dBm to Watt Calculator

Use this tool to convert dBm (deciBel milliwatt) to Watt.

Use the unit selector to switch between Watt, milliwatt, microwatt and nanowatt.

🔁 Watt to dBm

Formula

P_Watt = 10^{((P_dBm – 30)/10)}

where

• P_dBm is the power in dBm
• P_Watt is the power in Watt

Example Calculations

The default value used in the calculator above is 1 dBm.

1 dBm is equivalent to 0.00126 Watt or 1.26 milliwatt.

The following two values are very common base line values from which others are calculated:

• 30 dBm is equivalent to 1 Watt
• 0 dBm is equivalent to 1 milliwatt

Background

dBm stands for deciBel referenced to one milliwatt. It is commonly used by RF engineers in the context of absolute power levels associated with various components such as filters, amplifiers, splitters and more.

People often confuse dBm with dB. dB or deciBel has no units and represents the logarithm of a power or amplitude ratio. This post explains the relationship between dBm and dB.

Watt is a unit of power or radiant flux. It is equivalent to 1 joule per second or 1 kg⋅m²⋅s⁻³

Note: Watt is a unit of power in the International System of Units (SI). dBm however is not in the International System of Units.

Where is Watt used?

Watt is used in electrical engineering power calculations. Its use is more widespread than dBm. Watt is used in audio, radio frequency and wireless, power systems and more.

Where is dBm used?

dBm is used in link budgets, antenna range computation, noise floor calculations and more. It’s easy to work with both dBm and dB as they require simple addition and subtraction. By comparison, working with Watt involves a larger range of number values that have to be multiplied and divided.

We also use dBm with our communication technologies. For instance, Wi-Fi signal strength – also known as RSSI (Received Signal Strength Indicator) is measured in terms of dBm. The higher the dBm value, the better the signal. The dBm value relates directly to Internet speed.

dBm values for signal strength in 4G, 5G and Wi-Fi measured on a phone or tablet are negative. It might be confusing at first, but the more negative the value, the weaker the signal. For instance, -85 dBm represents a weaker signal relative to -45 dBm.

Why convert from dBm to Watt?

The maximum input to an RF module can sometimes be specified in Watt. If the output from a circuit that feeds the module is specified in dBm, then it would make sense to convert this value to Watt to check if it’s under the limit.

Another instance is when calculating the Power Added Efficiency. Defined as the ratio of the difference between the output and input power to the DC power consumed. In this case, the entire calculation is performed in Watt with the formula below:

PAE = 100*(P_RFOUT – P_RFIN)/P_DC

In this case each of these quantities if specified in dBm, should be converted to Watt before using the formula.

dBm to Watt Formula

P_Watt=(10^(P_dBm/10))/1000

dBm to Watt Table

The following table shows dBm and equivalent Watt value

dBm to Watt Excel Calculator

To convert from dBm to Watt, use the following formula in excel.

Watt=(10^(dBm/10))/1000

References

• dBm on Wikipedia
• Watt on Wikipedia