Voltage Conversion Calculator: Volts, Millivolts and More

A voltage conversion calculator changes a voltage value from one unit to another, such as volts to millivolts or kilovolts. Enter the voltage and choose its starting and target units to get the equivalent value; this calculator handles unit conversion, not conversion between AC and DC or between different electrical circuits.

Formula

The conversion is a ratio of unit factors:

Converted voltage = input voltage × source-unit factor ÷ target-unit factor

• Input voltage is the number entered, in the unit selected as the source.
• Source-unit factor is the number of volts in one source unit.
• Target-unit factor is the number of volts in one target unit.
• Converted voltage is the result in the selected target unit.

For example, the factor for millivolts is 0.001 because 1 mV equals 0.001 V. The factor for kilovolts is 1,000 because 1 kV equals 1,000 V. The calculator’s second output expresses the same input as volts, which can help check a conversion.

Worked Example

Using the defaults, convert 12 V to millivolts. The factor for volts is 1, and the factor for millivolts is 0.001.

1. Converted voltage = 12 × 1 ÷ 0.001.
2. Converted voltage = 12,000 mV.
3. Equivalent voltage = 12 × 1 = 12 V.

The calculator displays 12,000 mV and 12 V. These are the same voltage stated in different units.

Voltage Units and Their Scale

The volt (V) is the SI unit for electric potential difference. Common submultiples and multiples use metric prefixes: a millivolt (mV) is one-thousandth of a volt, and a microvolt (µV) is one-millionth of a volt. A kilovolt (kV) is 1,000 volts, while a megavolt (MV) is 1,000,000 volts.

In symbols, the relationships are:

• 1 V = 1,000 mV = 1,000,000 µV.
• 1 kV = 1,000 V.
• 1 MV = 1,000 kV = 1,000,000 V.

The capitalization matters: mV means millivolts, while MV means megavolts. Confusing the two changes the scale by a factor of one billion. The calculator treats the listed unit symbols according to these standard metric prefixes.

When to Use a Voltage Converter

A unit converter is useful when a label, specification, diagram, or measurement uses a different voltage unit from the one you need. It can also help check arithmetic in a report or make small sensor readings easier to interpret. For example, 0.025 V is 25 mV, and 3.3 kV is 3,300 V.

To use the calculator:

1. Enter the numerical voltage. The default is 12 V.
2. Choose the unit that describes the number you entered.
3. Choose the unit in which you want the answer.
4. Read the converted voltage and, if useful, its equivalent in volts.

Changing only the selected units does not change the underlying voltage. It changes the way that value is written. If the source and target units are the same, the numerical result remains unchanged.

What Unit Conversion Does—and Does Not—Mean

Voltage conversion here is a mathematical change of units. It does not transform a power supply’s output, alter a circuit, or make a device compatible with a different supply. A result of 12 V is not interchangeable with a 12 A current rating, and voltage alone does not specify how much current a source can provide.

It is also distinct from a voltage converter or transformer as a physical device. A circuit can raise or lower voltage, but its input and output may differ in current, power, waveform, and other characteristics. This calculator does not predict those properties or account for losses.

AC and DC are another separate issue. A voltage value may describe direct current or alternating current; converting its unit does not change the waveform. AC readings may be specified as RMS, peak, or peak-to-peak, which are different ways to describe a varying signal. Do not treat those values as equivalent merely because they are all expressed in volts.

Accuracy, Rounding, and Common Mistakes

The conversion factors are exact for the metric prefixes used here, but displayed results are rounded to six decimal places. A very small value may therefore appear as zero at the chosen precision, or a long decimal may be shortened. Keep more digits in intermediate calculations when precision matters, and match the reported precision to the source measurement rather than assuming the calculator creates extra measurement accuracy.

• Check the starting unit: selecting mV for a value given in V makes the answer 1,000 times too small or large.
• Distinguish mV from MV: lowercase m is milli; uppercase M is mega.
• Keep the quantity consistent: this tool converts voltage units, not watts, amps, resistance, or energy.
• Check the measurement convention: for AC, determine whether a specification is RMS, peak, or another stated measure before comparing readings.

The calculator accepts nonnegative voltage values. If a technical convention or analysis uses a signed voltage, such as a signal measured relative to a reference point, retain the sign separately; this simple converter is designed for ordinary nonnegative magnitude conversions.

Frequently Asked Questions

How many millivolts are in one volt?
There are 1,000 millivolts in one volt. Multiply volts by 1,000 to convert to millivolts.

How many volts are in one kilovolt?
One kilovolt equals 1,000 volts. Multiply the kilovolt value by 1,000.

How do I convert millivolts to volts?
Divide millivolts by 1,000. For example, 250 mV ÷ 1,000 = 0.25 V.

Are 12 V and 12,000 mV the same?
Yes. Since 1 V equals 1,000 mV, 12 V equals 12,000 mV.

Does converting volts change AC into DC?
No. Unit conversion only changes the numerical expression and unit. It does not change an electrical signal’s AC or DC nature, waveform, or source.

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in v | Voltage | V | 12 | 0
sel from | Convert from | V=1, mV=0.001, µV=0.000001, kV=1000, MV=1000000
sel to | Convert to | V=1, mV=0.001, µV=0.000001, kV=1000, MV=1000000
out result | Converted voltage | selected unit | v * from / to | 6
out volts | Equivalent voltage | V | v * from | 6