Voltage Unit Converter
Convert between any pair of voltage units — volt, millivolt, microvolt, nanovolt, kilovolt, megavolt, gigavolt, statvolt and abvolt — using factors verified against NIST SP 811, the BIPM SI Brochure and ISO 80000-6. Type a value and the result updates instantly.
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What is voltage, and why so many units?
Voltage — formally electric potential difference — is the work done per unit charge to move a positive test charge from one point to another in an electric field. The SI unit is the volt (V), defined as 1 V = 1 W/A = 1 J/C. The volt was named for Alessandro Volta, inventor of the first chemical battery in 1800, and was tied to the SI base units when the International System was formalized after 1948. Because real-world voltages span more than fifteen orders of magnitude — from the microvolt-level signal of a thermocouple to the gigavolt potentials inside a lightning bolt — engineers use SI prefixes (milli-, micro-, nano-, kilo-, mega-, giga-) to keep numbers in a comfortable range.
The volt is by far the dominant unit in modern engineering, but two CGS units survive in physics literature: the statvolt (≈299.79 V), from the electrostatic system, and the abvolt (10⁻⁸ V), from the electromagnetic system. They appear in older textbooks on electromagnetism and in some theoretical physics papers; you will not encounter them on a multimeter. The SI volt is the only unit any electrical or electronics technician needs day-to-day.
The voltage units, explained
Volt (V) and its multiples — the SI baseline
1 V = 1 J/C = 1 W/A = 1 kg·m²·s⁻³·A⁻¹. Since the 2019 SI redefinition the volt is realized through the elementary charge e and the Planck constant h, both fixed exactly. Practical multiples are the millivolt (mV, 10⁻³ V), microvolt (μV, 10⁻⁶ V), nanovolt (nV, 10⁻⁹ V), kilovolt (kV, 10³ V), megavolt (MV, 10⁶ V), and gigavolt (GV, 10⁹ V). Each is the same physical quantity scaled by a power-of-ten prefix.
Millivolt (mV) and microvolt (μV) — sensors, biosignals
1 mV = 10⁻³ V; 1 μV = 10⁻⁶ V. Thermocouples produce 40 μV/°C (K-type), so a 100 °C temperature difference yields about 4 mV. Biopotential signals — EEG (10–100 μV), ECG (≈1 mV), EMG (50 μV–10 mV) — sit in the millivolt and microvolt range. Op-amp input offset voltages are typically 1–5 mV, the limit of small-signal precision.
Nanovolt (nV) — low-noise instrumentation
1 nV = 10⁻⁹ V. Used in nanovoltmeters, SQUID magnetometers and reference Josephson junctions. The Johnson noise of a 1 kΩ resistor at room temperature in a 1 Hz bandwidth is about 4 nV — this is the absolute floor for analog electronics.
Kilovolt (kV) — power transmission
1 kV = 1000 V. Distribution networks run at 11 kV, 22 kV, and 33 kV in cities; sub-transmission at 66 kV and 110 kV; long-distance transmission at 220 kV, 400 kV, 500 kV, 765 kV. EV fast-chargers operate at 400 V or 800 V (technically <1 kV but commonly grouped). Industrial X-ray tubes and CRT acceleration voltages range 30–150 kV.
Megavolt (MV) — HVDC and physics
1 MV = 10⁶ V. Ultra-high-voltage HVDC links run at ±800 kV (1.6 MV between poles) — the Changji–Guquan link in China is rated ±1.1 MV. Particle accelerator electrostatic injectors (Pelletron, Tandem) can reach 25 MV. Lightning channels in a strong storm carry transient voltages near 100 MV between cloud and ground.
Statvolt and abvolt — CGS legacy units
1 statV = c × 10⁻⁸ V = 299.792458 V exactly (where c is the speed of light in cm/s). 1 abV = 10⁻⁸ V. The statvolt belongs to the electrostatic CGS system and the abvolt to the electromagnetic CGS system. They were designed to make Maxwell's equations dimensionally simpler in CGS, but at the cost of unit ratios involving c. They appear in classical textbooks (Jackson's Classical Electrodynamics) and some plasma physics papers, but no commercial instrument has been calibrated in CGS units in decades.
Real-world voltages and which unit to expect
- Household electricity: United States and Canada: 120 V (single phase) and 240 V (split phase, used for stoves and dryers). European Union, UK, Vietnam, Australia: 230 V (±10% per IEC 60038). Japan: 100 V at 50 or 60 Hz. India, much of Africa: 230 V.
- Consumer electronics: USB charger (USB 2.0): 5 V at 0.5–2 A. USB-C PD: 5 V, 9 V, 15 V, 20 V, 28 V, 36 V, 48 V (negotiated). Laptop barrel-jack adapters: typically 12–20 V. Smartphone battery: 3.7 V nominal (Li-ion). LED desk lamp 12 V or 24 V.
- Automotive: Standard car battery: 12 V nominal (12.6 V fully charged, 11.8 V deeply discharged). Heavy-duty truck/bus: 24 V. Mild hybrid: 48 V auxiliary system. Battery-electric and plug-in hybrid: 400 V (Tesla, VW MEB, most Asian EVs); 800 V (Porsche Taycan, Hyundai E-GMP, Lucid Air) for faster DC charging.
