How to calculate class-D's efficiency?

Basically, almost all the audio PA datasheet will have the  efficiency VS outtput power figure.

For example, in TPA3124 datasheet, you can find the diagram figure 16.

It is generally provided in datasheet about efficiency  waveform with different outpower, if you need to know how to measure it ,please refer to the below app notes about the guideline for measuring the audio power amplifier performance:

www.ti.com/.../sloa068.pdf

attached class D test, that have how to calculate.

Calculate efficiency is very difficult at the class-D. PCB layout and induction...are very important for the efficiency. So, in first design, please see datasheet. If you are veteran, history is very important for your calculate.

Of coures, I have seen it, it was just a result. But, what I want to get is the calculate formula, then I can use the formula to improve the efficiency. Thanks!

To get high efficiency, most rely on the select device. and devide working conditioning.

Maybe you more conceit output power VS power consumption, that are not easy calculate form a format.