Enter two hCG blood values and this calculator computes the doubling time (or half-life), the actual percent change, and the projected 48-hour rise — then evaluates it against every major published threshold: the Barnhart 2016 level-stratified minimums (49/40/33%), the 53% any-level minimum (Barnhart 2004), the 35% floor still compatible with viable pregnancy (Seeber 2006, Morse 2012), and the UK NICE NG126 criteria (63% rise / 50% fall). Where the frameworks disagree, it says so honestly. Built by Amos Grünebaum, MD, Professor of Obstetrics and Gynecology. Explore hCG levels by week, the implantation timeline, when to test, and IVF betas after transfer.