hCG Calculator
Compare levels. Understand the change.
Enter two or more hCG blood-test results to calculate doubling time
and percentage change, with a chart of your results.
How are my
hCG levels changing?
Enter results in the same units, from oldest to newest. mIU/mL and IU/L are numerically equivalent.
Your hCG results, in one place.
Add at least two results.
Your changes and chart will appear here.
The 48-hour value is a mathematical normalisation, not a prediction of a future blood result. No required doubling time or “normal” threshold is shown.
hCG doubling time,
explained.
How do I use the hCG calculator?
Enter at least two blood-test results from oldest to newest, including the exact date and time. Use the same units and a consistent time-zone offset. mIU/mL and IU/L are numerically equivalent.
How is hCG doubling time calculated?
For rising values: doubling time = elapsed hours × ln(2) ÷ ln(last result ÷ first result). This describes the rate of change between the entered results; it is not a prediction of the next test.
What is the 48-hour hCG rise?
The calculator mathematically rescales the change to a 48-hour interval: ((last ÷ first)^(48 ÷ elapsed hours) − 1) × 100. If your tests were not exactly 48 hours apart, this is a normalised comparison rather than an observed 48-hour blood result.
Do hCG levels have to double every 48 hours?
There is no single doubling-time rule that confirms a healthy pregnancy. Interpretation depends on the starting level, pregnancy timing, symptoms, ultrasound and other clinical findings. Discuss results with your clinician.
Can hCG levels tell me if I am having twins or an ectopic pregnancy?
This calculator cannot predict twins, confirm viability or rule out an ectopic pregnancy. Urgent symptoms need medical assessment even when hCG is rising.
Why is no doubling time shown when hCG falls?
A falling or unchanged value has no positive doubling time in this calculation. The percentage change is still shown. Your clinician should assess what that change means for you.
Sources: ACOG: estimating the due date · NHS: hCG testing