dBm to Watts Converter

Free dBm to watts calculator with two-way conversion between dBm, watts, milliwatts and dBW. Type a value in any box to convert dBm to watts instantly, or browse the dBm to watts table below for common RF power levels.

dBm to Watts Calculator

dBm (decibel-milliwatts)

Watts (W)

Milliwatts (mW)

dBW (decibel-watts)

1 W

30 dBm = 0 dBW = 1000 mW

P(W) = 10^{((dBm - 30) / 10)} | dBm = 10 x log10(P in watts) + 30

dBm to Watts Table

Reference chart for dBm to watts conversion, with milliwatts and dBW in every row. Tap any row to load it into the calculator.

dBm	Watts	Milliwatts	dBW

Typical RF Power Levels

Thermal noise floor: -174 dBm/Hz = 3.9811 x 10^-21 W/Hz
WiFi receiver sensitivity: about -90 dBm = 0.000000000001 W
Bluetooth transmit: 0 to 10 dBm = 0.001 to 0.01 W
WiFi access point: 20 dBm = 0.1 W (100 mW)
Handheld radio: 30 dBm = 1 W
Cellular base station: 43 dBm = 19.9526 W (about 20 W)
Broadcast / radar: 60 dBm = 1000 W (1 kW)

Remember the two mental anchors: every 3 dB doubles the watts (10^(3/10) = 1.995262, roughly 2), and every 10 dB multiplies the watts by exactly 10.

How the Conversion Works

dBm expresses power on a logarithmic scale relative to 1 milliwatt. To convert dBm to watts, subtract the 30 dB offset between 1 milliwatt and 1 watt, divide by 10, and raise 10 to that power. Converting watts to dBm runs the formula backwards: take log10 of the watts, multiply by 10, and add 30. Because the scale is logarithmic, a small dB change means a large watt change at high power: 50 dBm is 100 W while 60 dBm is 1000 W.

Scope boundary

This page converts dBm to watts (and dBW / mW) as a pure power conversion. The companion tool dbm-to-mw (#866, planned) is scoped to milliwatt-centric RF work: mW-first input, dBm to mW tables and low-power receiver math. Use this page when your answer must be in watts; use #866 when your workflow thinks in milliwatts.

dBm to Watts FAQ

What is the formula to convert dBm to watts?

The formula is P(W) = 10^((dBm - 30) / 10). For example, 30 dBm gives 10^((30 - 30) / 10) = 10^0 = 1 W. The minus 30 shifts the reference from 1 milliwatt (dBm) to 1 watt.

How many watts is 30 dBm?

30 dBm equals exactly 1 W. This is the most-used anchor in RF work: every 10 dB above 30 dBm multiplies the watts by 10, so 40 dBm = 10 W and 50 dBm = 100 W.

How many watts is 0 dBm?

0 dBm equals 0.001 W, which is 1 mW. By definition, 0 dBm is the reference point: 1 milliwatt.

How many watts are 40 dBm and 50 dBm?

40 dBm equals 10 W and 50 dBm equals 100 W. Each 10 dB step multiplies power by 10: 30 dBm = 1 W, 40 dBm = 10 W, 50 dBm = 100 W, 60 dBm = 1000 W.

How do I convert watts to dBm?

Use the inverse formula dBm = 10 x log10(P in watts) + 30. For example, 1 W gives 30 dBm, 2 W gives 33.0103 dBm, and 0.5 W gives 26.9897 dBm.

What is the difference between dBm and dBW?

dBm is referenced to 1 milliwatt, dBW is referenced to 1 watt, so dBW = dBm - 30. For example, 30 dBm = 0 dBW, and 0 dBm = -30 dBW. Both describe the same physical power.

How many watts is 20 dBm?

20 dBm equals 0.1 W, which is 100 mW. This is the typical maximum transmit power of a WiFi access point and many Bluetooth devices.

How many watts is 36 dBm?

36 dBm equals 3.9811 W, commonly rounded to about 4 W. It sits 6 dB above the 30 dBm (1 W) anchor, and 6 dB is a factor of 3.9811.

What is -174 dBm/Hz in watts?

-174 dBm/Hz equals 3.9811 x 10^-21 W/Hz. This is the thermal noise floor at room temperature (290 K), the theoretical minimum noise power per hertz of bandwidth.

Why does adding 3 dB double the watts?

Because 10^(3/10) = 1.995262, which is approximately 2. So 3 dB more means roughly twice the watts, 10 dB more means exactly 10 times the watts, and 20 dB more means 100 times.

What does a negative dBm value mean?

Negative dBm means less than 1 mW. For example, -30 dBm = 0.000001 W (1 microwatt), -60 dBm = 0.000000001 W (1 nanowatt), and -120 dBm = 0.000000000000001 W.

How many dBm is 1 watt?

1 W equals 30 dBm. From the formula: dBm = 10 x log10(1) + 30 = 30 dBm.

Is 0 dBW the same as 0 dBm?

No. 0 dBW equals 30 dBm, which is 1 W. 0 dBm equals -30 dBW, which is 0.001 W (1 mW). The 30 dB offset comes from the 1000x ratio between 1 watt and 1 milliwatt.

How many watts is 43 dBm?

43 dBm equals 19.9526 W, commonly rounded to about 20 W. This is a typical transmit power level for cellular base station radios.

Free tool by NRTechStudio

dBm to Watts Converter

dBm to Watts Calculator

dBm to Watts Table

Typical RF Power Levels

How the Conversion Works

Scope boundary

dBm to Watts FAQ

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