dBm to watts calculator
Convert RF power between dBm, watts, milliwatts and dBW. Enter any one value and the other three update immediately. The static table below covers common levels from −60 dBm to +60 dBm.
Enter any one value
Conversion formulas
P(mW) = 10(dBm / 10)P(W) = P(mW) / 1000dBm = 10 · log10(P(mW))dBW = dBm − 30dBm to watts conversion table
| dBm | W | mW | dBW |
|---|---|---|---|
| −60 | 1×10−9 | 1×10−6 | −90 |
| −50 | 1×10−8 | 1×10−5 | −80 |
| −40 | 1×10−7 | 0.0001 | −70 |
| −30 | 1×10−6 | 0.001 | −60 |
| −20 | 1×10−5 | 0.01 | −50 |
| −10 | 0.0001 | 0.1 | −40 |
| −3 | 0.000501 | 0.501 | −33 |
| 0 | 0.001 | 1 | −30 |
| 3 | 0.001995 | 1.995 | −27 |
| 10 | 0.01 | 10 | −20 |
| 13 | 0.01995 | 19.95 | −17 |
| 20 | 0.1 | 100 | −10 |
| 23 | 0.1995 | 199.5 | −7 |
| 30 | 1 | 1000 | 0 |
| 33 | 1.995 | 1995 | 3 |
| 36 | 3.981 | 3981 | 6 |
| 40 | 10 | 10000 | 10 |
| 43 | 19.95 | 19953 | 13 |
| 46 | 39.81 | 39811 | 16 |
| 50 | 100 | 100000 | 20 |
| 53 | 199.5 | 199526 | 23 |
| 60 | 1000 | 1×106 | 30 |
Using dBm in RF systems
The difference between dBm and dB
dBm is an absolute power level referenced to 1 mW, while dB is a dimensionless ratio between two quantities. An amplifier gain of 20 dB and an output power of 20 dBm are therefore different measurements. The arithmetic follows the units: adding a 20 dB gain to a 0 dBm input gives 20 dBm, but adding two dBm values has no physical meaning. Convert powers to watts before combining independent sources.
Peak power and average power
Peak and average power can differ by tens of decibels in pulsed RF systems. For duty cycle D, P_avg(dBm) = P_peak(dBm) + 10·log10(D). A 1% duty cycle therefore makes average power 20 dB below peak power. This distinction matters when selecting amplifiers, attenuators and antennas: thermal limits usually track average power, while voltage breakdown and field stress may be governed by peak power.
Antenna power handling is not one constant
An antenna power rating changes with frequency, VSWR, altitude and ambient temperature. At high altitude, reduced air density lowers breakdown voltage and requires derating. A degraded VSWR also increases local electric-field maxima because incident and reflected waves combine along the feed structure. Ask whether a stated rating is continuous-wave, average or peak power, and verify the rating across the intended operating band and installation environment.
Common conversion errors
A frequent error is reading +30 dBm as 30 W; it is exactly 1 W. Another is calculating EIRP from transmitter output while ignoring cable and connector loss before the antenna. In logarithmic calculations, keep absolute power and ratios distinct: dBm plus dB produces dBm, but dBm plus dBm is invalid. When adding independent powers, convert each level to watts, sum the linear values, then convert the result back to dBm.
Frequently asked questions
How many watts is 30 dBm?
30 dBm is 1 watt, because 30 dBm equals 1000 milliwatts.
What is the difference between dBm and dBW?
dBm is referenced to 1 milliwatt, while dBW is referenced to 1 watt. The numerical relationship is dBW = dBm – 30.
Can dBm be negative?
Yes. Negative dBm values represent powers below 1 milliwatt. For example, -30 dBm is 1 microwatt.
How do I add dBm and dB?
Add a dB gain or loss directly to a dBm power level. For example, 10 dBm plus 20 dB gain equals 30 dBm.
What is 0 dBm in watts?
0 dBm is 0.001 watt, which is exactly 1 milliwatt.
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