering tradition and was adopted widely during colonization. Higher voltage means more efficient power delivery with thinner conductors, reducing copper costs in wiring.
When traveling internationally, voltage converters (transformers) or dual-voltage devices are essential. Plugging a 120V device into a 240V outlet without a converter will likely damage or destroy the device. Modern electronics (laptops, phone chargers) typically accept 100-240V automatically via switching power supplies.
Electrical Safety and Voltage
The danger of electrical shock depends on voltage, current through the body, current path, duration, and skin resistance. Dry skin has 100,000+ ohms resistance, while wet skin drops to 1,000 ohms or less. General safety thresholds:
Below 50V AC / 120V DC is generally considered "extra-low voltage" (ELV) and safe under normal conditions. Between 50V-1000V AC is "low voltage" (despite the name, it's dangerous). Above 1000V AC is "high voltage" requiring specialized training and equipment. However, current as low as 10mA through the heart can be fatal — and at 240V with wet skin (1000Ω), Ohm's law gives 240mA, far exceeding lethal levels.
Always de-energize circuits before working on them, use properly rated test equipment, and respect voltage ratings on insulation and components. Arc flash hazards at high voltages can cause severe burns even without direct contact.
Common Voltage Conversion Examples
Battery voltages: AA battery = 1.5V = 1,500mV. Lithium-ion cell = 3.7V = 3,700mV. Car battery = 12V = 0.012kV. Electric vehicle pack = 400V = 0.4kV.
Household: US outlet = 120V = 120,000mV. European outlet = 230V = 0.23kV. Electric dryer/stove (US) = 240V = 0.24kV.
Power grid: Residential distribution = 11kV = 11,000V. Transmission line = 400kV = 0.4MV. Ultra-high voltage line = 1,100kV = 1.1MV.
Frequently Asked Questions
What is voltage?
Voltage is the electric potential difference between two points — the "pressure" that drives electric current through a circuit. It's measured in volts (V) and represents the energy per unit charge (1 volt = 1 joule per coulomb).
How many millivolts are in a volt?
There are exactly 1,000 millivolts (mV) in one volt (V). The prefix "milli-" means one-thousandth, so 1 mV = 0.001 V. Similarly, 1 microvolt (µV) = 0.000001 V.
Why do some countries use 110V and others 220V?
It's historical. The US standardized on 110V (later 120V) during early electrification with Edison's systems. Europe adopted 220V (later 230V) for efficiency — higher voltage allows thinner wires for the same power. Both are safe with proper installation.
What is Ohm's law?
Ohm's law states V = I × R (Voltage = Current × Resistance). It's the fundamental relationship in electrical circuits. Knowing any two values lets you calculate the third.
What voltage is dangerous?
Generally, voltages above 50V AC or 120V DC are considered dangerous. However, danger depends on current, path through the body, duration, and skin condition. Wet conditions significantly increase risk even at lower voltages.
What is a kilovolt used for?
Kilovolts (kV) measure high voltages in power distribution lines (11-33kV), industrial equipment, X-ray machines (40-150kV), and electric vehicle battery systems (400-800V). Power transmission uses hundreds of kV for efficiency.
How does voltage relate to power?
Power (watts) = Voltage × Current (P = V × I). Higher voltage allows the same power to be delivered with less current, which is why power lines use high voltage — less current means less energy lost as heat in the wires.
What generates voltage in nature?
Natural voltage sources include lightning (100-300 million volts), electric eels (up to 860V), static electricity (thousands of volts at very low current), piezoelectric crystals under pressure, and thermoelectric effects from temperature differences.