Voltage Converter

Convert between different voltage units

Voltage Converter
Common Voltage References

Household & Electronics

AA Battery: 1.5V
USB: 5V
Car Battery: 12V
US Household: 120V
EU Household: 230V

High Voltage

Power Lines: 11-33kV
Transmission: 110-800kV
Lightning: ~100MV
Static Electricity: 1-25kV

Complete Voltage Conversion Guide

Comprehensive guide to voltage measurements, conversions, and electrical engineering applications

Understanding Voltage Units

Voltage Unit Scale

  • •Microvolt (μV) = 0.000001 V — used for sensor signals
  • •Millivolt (mV) = 0.001 V — thermocouples, small sensors
  • •Volt (V) — SI base unit of electric potential
  • •Kilovolt (kV) = 1,000 V — power transmission, X-ray tubes
  • •Megavolt (MV) = 1,000,000 V — lightning, particle accelerators

Key Voltage References

  • •AA battery: 1.5 V DC
  • •Car battery: 12 V DC
  • •USB 2.0/3.0: 5 V DC
  • •Household US: 120 V AC RMS (170 V peak)
  • •Household EU/UK: 230 V AC RMS (325 V peak)
  • •High-voltage transmission: 100–765 kV
  • •EV battery pack: 400–800 V DC

Voltage Conversion Reference

DC Voltage Conversions

  • •1 V = 1,000 mV
  • •1 kV = 1,000 V
  • •1 MV = 1,000 kV
  • •1 mV = 1,000 μV
  • •1 GV = 1,000 MV
  • •1 V = 0.001 kV

AC Voltage Relationships

  • •RMS = Peak ÷ √2 (≈ Peak × 0.7071)
  • •Peak = RMS × √2 (≈ RMS × 1.4142)
  • •Peak-to-peak = 2 × Peak
  • •120 V RMS → 170 V peak → 340 V peak-to-peak
  • •230 V RMS → 325 V peak → 650 V peak-to-peak

Ohm's Law & Power

  • •V = I × R (Voltage = Current × Resistance)
  • •V = P / I (Voltage = Power / Current)
  • •V = √(P × R)
  • •Power (W) = V² / R
  • •Power (W) = V × I

Professional Applications

Consumer Electronics

  • •USB charging: 5 V (USB-A), 9/12/20 V (USB-C PD)
  • •HDMI: up to 5 V signal
  • •LVDS displays: 1.2–1.8 V
  • •Logic levels: 3.3 V and 5 V (TTL)
  • •Audio line level: ±0.7 V peak
  • •Lithium battery cell: 3.0–4.2 V

Industrial & Power Systems

  • •Single-phase supply: 120 V (US) / 230 V (EU)
  • •Three-phase supply: 208/240 V (US) / 400 V (EU)
  • •Motor drives: 240/480 V
  • •Control circuits: 24 V DC
  • •PLC I/O: 24 V DC or 120 V AC
  • •Substation secondary: 4.16–34.5 kV
  • •Transmission: 69–765 kV

Medical & Instrumentation

  • •ECG signal: 0.5–4 mV amplitude
  • •EEG signal: 10–100 μV
  • •Thermocouple output: 0–60 mV
  • •4–20 mA loop with 250 Ω load: 1–5 V
  • •Defibrillator charge: 200–360 J at ~5 kV
  • •MRI gradient coils: up to 1,000 V
  • •pH electrode: ±0.5 V

Power Transmission & Renewable Energy

  • •Distribution: 4–35 kV
  • •Sub-transmission: 26–69 kV
  • •HV transmission: 115–230 kV
  • •EHV transmission: 345–765 kV
  • •UHV: above 1,000 kV (China, India)
  • •Solar panel string: 300–600 V DC
  • •Wind turbine output: 690 V (typical)

Voltage Measurement Best Practices

Safety First

  • •Always use properly rated test equipment (CAT rating)
  • •Never exceed meter CAT rating for the circuit being measured
  • •Use insulated probes and gloves for high-voltage work
  • •De-energize before connecting or disconnecting leads
  • •Verify meter is functioning before measuring live circuits
  • •OSHA 70E arc flash requirements apply above 50 V

