Voltage Unit Converter

How to use this calculator

Voltage value field — Type the number you want to convert. Decimals are fine. So are large numbers: 120,000 µV is a valid input and the converter won’t complain.

From unit — The unit your value is currently in. Pick from the dropdown: Volt, Millivolt, Microvolt, Kilovolt.

To unit — The unit you want to convert into. The converted result shows large in the output panel.

The result panel shows all 4 units simultaneously, not just the pair you selected. So if you convert 5V to mV, you also see the microvolt and kilovolt values without running the tool again.

The conversion formula

Every voltage conversion is multiplication or division by a power of 10. That’s it. There’s no weird ratio like 3.78541 liters per US gallon. Voltage units are all metric, so they scale cleanly.

The volt is the base unit. Everything else is just the volt multiplied or divided by 1,000.

1 kilovolt = 1,000 volts 1 volt = 1,000 millivolts 1 millivolt = 1,000 microvolts

So going from kilovolts all the way down to microvolts: multiply by 1,000,000,000 (10⁹). Going the other direction: divide by the same.

Because all voltage units are powers of 10 apart, you can verify any result mentally. 5 kV to mV? That’s 5 × 1,000 × 1,000 = 5,000,000 mV. If your result has too many or too few zeros, you’ve multiplied in the wrong direction.

Full unit reference table

The microvolt lives in a world you can’t feel. A typical ECG signal (your heart, electrically) runs between 0.5 and 4 mV at the skin surface, which is 500 to 4,000 µV. Noise from the room’s electrical wiring can swamp that. This is why ECG machines have such aggressive shielding and filtering.

The kilovolt lives in a world that can kill you. A standard overhead power distribution line in the US runs at 4 kV to 35 kV. Transmission lines (the big ones strung between tall towers across open land) run at 115 kV to 765 kV. A 500 kV line is 500,000 volts. You don’t need a converter for that; you need to stay well clear of it.

Common conversions at a glance

The factors you’ll use 90% of the time: volts to millivolts (×1,000) and millivolts to volts (÷1,000). Everything else is just chaining those together.

Real-world examples

Reading a battery datasheet

You’ve got a lithium coin cell. The datasheet says nominal voltage is 3.0V, and the cutoff voltage (the point where the battery’s considered dead) is 2.0V. Your circuit’s ADC (analog-to-digital converter) reports measurements in millivolts.

Thermocouple output

Type K thermocouples (the ones used in ovens, kilns, and industrial furnaces) output roughly 41 µV per degree Celsius. At 500°C, the output is about 20.64 mV. A lot of thermocouple amplifier ICs report their output in millivolts and your target temperature is in degrees, so the conversion chain goes: millivolts → microvolts → temperature.

Power line voltage for an engineer

An electrical engineer is specifying insulation for a 345 kV transmission line and needs the value in volts for a component spec sheet that lists voltage ratings in plain volts.

Audio equipment: input sensitivity

A microphone preamplifier has an input sensitivity of 1.5 mV (the signal level that produces a standard output). A condenser microphone puts out about 10 mV at close range. You want to know if the signal is above or below the preamp’s sensitivity threshold, with both numbers in the same unit.

But if the mic spec gives output in µV (some do), the comparison gets awkward fast.

Radio signal strength

A radio receiver is picking up a signal at 50 µV. The receiver’s spec sheet rates minimum sensitivity at 0.1 mV. Is the signal strong enough?

Where voltage unit confusion actually causes problems

The stakes are low in most contexts. You use mV when you mean V, your code produces a reading 1,000 times too large, you notice immediately, and you fix it.

But a few areas are worth watching.

Medical devices. ECG and EEG signals are in the µV-to-mV range. A 1 mV calibration signal is a standard in ECG machines (there’s a 1 mV “calibration pulse” at the start of most ECG printouts). If software misinterprets this as 1V, the amplitude scaling on every waveform is wrong, and so is every measurement derived from it. In clinical settings, a misread amplitude isn’t just an inconvenience.

Sensor calibration. Pressure sensors, load cells, and strain gauges output millivolt-level signals, typically expressed as mV per volt of excitation (e.g., 2 mV/V). If you feed the sensor 5V of excitation and expect a full-scale output, that’s 10 mV at full scale, not 10V. Getting this wrong during calibration means every measurement downstream is off by a factor of 1,000.

