hCG Doubling Time Calculator
Calculate hCG doubling time and the percentage rise between two blood test results taken hours or days apart in early pregnancy.
For general information only — not medical advice. Results are estimates; talk to a doctor or qualified health professional about your own health.
How to use
- 1Enter your first and second hCG results.
- 2Enter the hours between the two blood draws (48 hours is typical).
How it's calculated
Doubling time = hours × ln(2) ÷ ln(second ÷ first). Rise over 48 h = (second ÷ first)^(48 ÷ hours) − 1.
Frequently asked questions
What's a normal hCG rise?
In early viable pregnancies hCG usually rises at least about 35–50% in 48 hours, often doubling every 2–3 days. The rise slows after about 6 weeks.
Does a slow rise mean something is wrong?
Not necessarily. Your doctor interprets hCG trends alongside ultrasound and symptoms.
Can I compare results from different labs?
Ideally use the same lab — methods vary slightly.