What is watt?
The watt is the SI base unit of power. It is universally used to measure the rate of energy consumption or production in electrical appliances, engines, lighting, and virtually all power-related specifications.
Real-world uses
The watt is the SI unit of power, used to rate electrical appliances (a kettle is about 2,000 W, an LED bulb 8–12 W), solar panels, audio amplifiers, and motors. Electricity generation at power stations and renewable installations is measured in watts and its multiples.
History
Named after Scottish engineer James Watt (1736–1819), the unit was adopted by the Second Congress of the British Association for the Advancement of Science in 1882. Watt's improvements to the steam engine were foundational to the Industrial Revolution.
Common mistakes
Confusing watts (power) with watt-hours (energy). A 100 W light bulb uses 100 watt-hours of energy per hour. Also, equating wattage with brightness for LED bulbs—lumens measure brightness, watts measure power consumption.
What is milliwatt?
A milliwatt is a unit of power equal to one thousandth of a watt. It is used in low-power electronics, wireless communication systems, laser specifications, and medical device power ratings.
Real-world uses
Milliwatts measure the power of laser pointers (Class 1: <1 mW; Class 3B: up to 500 mW), Bluetooth radios (typically 1–100 mW), Wi-Fi transmitters, and fibre optic signals. They are used in optical communications, consumer electronics, and medical laser specifications.
History
Milliwatts became relevant as the miniaturisation era brought small electrical and optical devices into widespread use from the mid-20th century. Consumer electronics, telecommunications, and biomedical equipment all required power specifications at this sub-watt scale.
Common mistakes
Confusing milliwatts (mW) with microwatts (µW)—1 mW = 1,000 µW. Also, assuming all laser pointers operate at the same power level; safety regulations classify lasers by output power in mW, and even small increases can be hazardous to the eyes.
When is this conversion used?
Converting watt to milliwatt is useful in the power domain when comparing values across different measurement standards or applying formulas that require a specific unit.
Worked examples
1 watt = 1,000 milliwatt
1 milliwatt = 0.001 watt
How to convert watt to milliwatt
To convert watt to milliwatt, multiply the value by 1,000.
To convert milliwatt back to watt, multiply by 0.001.
Measurement standards
The watt is the SI derived unit of power, defined as one joule per second (kg·m²/s³). Horsepower remains in widespread informal use, particularly in the automotive industry, but has no single universal definition across regions.
Did you know?
The human body at rest produces about 80 watts of power — roughly enough to keep an incandescent light bulb glowing. During intense exercise, a trained cyclist can sustain over 400 watts, and elite sprinters briefly exceed 2,000 watts.
Quick reference: watt to milliwatt
| watt | milliwatt |
|---|---|
| 0.1 | 100 |
| 0.5 | 500 |
| 1 | 1,000 |
| 2 | 2,000 |
| 5 | 5,000 |
| 10 | 10,000 |
| 25 | 25,000 |
| 50 | 50,000 |
| 100 | 100,000 |
| 250 | 250,000 |
| 500 | 500,000 |
| 1,000 | 1,000,000 |
Common values
| watt | milliwatt | |
|---|---|---|
| LED light bulb | 10 watt | 10,000 milliwatt |
| Desktop computer | 300 watt | 300,000 milliwatt |
| Microwave oven | 1,000 watt | 1,000,000 milliwatt |
| Small car engine | 75,000 watt | 75,000,000 milliwatt |
| Wind turbine (large) | 3,000,000 watt | 3.000000e+09 milliwatt |
Available Power units
More watt conversions
- Convert watt to kilowatt
- Convert watt to horsepower (mechanical)
- Convert watt to megawatt
- Convert watt to gigawatt
- Convert watt to milliwatt
- Convert watt to microwatt
- Convert watt to BTU per hour
- Convert watt to kilocalorie per hour
- Convert watt to ton of refrigeration
Assumption: horsepower values use mechanical horsepower.