hCG Doubling Calculator
Enter two hCG values and the hours between to get the doubling time and percent rise.
| Percent increase | — |
|---|---|
| Daily rise | — |
| First / second | — |
| Typical (early) | — |
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How the hCG Doubling Calculator Works
In early pregnancy the hormone hCG rises quickly, and how fast it doubles is one signal providers watch. Given two blood-test values and the hours between them, this calculator finds the doubling time using exponential growth — the hours multiplied by the natural log of 2, divided by the log of the ratio of the two values. It also shows the percent increase and the daily rate.
Early on, hCG commonly doubles every 30 to 72 hours, though normal ranges vary and slowing is expected as levels get high. A single pair of numbers doesn’t tell the whole story — only your provider can interpret it alongside your history and ultrasound.
doubling time = hours × ln(2) ÷ ln(second ÷ first)
Note: an estimate for general guidance, not medical advice. Your doctor or midwife knows your situation best.
Frequently Asked Questions
How fast should hCG rise?
In early pregnancy it often doubles every 30–72 hours, then slows as levels climb. Ranges vary widely between healthy pregnancies.
How do I calculate hCG doubling time?
From two values and the time between them, using exponential growth. This calculator does it and shows the percent rise.
Should I worry if it doubles slowly?
Not necessarily — normal patterns vary and slowing is expected at higher levels. Always discuss results with your provider rather than self-interpreting.