Our Sizing Chart board gives measurment’s information of the pants sizes, so you will have to calculate the size of your own pants, not the size of your physical body.
The best to get the exact size you need, would be to take the measurement of one of your pants that fit you correctly.
So you are going to take the measurement of your pants from the top left side to the top right side (upper part of the pants, so at the belt area)
To do so, put your pants on a flat surface and do the measure starting from the inside of the pants (not from the outside as we dont want to get the thickness of the fabric in the total waist calculation), and figure out the available space for your body to fit in perfectly.
Here is a photo showing you how to get the correct measurements.