hCG Calculator (Doubling Time)
Compare two hCG blood tests to find the percent rise, the doubling time and whether the rise matches what is typical in early pregnancy. Example: hCG of 200 rising to 450 in 48 hours is a 125% increase with a doubling time of about 41 hours.
Show steps
How to use the hCG Calculator (Doubling Time)
- Enter the values in the fields.
- Press Calculate to see the result with the steps shown.
Formula and method
Percent rise = (second – first) / first x 100. Doubling time = hours x ln 2 / ln(second / first). Typical minimum 48-hour rise: 49% if the first hCG is under 1,500, 40% for 1,500 to 3,000, 33% above 3,000.
Typical hCG levels by week of pregnancy (mIU/mL)
| Weeks since LMP | Range |
|---|---|
| 3 | 5 to 50 |
| 4 | 5 to 426 |
| 5 | 18 to 7,340 |
| 6 | 1,080 to 56,500 |
| 7 to 8 | 7,650 to 229,000 |
| 9 to 12 | 25,700 to 288,000 |
Minimum expected 48-hour rise
| Starting hCG | Minimum rise in 48 hours |
|---|---|
| Below 1,500 | 49% |
| 1,500 to 3,000 | 40% |
| Above 3,000 | 33% |
Rise in 48 hours and doubling time
Rise in 48 hours,Doubling time,33%,117 hours,40%,99 hours,49%,83 hours,100%,48 hours,150%,36 hours
What the numbers can and cannot tell you
Levels vary enormously between healthy pregnancies, and a single number cannot predict outcome. After about 1,500 to 2,000 mIU/mL an ultrasound should show a gestational sac. This calculator is for education and is not medical advice. Your own doctor, midwife or pediatrician should guide decisions about your care.
Frequently asked questions
How fast should hCG double?
In early pregnancy, about every 48 to 72 hours.
What is a normal hCG rise?
At least 49% in 48 hours if the starting level is under 1,500.
Does slow hCG mean miscarriage?
Not necessarily; ask your clinician.
When does hCG peak?
Around 8 to 11 weeks.
What if hCG is falling?
This can indicate a pregnancy loss; contact your clinician.
Why compare two tests from the same lab?
Different labs use different assays.
Sources
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