Watts to dBm Online Calculator

This online calculator converts power values from watts (W) to dBm (decibel-milliwatts). Watt is the SI unit of power. dBm is a logarithmic unit used in telecommunications, RF systems, and audio engineering.

Watts (W) to dBm Converter

Enter a value in watts and press the button

Watts (W)

Result in dBm

Swap

Calculation process will appear here.

Decimal Places

How to Use

Enter a power value in watts (must be greater than 0).
Select the number of decimal places to round the result (default is 6).
Click “Convert” to calculate the corresponding value in dBm.
The result will appear below the input field.
Click “Copy Result” to copy the output to clipboard.
Click “Clear All” to reset all fields.
Use the “Swap” button to switch to the dBm to Watts version of this tool.

Unit Definitions

Watt (W)

The watt is the SI unit of power, symbol W. It represents the rate of energy transfer and is defined as 1 joule per second. Widely used across electrical and mechanical systems, it quantifies how much power a device consumes or delivers. System: SI. 1 W = 1000 milliwatts (mW). In this calculator, it’s the input value used to compute dBm.

Decibel-milliwatts (dBm)

dBm is a logarithmic unit that expresses absolute power relative to 1 milliwatt. It is commonly used in RF engineering, audio levels, and telecom equipment to express signal strength. System: logarithmic (non-SI). Abbreviation: dBm. 0 dBm = 1 mW, and 1 W = 30 dBm. The conversion formula is: dBm = 10 × log₁₀(Watts) + 30.

Conversion Table

Watts (W)	dBm
0.001	0.00E+00
0.00126	1.00E+00
0.00158	2.00E+00
0.001995	3
0.00316	5
0.01	10
0.01585	12
0.01995	13
0.02512	14
0.03162	15
0.03981	16
0.05012	17
0.0631	18
0.07943	19
0.1	20
0.12589	21
0.15849	22
0.19953	23
0.25119	24
0.31623	25
0.39811	26
0.50119	27
0.63095	28
0.79433	29
1	30
1.2589	31
1.5849	32
1.9953	33
2.5119	34
3.1623	35
3.9811	36
5.0119	37
6.3096	38
7.9433	39
10	40
19.95	43
25.12	44
31.62	45
39.81	46
50.12	47
63.1	48
79.43	49
100	50
1000	60