To calculate the number of pounds you're losing (or gaining) per week in a given month, subtract the final trend number for the month from the initial trend number, then divide by 4 to get weekly weight loss (or gain). For example, if on the first of the month the trend entry was 167 and on the last day of the month it stood at 160, you lost a total of 7 pounds that month. The loss per week is then 7/4, or 1.75 pounds.