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AESTECHNO
dB

Decibel converter: dBm, mW, W, dBW and dB ratios

Our decibel converter links absolute power (dBm, dBW, W, mW, uW) and dB ratios on one surface. Power uses 10 log10, voltage uses 20 log10 (because P is proportional to V squared). Landmarks: 0 dBm = 1 mW, +30 dBm = 1 W, +3 dB doubles power.

Inputs
Conversion type
Starting value

Used to compute dBµV and the RMS voltage from the absolute power.

Compares the entered power against the standard's limit. Indicative: real conformity also depends on antenna gain, duty cycle and the channel plan.

FCC 15.247: the entered power is conducted power. Above 6 dBi the conducted limit drops 1 dB per dB (47 CFR 15.247(b)(4)).

P 10log 0 x1 3 x2 10 x10 20 x100 V 20log 0 x1 6 x2 20 x10 40 x100 dB (top) -> ratio (bottom)

dB to ratio: power 10 log, voltage 20 log

Result

0 dBm

Breakdown

dBW -30 dBW
Power 1 mW (1 mW)
dBµV @50Ω 107 dBµV
V RMS @50Ω 223.6 mV

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You receive the result with its direct link. Our design house gets a copy and can react to it, simply reply if you want an engineer's eye on it.

Base-10 decibels. 0 dBm = 1 mW. Power ratios use 10 log, voltage ratios 20 log; a voltage-to-power crossing needs the reference impedance.

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Frequently asked questions

FAQ

What is the maximum RED power at 2.4 GHz?
EN 300 328 V2.2.2 caps mean power at 20 dBm e.i.r.p. (100 mW) for all wideband equipment, FHSS, DSSS or OFDM. Non-FHSS equipment also has a 10 dBm/MHz e.i.r.p. spectral density limit: that is what constrains a narrow signal, or the peak of a DSSS spectrum, before 20 dBm. The verdict compares the entered total power against those ceilings, and against EN 300 220 (868 and 869.4 MHz, as e.r.p.), EN 301 893 (5 GHz, with or without TPC) and FCC 15.247 (conducted power plus antenna gain). It is indicative: spectral density, duty cycle and the channel plan are not checked.
Why does power use 10 log and voltage use 20 log?
Because power is proportional to voltage squared at equal impedance (P = V squared / Z). A voltage ratio r therefore gives a power ratio r squared, and 10 log10(r squared) = 20 log10(r). The factor 20 is not a separate rule, it is the factor 10 applied to a quadratic quantity. Reference: IEC 60027-3.
What is the difference between dBm and dBW?
dBm references 1 milliwatt, dBW references 1 watt. Since 1 W = 1000 mW and 10 log10(1000) = 30, you always have dBm = dBW + 30. So 0 dBm = -30 dBW = 1 mW, and +30 dBm = 0 dBW = 1 W. Our tool shows both references plus the linear values (W, mW, uW) side by side.
What do the +3 dB, +6 dB and -3 dB landmarks mean?
+3 dB is a doubling of power (exactly +3.01 dB for x2). +6 dB is a doubling of voltage (exactly +6.02 dB), which is also x4 in power. -3 dB is half power, the -3 dB point that defines a filter bandwidth. These landmarks let you sanity-check a calculation in your head before trusting the tool.
Why is a reference impedance needed to go from voltage to power?
A voltage alone does not define a power: you need P = V squared / Z. Without an impedance, the voltage to absolute power crossing is undefined. We offer 50 ohm (RF, default), 75 ohm (video, antenna) and 600 ohm (audio). For a pure ratio at one constant impedance, Z cancels out and is not required.
Why is a ratio of 0 or negative rejected?
The base-10 logarithm is only defined for strictly positive values. A ratio of 0 would return minus infinity, and a negative ratio has no physical meaning for a power or an amplitude. The tool therefore requires a ratio greater than zero and returns a message rather than a NaN or infinite result, keeping every conversion usable.
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AESTECHNO is an electronics design office near Montpellier, France, with 10+ years of experience in RF, IoT and embedded design, and a 100% success rate on CE/FCC certifications, across dozens of campaigns run over more than 10 years of practice.