Measurement Accuracy

  • •Allow capacitors to fully discharge before measuring DC
  • •Use true-RMS meters for non-sinusoidal AC waveforms
  • •Use differential probes for floating circuits
  • •Account for probe loading effects at high impedance nodes
  • •Calibrate against a known reference before critical measurements
  • •Ground loops can cause significant measurement errors

Voltage Examples by Category

Batteries & DC Sources

  • •AA alkaline: 1.5 V
  • •9 V block: 9 V
  • •Car 12 V lead-acid: 12.6 V (full charge)
  • •Laptop battery: 10.8–14.4 V
  • •EV Tesla Model 3: ~350 V nominal
  • •18650 Li-ion cell: 3.7 V nominal
  • •Solar panel (36 cell): ~18 V open circuit

AC Mains & Grid

  • •US household: 120 V / 60 Hz
  • •EU household: 230 V / 50 Hz
  • •UK household: 230 V / 50 Hz
  • •US three-phase: 208 V line-to-line
  • •US industrial: 480 V three-phase
  • •EU industrial: 400 V three-phase
  • •Japan: 100 V / 50–60 Hz

Electronics & Signals

  • •TTL logic high: 2.4–5 V
  • •CMOS 3.3 V logic: 3.3 V
  • •USB 2.0: 5 V ±5%
  • •USB-C PD max: 48 V
  • •RS-232 signal: ±3 to ±15 V
  • •Ethernet (PoE): 44–57 V
  • •HDMI 2.1 DDC: 5 V

Frequently Asked Questions

What is the difference between AC and DC voltage?▾
DC (direct current) voltage is constant and flows in one direction — like a battery's 1.5 V or a car's 12 V. AC (alternating current) voltage reverses polarity at the grid frequency (60 Hz in the US, 50 Hz in Europe). The 120 V or 230 V listed for wall outlets is an RMS value, which represents the equivalent heating power; the actual voltage swings from positive to negative peak continuously.
What is RMS voltage?▾
RMS (Root Mean Square) voltage is the effective value of an AC voltage — the DC equivalent that would deliver the same power to a resistive load. For a pure sine wave, RMS = Peak ÷ √2 ≈ 0.7071 × Peak. So a US outlet at 120 V RMS has a peak of about 170 V and a peak-to-peak swing of 340 V.
Why is US voltage 120 V and Europe 230 V?▾
The US standardized on 110–120 V early in the electric age, when lower voltage was considered safer and motors/bulbs of the era were designed for it. Europe and most of the world later adopted 220–240 V because higher voltage transmits the same power at lower current, reducing resistive losses and allowing thinner, cheaper wiring. The two standards became entrenched before global harmonization was practical.
How do I safely measure high voltage?▾
Use a multimeter or probe rated for the voltage category (CAT III or CAT IV for power distribution). Always connect the ground lead first and the live lead last; disconnect in reverse order. Wear insulated gloves rated for the voltage level, use one hand where possible to prevent current across the chest, and never work alone on live high-voltage circuits. Follow NFPA 70E or your local equivalent for arc flash protection above 50 V.
What does CAT rating mean on a multimeter?▾
CAT ratings (Category I through IV) indicate the transient overvoltage a meter can safely withstand. CAT I is for protected electronic circuits; CAT II for household appliances; CAT III for fixed building wiring, distribution panels, and motors; CAT IV for utility service entrances and outdoor conductors. Always use a meter rated at or above the category of the circuit you are measuring.
How does voltage relate to current and power?▾
Ohm's Law states V = I × R: voltage equals current (amperes) times resistance (ohms). Power in watts is P = V × I = V² / R = I² × R. Doubling voltage while keeping resistance constant quadruples power, which is why high-voltage transmission lines deliver the same power at much lower current — reducing I²R losses dramatically over long distances.