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dBm to Watts Calculator

Created by Purnima Singh, PhD
Reviewed by Steven Wooding
Last updated: Jan 18, 2024

Omni's dBm to watts calculator allows you to switch between decibels per milliwatt (dBm) and watts (W)/milliwatts (mW).

Continue reading this article to learn:

  • What is dBm?
  • What is the difference between dBm and dB?
  • How to convert from dBm to watts (W) or dBm to mW and vice-versa?

You will also learn how to use the dBm to watts calculator.

If you are interested in converting between other power units, our power converter might be the right tool for you.

What is dBm?

Decibels per milliwatt or dBm is a measure of power level. We often express sound intensity level or the power level of an electrical signal using a relative unit of measurement called the decibel or dB. For example, we can write power level in decibels as the ratio:

 ⁣P (dB)=10 log10(P2P1),\!\small \text{P (dB)} = 10\ \text{log}_{10} \left (\frac{P_2}{P_1} \right),

where P1P_1 and P2P_2 are the power in watts, with P1P_1 usually being the reference power.

When we express power level in decibels (dB) by using P1=1.0 mWP_1 = 1.0\ \text{mW} as a reference, we indicate the power level as dBm.

🙋 The terms decibels (dB) or decibel milliwatts (dBm) do not measure power. Instead, they give a relative comparison (or ratio) between two power values.

Formula for dBm to watts conversion

To convert from dBm to watts, we will use the following formula:

 ⁣P(W)=1W×10P(dBm)101000\!\small P (\text W) = 1 \text W \times \frac{10^ \frac{P(\text{dBm})}{10}}{1000}


  • P(W)P(\text W) – Power in watts (W); and
  • P(dBm)P(\text{dBm}) – Power in decibel-milliwatts (dBm).

Rearranging the above equation, we will get the formula for converting from watts to dBm:

 ⁣P(dBm)=10×log10(1000×P(W)1W)=10×log10(P(W)1W)+30\!\footnotesize \begin{align*} P (\text{dBm}) &= 10 \times \text{log}_{10} \left ( \frac{1000 \times P (\text W)}{ 1 \text W} \right )\\\\ & = 10 \times \text{log}_{10} \left ( \frac{P (\text W)}{ 1 \text W} \right ) + 30 \end{align*}

dBm to watts conversion example

As an example, let us convert 50 dBm to watts. We will use the dBm to watts formula:

P(W)=1 W×10P(dBm)101000=1 W×1050101000=1 W×1051000=100 W\small \begin{align*} P (\text W) &= 1\ \text W \times \frac{10^ \frac{P(\text{dBm})}{10}}{1000}\\\\ &= 1\ \text W \times \frac{10^ \frac{50}{10}}{1000}\\\\ &= 1\ \text W \times \frac{10^5}{1000}\\\\ &= 100\ \text W \end{align*}

Hence, 50 dBm is equivalent to 100 watts. The following dBm to watts conversion table shows a chart that you can use for converting certain specific values.

dBm to watts conversion table.

Power (dBm)

Power (W)

-30 dBm

0.000001 W

-20 dBm

0.00001 W

-10 dBm

0.0001 W

0 dBm

0.001 W

1 dBm

0.0012589 W

2 dBm

0.0015849 W

3 dBm

0.0019953 W

4 dBm

0.0025119 W

5 dBm

0.0031628 W

6 dBm

0.0039811 W

7 dBm

0.0050119 W

8 dBm

0.0063096 W

9 dBm

0.0079433 W

10 dBm

0.01 W

20 dBm

0.1 W

30 dBm

1 W

40 dBm

10 W

50 dBm

100 W

In the next section, we will use the dBm to watts conversion calculator for converting between the two.

How to use the dBm to watts calculator

Now let us see how we can use the dBm to watts calculator to convert 50 dBm to watts.

  1. Using the drop-down menu, choose the conversion type as dBm to watts.

  2. Enter the power in dBm, i.e., 50 dBm.

  3. The tool will convert the power in dBm to power in watts, i.e., 100 watts. If you want a conversion from dBm to mW, use the drop-down menu to choose dBm to milliwatts as the conversion type.

  4. You can also use this calculator to convert from watts/milliwatts to dBm.

We also have a tool that converts signal distortion from percent to decibel and vice versa, so make sure you check out our total harmonic distortion calculator as well!


How do I convert dBm to watts?

To convert dBm to watts, follow the given instructions:

  1. Divide the power in dBm by 10.
  2. Calculate 10 to the power of the result from step 1.
  3. Now divide the value from step 2 by 1000, and you will get the value of power in watts.

What is the dBm equivalent for 1 watt?

30 dBm. Using the formula:

P(dBm) = 10 × log10(1000 × P(W)/1W),

we can calculate for 1 W:

P(dBm) = 10 × log10(1000 × 1W/1W) = 30 dBm.

How many dBm is 5 watts?

36.99 dBm. We know that the watts to dBm formula is:

P(dBm) = 10 × log10(P(W)/1W) +30.

Hence, we can write

P(dBm) = 10 × log10(5) + 30;


P(dBm) = 10 × 0.699 + 30 = 36.99.

What is 8 dBm in watts?

0.00631 watts. For converting 8 dBm to watts, we will use the formula:

P(W) = 1W × (10p(dBm)/10)/1000

  1. Calculating 10 raised to the power of 8/10 = 0.8, we get 6.31.

  2. Dividing the result by 1000, we will get the power in watts, i.e., 0.00631 watts.

Purnima Singh, PhD
🤔 Choose the conversion type!💡
Conversion type
dBm to watts
dBm to watts
Power in dBm
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