Enter the original power of the signal and the reduction into the calculator to determine the power of the signal after a 3dB reduction.

## 3Db Rule Formula

The following formula is used to calculate the signal power after a 3dB reduction.

P2 = P1 / (10^{(3/10)})

Variables:

- P2 is the power of the signal after the 3dB reduction (Watts)
- P1 is the original power of the signal (Watts)

To calculate the power of the signal after a 3dB reduction, divide the original power of the signal by 10 raised to the power of 3 divided by 10. This formula is derived from the definition of decibel, which is a logarithmic unit used to express the ratio of two values of a physical quantity. In this case, a decrease of 3dB represents a halving of the signal’s power.

## What is a 3Db Rule?

The 3dB rule is a standard rule in electronics and signal processing, stating that a signal has half its original power when its amplitude is reduced by approximately 30%. This is often used in the context of signal attenuation, bandwidth measurement, and frequency response, where a decrease of 3dB represents a halving of the signal’s power. The term “3dB” comes from the use of decibels (dB) as a logarithmic unit to express the ratio of two values of a physical quantity.

## How to Calculate 3Db Rule?

The following steps outline how to calculate the 3dB Rule.

- First, determine the original power of the signal (P1) in Watts.
- Next, calculate the power of the signal after the 3dB reduction (P2) using the formula: P2 = P1 / (10^(3/10)).
- Finally, calculate the 3dB Rule.
- After inserting the variables and calculating the result, check your answer with the calculator above.

**Example Problem : **

Use the following variables as an example problem to test your knowledge.

Original power of the signal (P1) = 100 Watts