High-voltage safety. This is less about unit confusion and more about unit awareness. 4 kV sounds smaller than 4,000 V, even though they’re identical. Anyone working near electrical infrastructure should do the mental conversion automatically: treat kilovolts as thousands of volts, because the hazard scales linearly with voltage, and 12 kV is as lethal as 12,000 V (which is to say: extremely).

AC vs DC: a separate thing the converter doesn’t handle

Voltage has units (volts, millivolts, etc.) and it also has a type: AC (alternating current) or DC (direct current).

The converter converts units. It doesn’t convert between AC and DC, because that’s a different kind of conversion entirely, one that requires knowing frequency, waveform shape, and what measurement method you’re using (peak, RMS, peak-to-peak).

Here’s where people get tripped up.

When you plug something into a US wall outlet, the supply is 120V AC. That 120V is an RMS (root mean square) value. The actual peak voltage on that line is about 169.7V. The peak-to-peak (positive peak to negative peak) is about 339.4V.

Three different numbers, same outlet, all technically correct depending on what you’re measuring.

A DC battery rated at 12V is 12V in every sense: peak, RMS, peak-to-peak all equal 12V because DC doesn’t oscillate.

The converter’s voltage values assume you know which type of voltage you’re dealing with. If you’re converting 120V to mV, you get 120,000 mV. Whether that’s AC RMS, AC peak, or DC is your problem to track, not the converter’s.

The scale problem: why voltage spans 15 orders of magnitude

Voltage in electronics covers an absurd range. A single-cell lithium battery is 3.7V. A thunderstorm lightning bolt is roughly 300 million volts (300 MV, or 300,000 kV). That’s 11 orders of magnitude.

Within everyday electrical work, the useful range is roughly:

• Biosignals: 1 µV to 100 mV (ECG, EEG, EMG)
• Low-power electronics: 1 mV to 5V (sensors, microcontrollers, audio)
• Standard electronics: 3V to 48V (USB, batteries, industrial DC)
• Mains power: 100V to 240V AC
• Industrial: 480V to 690V AC (three-phase systems)
• High voltage: 1 kV to 35 kV (distribution lines, X-ray, industrial equipment)
• Transmission: 115 kV to 765 kV (long-distance power grids)

The converter covers the first 4 tiers comfortably. For transmission-level voltages in kV, the converter still works: 345 kV to volts is 345,000 V, and the math is correct. Whether you should be near a 345 kV line without proper training and PPE is a different question with an obvious answer.

Common mistakes

Millivolts vs volts in microcontroller code. An Arduino ADC reading is typically 0 to 1023 for a 0-to-5V range. Each step is about 4.88 mV. Some code examples express the reference as 5000 (in mV) to avoid floating point; others use 5.0 (in V). Mixing the two without converting gives you readings that are 1,000 times off. The symptom is a temperature sensor reading 25,000°C instead of 25°C. You’ve seen this bug. Maybe you’ve written this bug.

Confusing voltage with power. Volts measure electrical potential, not power. Power is watts (voltage × current). A 9V battery and a 9V power supply are both 9V, but a 9V/1A supply can deliver 9W and a 9V/0.1A supply can only deliver 0.9W. Converting volts to millivolts doesn’t tell you anything about power. That requires knowing current too.

Treating AC voltage as DC in calculations. If you’re using 120V AC to calculate the power dissipated in a resistor (P = V²/R), make sure your 120V is the RMS value before plugging it in. The formula works correctly with RMS volts. Using peak voltage (169.7V) instead of RMS gives you a power result that’s twice the actual average power delivered.

The bottom line

Voltage unit conversions are all powers of 10. Millivolts to volts: divide by 1,000. Volts to kilovolts: divide by 1,000 again. Microvolts to millivolts: divide by 1,000. Every step in the chain is the same operation.

The converter does this instantly and shows all 4 units at once, so you’re not running it 3 times for the same value.

The two places to pay attention: medical/sensor applications where millivolt-level signals matter, and any work near high-voltage equipment where kilovolts need to be mentally translated into thousands of volts before you get anywhere near the hardware.