- Power transmission: Distribution feeders: 11 kV, 22 kV, 33 kV. Transmission: 110 kV, 220 kV, 400 kV, 500 kV, 765 kV. HVDC: ±320 kV up to ±800 kV (and ±1.1 MV in China). Substation transformers step down through these levels to deliver 230/120 V to homes.
- Biomedical signals: EEG (brain electrical activity): 10–100 μV. ECG (heart): around 1 mV peak (R-wave). EMG (muscle): 50 μV–10 mV. Action potential of a neuron: ≈70 mV (resting) to +30 mV (peak depolarization). All measured with high-input-impedance amplifiers.
- Lightning and atmospheric: Cloud-to-ground lightning: about 100 MV potential difference, carrying 30 kA peak current for tens of microseconds. Static electricity on a person walking on carpet: 5–20 kV (tiny charge, harmless beyond a tingle).
- Photovoltaic and battery storage: A single Si PV cell: 0.6 V open-circuit. A 60-cell module: 36 V open-circuit. Modern utility-scale PV strings: 1500 V DC. Tesla Megapack: ~1500 V DC battery bus. Home Powerwall: 50 V DC nominal.
How much is 1 unit of each in volts?
| Unit | Value in volts (V) |
|---|---|
| 1 V (Volt) | 1 Pa |
| 1 mV (Millivolt) | 0.001 Pa |
| 1 μV (Microvolt) | 0.000001 Pa |
| 1 nV (Nanovolt) | 0.000000001 Pa |
| 1 kV (Kilovolt) | 1000 Pa |
| 1 MV (Megavolt) | 1000000 Pa |
| 1 GV (Gigavolt) | 1000000000 Pa |
| 1 statV (Statvolt (CGS-ESU)) | 299.792458 Pa |
| 1 abV (Abvolt (CGS-EMU)) | 0.00000001 Pa |
Frequently asked questions about voltage units
How do I convert between any two voltage units?
Multiply by the source unit's volt-factor and divide by the target's. Example: 5000 mV to V → 5000 × 0.001 ÷ 1 = 5 V. The converter above does this in real time with double-precision arithmetic.
What's the difference between AC and DC voltage?
Direct current (DC) voltage has constant polarity — battery + on top, − on bottom, always. Alternating current (AC) voltage reverses polarity periodically (50 or 60 times per second on the grid). When we say '230 V AC' we mean the RMS (root-mean-square) value; the peak voltage is √2 × 230 = 325 V, and the peak-to-peak is 650 V. A multimeter set to AC measures RMS by default.
What is the household voltage in different countries?
United States and Canada: 120 V / 60 Hz. European Union, UK, Vietnam, Australia, India: 230 V / 50 Hz (UK historically 240 V, now harmonized). Japan: 100 V (50 Hz east, 60 Hz west). Brazil: mix — São Paulo 127 V, Brasília 220 V, depends on the state. Mexico: 127 V.
Why is USB always 5 V?
USB 1.0 (1996) defined 5 V because that matched the TTL logic supply of the time, and ports could safely supply 100–500 mA without dedicated regulation. USB Power Delivery (PD), introduced in 2012 and widely adopted by 2020, negotiates higher voltages — 9, 15, 20, 28, 36, 48 V — to deliver up to 240 W to laptops while keeping current manageable.
What does 'rated voltage' mean on appliances?
Rated voltage is the nominal supply voltage at which the device is designed to operate. A '230 V' appliance must work safely from about 207 V to 253 V (±10% per IEC 60038). Plugging a 120 V US appliance into a 230 V European outlet without a transformer typically destroys it within seconds because power scales with V².
Is voltage dangerous?
Voltage by itself is not dangerous — the current it can drive through your body is. The danger threshold is around 30 V AC or 60 V DC if your skin is dry; below that, healthy skin resistance limits current to safe levels. Above 50 V AC or 120 V DC any contact is potentially lethal. High-frequency RF can also produce burns at lower voltages.
What is a typical car battery voltage?
A 12 V lead-acid car battery measures 12.6 V fully charged at rest, drops to about 12.0 V at 50% state of charge, and 11.8 V is considered deeply discharged. While the engine runs, the alternator regulates the bus to about 13.8–14.4 V to charge the battery. Heavy-duty trucks use 24 V (two 12 V batteries in series).
Why do EVs use 400 V or 800 V?
Higher voltage means lower current for the same power, which means thinner cables and smaller losses. A 400 V system delivering 250 kW needs 625 A; an 800 V system delivers the same 250 kW at 312 A. The 800 V architectures (Porsche Taycan, Hyundai Ioniq 5/6, Kia EV6) charge from 10% to 80% in about 18 minutes at 350 kW DC fast chargers, half the time of a 400 V car.
What is the voltage of a lightning strike?
A typical cloud-to-ground lightning strike develops about 100 MV potential difference between cloud base and ground, drives 30 kA peak current, and lasts ~30 μs. Total energy is 1–5 GJ but discharged so quickly that the average power during the strike is over 1 TW. Surge protectors clamp building-side spikes to the kV range so equipment survives.
Can I link to a specific conversion?
Yes. The URL updates as you change units and value, so you can copy the address bar after any conversion. Example: ?from=V&to=mV&x=12.
References
Dedicated converter pages
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