Milliwatts

Milliwatt (symbol mW) is a unit of power in the International System of Units (SI). It represents one thousandth of a watt. The prefix milli- denotes 10^-3, so 1 mW = 0.001 W and 1 W = 1000 mW. The milliwatt is commonly used to express small power levels in electronics and communication systems.

In electronic circuits, milliwatts describe consumer device power consumption and signal power levels, such as LED output, sensor bias, and radio frequency (RF) transmitter power. In wireless communications, transmit power is often specified in dBm, where 0 dBm equals 1 mW, and higher values indicate stronger signals. Common examples: Wi-Fi or Bluetooth transmitters may operate from a few milliwatts up to tens or hundreds of milliwatts depending on regulatory limits and design. Laser diodes, photodetectors, and infrared emitters are also rated in milliwatts for optical power output or received optical power.

To relate energy to time, milliwatts paired with time yield millijoules or milliwatt-hours: energy = power × time. Care is needed when comparing devices with different duty cycles. The milliwatt is a practical unit for small-scale power measurements, whereas watts cover most household and industrial devices and microwatts or nanowatts are used for extremely low-power systems, such as biosensors or energy harvesting circuits.

See also: Watt, dBm, microwatt.