# How to use the PADI RDP Table

One of the most important things when answering questions with the RDP table, like the ERDPml, is to follow a methodical approach. Draw out a dive diagram, fill in the numbers from the question and then work the answer.

The RDP table will, in many cases, give different answers to the same question calculated using the ERDPml. The reason for this is that the table has columns for 35ft, 40ft, 50ft, 60ft and so on up to 140ft. The ERDPml has columns that only jump in five foot increments, 35ft, 40ft, 45ft, 50ft, 55ft and so on. This means that there is less rounding when using the ERDPml giving lower pressure groups or longer dives or shorter surface intervals on some dives.

Below i have laid out the different ways the RDP table can be used, and the different types of questions you may be asked. It is done by just giving an example question with a video to show how the answer can be calculated. At the bottom is a quiz for you to test what you have learned. At the end of the quiz you will be directed to a page that contains videos showing how to calculate the answers.