Watts to Milliwatts Converter
Enter the power in watts below to convert it to milliwatts.
Convert Watts to Milliwatts
Enter a value in watts (W) to convert to milliwatts (mW).
Watt to Milliwatt Conversion Table
Table showing various watt measurements converted to milliwatts. Click any preset value or arrow to load it into the converter.
How to Convert Watts to Milliwatts
To convert watts to milliwatts, multiply the power by the following conversion ratio: 1,000 milliwatts/watt.
Since one watt is equal to 1,000 milliwatts, you can use this simple formula to convert:
The power in milliwatts is equal to the power in watts multiplied by 1,000.
For example, here's how to convert 5 watts to milliwatts using the formula above.
How Many Milliwatts Are in a Watt?
There are 1,000 milliwatts in a watt, which is why we use this value in the formula above.
Our watt to milliwatt calculator automatically converts your power measurements with full decimal and scientific precision across US customary, imperial, and SI metric standards.
Watts and milliwatts are both units used to measure power. Keep reading to learn more about each unit.
What Is a Watt?
Coherent SI unit of power equal to 1 Joule per second (1 J/s). It serves as a primary reference unit for measuring power across scientific and practical applications. [1]
The watt is classified as an International System of Units (SI) unit of power. Watts can be abbreviated as W; for example, 1 watt can be written as 1 W.
As the primary coherent reference unit for power in this category, all other power units are mathematically anchored to the watt (W).
In practice, watts (W) are widely used across standard power applications within International System of Units (SI) workflows, engineering documentation, and technical data sheets.
What Is a Milliwatt?
A milliwatt is a unit of power equal to 1/1,000 of a watt (0.001 W). One-thousandth of a Watt. [2]
The milliwatt is classified as a metric and SI-compatible unit of power. Milliwatts can be abbreviated as mW; for example, 1 milliwatt can be written as 1 mW.
In the metric system, "milli" is the standard SI prefix for thousandths, or 10⁻³. This makes the milliwatt (mW) a convenient decimal multiple of the watt (W).
In practice, milliwatts (mW) are widely used across fine-tolerance laboratory, analytical, and micro-scale power measurements within SI metric workflows, engineering documentation, and technical data sheets.
When converting power between watts (W) and milliwatts (mW), keep full floating-point precision (1 W = 1,000 mW; 1 mW = 0.001 W) during intermediate calculations and round only the final milliwatt figure to match your instrument tolerance.
More Watt & Milliwatt Conversions
Need to calculate in the opposite direction? Use our milliwatts to watts calculator to switch your starting unit immediately. You can also explore related tools such as converting milliwatts to watts, converting watts to horsepower (hp), or converting watts to kilowatts.
Frequently Asked Questions
References
- [1]NIST SP 811 StandardNIST SP 811 (NIST SP 811 App. B.9 (Power & Radiant Flux))·Power Metrology Standard — Watts (W) to Milliwatts (mW)
- [2]NIST CUU SpecificationNIST CUU (Derived SI Unit: Watt (W))·Unit Specifications: Watt (W) & Milliwatt (mW)
- [3]BIPM ReferenceBIPM (SI Brochure (9th Ed.) — Power)·Conversion Factors & Mathematical Basis (W to mW)