This tool calculates the bandwidth of a Frequency Modulation (FM) signal. It also finds the modulation index.

**Formula**

According to Carson’s rule states approximately 98% of the power of a frequency-modulated signal lies within a bandwidth given by the formula:

**B _{T} = 2*(Δf + f_{m})**

where

**Δf**is the peak deviation of the instantaneous frequency from the carrier center frequency**f**_{m}is the highest frequency in the modulating signal

the modulation index ** β** is given by

**Δf**/

**f**

_{m}

**Example Calculation**

A 5 kHz peak deviation of a 10 kHz audio signal results in a modulation index of 0.50 and a FM bandwidth of 30 kHz.

**FM Calculators**

These two calculators provide insight into the performance of FM transmitters and receivers

**References**

[1] Carson’s Rule on Wikipedia