hCG Doubling Time Calculator
Calculate how fast your hCG level is doubling between two blood tests — the number early-pregnancy monitoring watches most closely.
Doubling time
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Increase —
Typical early range —
Informational only — hCG trends must be interpreted by your healthcare provider alongside ultrasound.
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How it works
Doubling time = hours between tests × ln(2) ÷ ln(hCG₂ ÷ hCG₁)Frequently Asked Questions
What is a normal hCG doubling time?
In early pregnancy (below ~1,200 mIU/mL), hCG typically doubles every 48–72 hours; the pace naturally slows as levels rise, taking up to 96 hours above 6,000. A rise of at least 35% in 48 hours can still be normal.
My hCG isn't doubling — should I worry?
Slower-than-textbook rises still end in healthy pregnancies, especially at higher levels where doubling normally slows. Falling or plateauing levels need prompt medical review — only your provider can interpret your trend with ultrasound context.
Do high hCG numbers mean twins?
Sometimes — multiples often run higher — but single ranges are so wide that hCG alone can't tell. Ultrasound answers it definitively around 6–7 weeks.