This tool converts voltage units, not mains supplies. One kilovolt is 1,000 V, one millivolt is 0.001 V and one microvolt is 0.000001 V. Sensor outputs and biosignals such as ECG are measured in millivolts or microvolts, household mains is 230 V in India and Europe or 120 V in North America, and transmission lines run at hundreds of kilovolts. Use it to read datasheets and meter readings correctly. If you need to plug a 120 V appliance into a 230 V socket, that requires a physical step-down transformer, which this calculator cannot replace.
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