Enter value in W:
Formula: MW = W × 1e-06
Converting between watts (W) and milliwatts (mW) is a fundamental task in electronics, instrumentation, and scientific measurement. Watts quantify power at the base SI scale, while milliwatts—one-thousandth of a watt—provide a convenient unit for low-power devices such as sensors, RF modules, and microcontrollers. Mastering this conversion ensures precise component selection, accurate data logging, and clear reporting.
The watt is defined as one joule of energy transferred or converted per second:
1 W = 1 J/s
This universal definition underpins electrical, mechanical, and thermal power measurements across laboratories, industry, and research.
A milliwatt represents one-thousandth of a watt:
1 mW = 0.001 W = 1 × 10−3 W
Using milliwatts simplifies representation of small power levels—common in wireless transmitters, low-power LEDs, and battery-powered sensors.
Since 1 mW = 0.001 W, converting watts to milliwatts involves multiplication by 1,000:
mW = W × 1,000
Conversely, to convert milliwatts to watts, divide by 1,000:
W = mW ÷ 1,000
| Watts (W) | Mill watts (mW) | Operation |
|---|---|---|
| 1 W | 1,000 mW | × 1,000 |
| 0.5 W | 500 mW | 0.5 × 1,000 |
| 0.002 W | 2 mW | 0.002 × 1,000 |
| 250 mW | 0.25 W | ÷ 1,000 |
Convert 0.037 W to mW:
0.037 W × 1,000 = 37 mW
Milliwatts provide readability and resolution for low-power applications:
Transmitter power is quoted in mW before converting to decibels:
dBm = 10 × log₁₀(Power (mW))
For a 50 mW transmitter, dBm = 10 × log₁₀(50) ≈ 17 dBm.
Designers calculate total draw in mW to estimate battery runtime:
Runtime (h) = Battery Capacity (mAh) × Battery Voltage (V) ÷ Load Power (mW)
If cell A2 contains watts:
=A2 * 1000 // W to mW
=A2 / 1000 // mW to W
Identical formulas apply; use named ranges for clarity (e.g., =watts * 1000).
function wToMw(watts) {
return watts * 1000;
}
function mwToW(milliwatts) {
return milliwatts / 1000;
}
// Usage
console.log(wToMw(0.12)); // 120 mW
console.log(mwToW(250)); // 0.25 W
def w_to_mw(w):
return w * 1000
def mw_to_w(mw):
return mw / 1000
print(w_to_mw(0.005)) # 5.0
In high-precision contexts:
Label units explicitly (e.g., “Power: 37.00 mW”) and note the conversion factor in footnotes.
Avoid these mistakes:
Oscilloscopes measure instantaneous power in watts; converting to mW on capture enables fine-grained analysis of microsecond-scale events.
In link-budget calculations, both transmit and receive powers use mW for linear arithmetic before converting to decibels.
Plot time-series of mW consumption for IoT devices to identify duty-cycle patterns and optimize sleep intervals.
A wireless temperature sensor draws 15 mW while transmitting and 2 mW in sleep mode. Average draw:
Converting to watts: 2.0217 mW ÷ 1,000 ≈ 0.00202 W informs power-budget calculations.
In lab courses, students convert LED forward power (e.g., 20 mW) into watts and calculate resistor values for series current limiting.
Given a 5 V supply and 20 mW LED forward power with 2 V drop:
Emerging ultra-low-power electronics operate in microwatts (µW) and nanowatts (nW). Converting consistently across W, mW, and beyond is critical for energy-harvesting devices and implantable sensors.
Although the arithmetic of watts to milliwatts is straightforward, embedding accurate conversion practices throughout design, measurement, and reporting workflows ensures clarity, precision, and interoperability in today’s low-power electronic systems.
In high-precision contexts:
Label units explicitly (e.g., “Power: 37.00 mW”) and note the conversion factor in footnotes.
Avoid these mistakes:
Oscilloscopes measure instantaneous power in watts; converting to mW on capture enables fine-grained analysis of microsecond-scale events.
In link-budget calculations, both transmit and receive powers use mW for linear arithmetic before converting to decibels.
Plot time-series of mW consumption for IoT devices to identify duty-cycle patterns and optimize sleep intervals.
Although the arithmetic of watts to milliwatts is straightforward, embedding accurate conversion practices throughout design, measurement, and reporting workflows ensures clarity, precision, and interoperability in today’s low-power electronic systems.