Voltage Converter

This converts a voltage from any one unit into all the others at once. The volt is the SI unit of electric potential difference, and like current it is met far more often in its prefixed forms than on its own. Millivolts appear in sensor outputs, thermocouples and audio line levels. Microvolts appear in low-noise measurement and biopotential signals such as an ECG. Kilovolts appear in transmission and distribution, and in New Zealand the network you connect to is typically 400 volts three phase or 230 volts single phase at the point of supply, with 11 kV and above upstream of it. The relationships are all exact powers of ten defined by the SI prefix system rather than measured ratios, so nothing is lost converting between them. The reason a converter is worth having is that datasheets and meters disagree about which unit to use, and a figure written as 0.0025 V is far easier to misread than the same figure written as 2.5 mV. Scientific notation is shown as well, since that is how very small potentials are usually printed, and negative values work normally because voltage is a difference and has a sign.

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1,000 mV
in millivolts
Volts1
Microvolts1,000,000
Kilovolts0.001
Megavolts0.000001
Scientific1.0000e+0 V

SI prefixes are exact powers of ten, so the conversion introduces no rounding of its own. Very large or very small results switch to scientific notation.

How it works

Every unit is converted to volts first, then out to the target. The factors are exact: 1 MV is 1,000,000 V, 1 kV is 1,000 V, 1 mV is 0.001 V and 1 uV is 0.000001 V. Because these are definitions rather than measurements, converting from millivolts to volts and back returns exactly the number you started with. The only rounding you will see is in the display.

Worked example

Take the default of 1 volt. In millivolts that is 1 x 1,000 = 1,000 mV, and in microvolts 1 x 1,000,000 = 1,000,000 uV. Going upward, 1 V is 0.001 kV. A practical case: a type K thermocouple produces roughly 0.0000405 V per degree Celsius near room temperature. Entered as volts that reads 40.5 uV per degree, which is the figure you would actually compare against the input range of an amplifier.

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Data sources: unit definitions follow the International System of Units (SI), in which the prefixes are exact powers of ten.

Frequently asked questions

How many millivolts are in a volt?

Exactly 1,000. The prefix milli means one thousandth, so 1 mV is 0.001 V. This is an SI definition rather than a measured conversion, so no rounding error is introduced either way.

What voltage is mains power in New Zealand?

Nominally 230 volts single phase and 400 volts three phase at the point of supply. Distribution upstream of that runs at 11 kV and higher. Only a registered electrician should work on mains wiring.

Can voltage be negative?

Yes. Voltage is a potential difference between two points, so the sign depends on which point you treat as the reference. A reading of minus 2.5 V simply means the polarity is the other way round from your reference.