Voltage Conversion Calculator
Written by Thierno Sadou Diallo, formula verified per our methodology • Last checked on 9/10/2026
To convert a voltage, it is reduced to volts (V), then converted into the desired unit. Example: a mains voltage of 230 V equals 230,000 mV.
Explanation
The volt (V), the SI unit of voltage (or potential difference), measures the energy transferred per unit of charge between two points of a circuit. Its prefixes follow the same decimal rules as the other electrical units: the millivolt and microvolt are used for very low-amplitude signals (a sensor, a biomedical signal such as an electrocardiogram, on the order of a millivolt), the volt for common voltages (batteries, domestic mains at 230 V in France, 120 V in North America), and the kilovolt or megavolt for high-voltage power transmission lines. This calculator converts between these scales using the volt as the pivot unit. To calculate a voltage from resistance and current rather than converting a known value, see our Ohm's law calculator, and for the related quantity, our electric current conversion calculator.
Example: a mains voltage of 230 V
Inputs
Value: 230. Starting unit: V. Target unit: mV.
Calculation
The "milli" prefix means 0.001: to go from volts to millivolts, multiply by 1,000. 230 × 1,000 = 230,000 mV.
Result
A voltage of 230 V equals 230,000 mV.
Frequently asked questions
Why is a sensor's voltage often expressed in millivolts?
Because many sensors (thermocouples, biomedical sensors) produce very low-amplitude electrical signals, generally from a few millivolts to a few tens of millivolts — expressing these values in volts would mean handling very small, hard-to-read decimal numbers.
What is the mains voltage in France?
In France, as in most of the European Union, the nominal domestic mains voltage is 230 V (single-phase), with a tolerance of ±10% allowed by the standard.
How do you calculate a voltage rather than convert it?
This calculator converts a known voltage value between units; to calculate a voltage from other electrical quantities (resistance and current), use instead our Ohm's law calculator, which directly applies the relationship V = R × I.
Do other electrical quantities also have their own prefixes to convert?
Yes: see our electric current conversion calculator for current, or our electrical resistance conversion calculator for resistance, each with its usual orders of magnitude.