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Electrical Units Converter – Volts, Amps, Ohms and Watts

Convert voltage, current, resistance and power prefixes with this electrical units converter, from millivolts to kilowatts.

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Runs in your browser – your data never leaves your device Also available via our free API

Common conversions

From unit Value To unit Result
Kilovolts (kV) 1 Volts (V) 1,000
Volts (V) 1 Millivolts (mV) 1,000
Amperes (A) 1 Milliamperes (mA) 1,000
Kiloamperes (kA) 1 Amperes (A) 1,000
Kiloohms (kΩ) 1 Ohms (Ω) 1,000
Megaohms (MΩ) 1 Kiloohms (kΩ) 1,000
Ohms (Ω) 1 Milliohms (mΩ) 1,000
Horsepower (hp) 1 Kilowatts (kW) 0.7457
Metric horsepower (PS) 1 Kilowatts (kW) 0.7355
Kilowatts (kW) 1 Horsepower (hp) 1.341
BTU per hour 1,000 Watts (W) 293.0711

How to use the Electrical Units Converter

  1. 1 Choose the quantity: voltage, current, resistance or power.
  2. 2 Enter the value and choose its unit, for example milliamps.
  3. 3 Choose the target unit, for example amps, and read the result.

Four electrical quantities

  • Voltage (volt, V) – the electrical “pressure” that pushes current through a circuit. Also millivolts (mV) and kilovolts (kV).
  • Current (ampere, A) – the flow of electric charge. Also milliamps (mA) and kiloamps (kA).
  • Resistance (ohm, Ω) – how strongly a component opposes current. Also milliohms (mΩ), kilohms (kΩ) and megohms (MΩ).
  • Power (watt, W) – the rate at which electrical energy is used. Also kilowatts (kW), megawatts (MW) and horsepower.

Each quantity uses the same metric prefixes: milli = 1/1,000, kilo = 1,000 and mega = 1,000,000. So 4.7 kΩ is 4,700 Ω, 500 mA is 0.5 A and 2.5 kW is 2,500 W.

You cannot convert volts into amps directly

Volts, amps, ohms and watts measure different things, so a converter can only change the prefix within one quantity. To get from one quantity to another you need a second value and the relationships between them:

  • Ohm’s law: V = I × R, so I = V ÷ R and R = V ÷ I
  • Power: P = V × I, P = I² × R and P = V² ÷ R

For example, a 2,300 W kettle on a 230 V supply draws 2,300 ÷ 230 = 10 A. A 12 V LED strip drawing 1.5 A uses 18 W. A 5 V signal across a 1 kΩ resistor drives 5 mA.

Typical values

  • AA battery: 1.5 V; car battery: 12 V; USB: 5 V (up to 20 V with USB Power Delivery)
  • Mains: 230 V in Europe, 120 V in North America
  • Phone charger: around 1–3 A; household circuit breaker: 16 A in much of Europe
  • Common resistors: from a few ohms to several megohms

Safety

Mains voltage and high currents can be lethal. Use these conversions for planning and learning, and leave work on fixed installations to a qualified electrician.

Sources

Conversion factors follow the SI definitions in the BIPM SI Brochure and the exact factors for US customary and imperial units in NIST Special Publication 811.

Frequently asked questions

How many milliamps are in an amp?

One ampere is 1,000 milliamps (mA).

How many ohms is 1 kΩ?

One kilohm is 1,000 ohms; one megohm is 1,000,000 ohms.

How do I convert watts to amps?

Divide watts by volts: amps = watts ÷ volts. A 1,000 W device on 230 V draws about 4.35 A.

Can I convert volts to watts?

Only if you also know the current or resistance: watts = volts × amps.

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