Watts to Milliwatts (W to mW)

1 watt equals 1,000 milliwatts exactly.

1 watt = 1,000 milliwatts

How to convert watts to milliwatts

To convert watts to milliwatts, multiply the number of watts by 1,000. This factor is exact. To go the other way, multiply milliwatts by 0.001.

milliwatts = watts × 1,000

Example: 10 watts = 10,000 milliwatts.

Several different horsepower units exist. This site lists mechanical (745.7 W), metric (735.5 W) and electrical (746 W) horsepower separately.

About these units

Watt (W)

Metric (SI)Current unit

The SI unit of power: one joule per second. A typical LED bulb uses 5–10 W and a laptop 30–60 W.

Credit for the name goes to C. William Siemens, who proposed it in August 1882 in his presidential address to the British Association for the Advancement of Science. He chose it to honor James Watt, the Scottish inventor who in 1776 improved the Newcomen steam engine. An International Conference on Electric Units and Standards adopted Siemens' definition in London in October 1908 as the international watt. After the 1948 General Conference on Weights and Measures the unit was redefined in absolute terms, and in 1960 the 11th General Conference adopted it into the SI as the unit of power.

Today one watt is one joule per second, or equivalently one volt times one ampere. Orders-of-magnitude tables put an LED light bulb at about 7 W and an adult's basal metabolic rate at roughly 100 W. A 100 kg person climbing a 3 m ladder in 5 seconds works at about 600 W, while a laborer can sustain around 75 W over an eight-hour day. The watt measures a rate, so it says how fast energy is being used, not how much has been used in total.

The watt is the reference unit for power on this site.

Sources: Wikipedia: Watt; Wikipedia: Orders of magnitude (power)

Milliwatt (mW)

Metric (SI)Current unit

One thousandth of a watt. Used for lasers and small electronics.

A thousandth of a watt sounds negligible, but it is the working scale for a great deal of light and signal technology. A common laser pointer emits about five milliwatts of light, and a hearing aid draws less than one. The watt is named for James Watt, with the name proposed by C. William Siemens in 1882 and the unit placed in the SI by the General Conference on Weights and Measures in 1960, and the milliwatt simply applies the standard milli prefix to it.

Radio and audio engineers use the milliwatt as a zero point. A level in dBm is a power measured in decibels relative to one milliwatt, so 0 dBm is exactly 1 mW and each 10 dB step multiplies or divides the power by ten. One milliwatt is 0.001 watt, 1,000 microwatts, and 10,000 ergs per second in the older CGS system, since one watt equals 10 million ergs per second.

1 milliwatt = 0.001 watts (exactly).

Sources: Wikipedia: Watt

Related conversions

See all power units.