CalculatorsPregnancy tracking

hCG Doubling Time Calculator

Calculate the mathematical change and estimated doubling time between two quantitative blood hCG results.

Your details

Enter only the information needed for this estimate.

Enter the quantitative result exactly as reported by the same laboratory unit. (IU/L or mIU/mL)

Use the blood collection time when available.

Use the same unit as the first result. (IU/L or mIU/mL)

The second sample must have been collected after the first.

Calculator entries stay in this browser session to produce this result. This tool does not save them in browser storage.

Complete the fields and select “Calculate hCG change” to see your estimate.

How the calculation works

The calculator uses the elapsed time and proportional change between two positive quantitative hCG values. It reports a mathematical doubling time when the second value is higher.

A trend is only one part of an assessment. Symptoms, gestational timing, ultrasound findings, additional blood tests, and laboratory variation can all matter.

How hCG is used in care

Clinicians may repeat hCG testing when the location or progression of an early pregnancy is uncertain. Guidance does not support using one value, or a calculator result alone, to decide whether a pregnancy is developing normally.

Use the follow-up interval and next steps given by the clinician or fertility clinic that ordered the tests.

Limits of this estimate

  • Results from different laboratories or different measurement units may not be directly comparable.
  • A faster or slower calculated change does not by itself establish pregnancy viability or location.
  • This tool is not designed for urine test lines, home-test darkness, or qualitative positive and negative results.

Common questions

How should I use this estimate?

Use it as a planning starting point, then compare it with your own experience and any guidance from a qualified health professional.

Is this medical advice?

This calculator performs an educational mathematical comparison only. It does not assess pregnancy viability or location, diagnose miscarriage or ectopic pregnancy, or replace urgent or planned medical care.

What happens to what I enter?

The calculator uses the values in your current browser session to produce the result. It does not save them in browser storage.