Get all the dates associated with your pregnancy! Beta hCG Doubling Calculator Calculate the doubling time of two beta hCG test results. Pregnancy Weight Calculator Calculate your pre-pregnancy body mass index to determine what your target weight range should be for this pregnancy. By 6 to 7 weeks beta hCG levels may take as long as 3 1/2 days to double. hCG normally reaches a peak level at about 8 to 10 weeks and then declines for the remainder of the pregnancy. The beta hCG level for a successful intrauterine pregnancy should be expected to increase by at least 35% in two days [Morse and coworkers (2012)]. A positive pregnancy test looks for levels above 25 mIU/ml. As you can see from the chart, normal exists as a relative term. In the early stages of your pregnancy it’s more important that your normal beta hcg levels or numbers continually increase, rather than always being at the higher end of the range.