Calculator Pregnancy
hCG doubling time calculator
In early pregnancy the trend in hCG matters far more than any single value. Enter two blood results and the time between them to see your doubling time and rate of rise.
Your hCG doubling time
0hours
By the numbers Context
What hCG doubling time means
Human chorionic gonadotropin (hCG) is the hormone a pregnancy produces, and it rises quickly in the early weeks. Because the normal range at any given week is very wide, doctors watch the trend rather than a single value: in a healthy early pregnancy, hCG typically doubles roughly every 48 to 72 hours until around 6 weeks, after which the rise naturally slows. This calculator takes two hCG results and the time between them and works out the doubling time and percentage increase.
It is important to hold this loosely. A slower-than-expected rise can have many explanations, and plenty of healthy pregnancies do not follow the textbook curve; equally, a “good” number is not a guarantee. hCG is only ever interpreted alongside how far along you are, an ultrasound, and your symptoms — and that interpretation belongs to your clinician. If you are worried about your levels, contact your care team rather than drawing conclusions from a number.
48–72 h
typical hCG doubling time in early pregnancy (before ~6 weeks)
Clinical
Very wide
the normal hCG range at every week of pregnancy
Clinical
The trend
what clinicians watch — not a single value
Clinical
Sources: standard early-pregnancy hCG monitoring guidance (e.g. ACOG / clinical references).
Frequently asked questions
How fast should hCG rise in early pregnancy?
In a typical early pregnancy, hCG roughly doubles every 48 to 72 hours until about 6 weeks, then rises more slowly. A rise of at least ~35% over 48 hours is often considered reassuring, but ranges are wide and only a clinician can interpret your numbers.
What is a good hCG level at 4 or 5 weeks?
The normal range is enormous at every week — for example, roughly 10–700+ mIU/mL around 4 weeks and hundreds to several thousand by 5 weeks. Because the spread is so wide, a single value means little; the trend between two tests is what matters.
What hCG level means a miscarriage is likely?
There is no single number that determines this. What raises concern is a pattern — hCG that falls, plateaus, or rises very slowly (well under ~35% in 48 hours) in early pregnancy. Even then it is not definitive, and it must be interpreted by a clinician alongside ultrasound. If you are worried, contact your care team.
How do you calculate hCG doubling time?
From two hCG values and the hours between them, using the formula: doubling time = time × ln(2) ÷ ln(second value ÷ first value). This calculator does the maths and also shows the percentage rise.
Can a home pregnancy test give me an hCG number?
No. Home urine tests only detect whether hCG is above a threshold (positive or negative). A numeric hCG value comes from a blood test (quantitative beta-hCG) ordered by a clinician.