In about 85% of normal pregnancies, the hCG level will double every 48 – 72 hours.
As you get further along in pregnancy and the hCG level gets higher, the time it takes to double can increase to aboutevery96hours.
Caution must be used in making too much of hCG numbers. A normal pregnancy may have low hCG levels and result in a perfectly healthy baby.
Source: American Pregnancy Association
How to use the hCG Calculator:
Input your first hCG level, your second hCG level and the number of days in between tests then calculate.