How to Use the Calculator
Put the known parameter in the leftmost column and it will calculate all other fields for you.
For example, If you are knowing Average value and want to calculate other three values.
Now you can enter an average value in the first column third row. After this press the calculate button and you will be able to see Peak, RMS and P-P in next three columns of the third row.
The theory of Sine waveform and all four parameters can be technically nutshelled in this graphic: