The following are some formulae to calculate the required bandwidth for many kinds of common modulation techniques:
Amplitude Modulation: 2 * Signal Frequency
Single Sideband Modulation: 1 * Signal Frequency
Vestigial Sideband Modulation: 1.20 to 1.30 * Signal Frequency
Narrowband Frequency Modulation: 2 * Signal Frequency
Wideband Frequency Modulation: 2 * Modulation Ratio * Signal Frequency
Pulse Amplitude Modulation: 0.5 * Pulse Frequency
From this, it can be seen that pulse amplitude modulation is the most bandwidth efficient. However, it cannot carry analog data. Single sideband modulation is the most bandwidth efficient for analog data, and wideband frequency modulation is the least. Even though it uses a lot of bandwidth, wideband frequency modulation has superior noise resistance, making it a good choice for some applications.