Calculators
Pregnancy Week Calculator by hCG Level
Calculator
Enter your beta-hCG blood test result to instantly see which pregnancy weeks fall in its normal range, what to expect on ultrasound, and what the change between two measurements means.
What to know first:
An hCG test confirms that a pregnancy exists — it does not tell you which week you're in. The same result can occur at 6 weeks or at 12 weeks. This tool doesn't give you a single week; it shows the weeks your result is consistent with. The exact week is confirmed by ultrasound.
Beta-hCG (human chorionic gonadotropin) is a hormone secreted by the cells that will form the placenta, once the fertilized egg implants in the uterine wall. It can be measured in blood even before a missed period, which is why it's the earliest and most reliable way to confirm a pregnancy.
However, the hormone's level varies enormously between individuals. A few days' difference in implantation timing, a singleton versus a twin pregnancy, even the laboratory's own assay method can noticeably affect the result. Two healthy pregnancies at the same week can differ by more than 50-fold. What's more, hCG peaks around weeks 8–11 and then declines — so a given value can occur both while it's rising and while it's falling.
Reference ranges by week
hCG calculator
Enter your own result and tap "Calculate", or use the slider above.
Tap a week: the line moves to that week's typical value, and other weeks that match the same value light up too. On desktop, you can drag the line directly on the chart with your mouse.
| Pregnancy week | Beta-hCG (mIU/mL) | Range |
|---|---|---|
| Week 3 | 5 – 50 | mIU/mL |
| Week 4 | 5 – 426 | mIU/mL |
| Week 5 | 18 – 7,340 | mIU/mL |
| Week 6 | 1,080 – 56,500 | mIU/mL |
| Weeks 7–8 | 7,650 – 229,000 | mIU/mL |
| Weeks 9–12 | 25,700 – 288,000 | mIU/mL |
| Weeks 13–16 | 13,300 – 254,000 | mIU/mL |
| Weeks 17–24 | 4,060 – 165,400 | mIU/mL |
| Weeks 25–40 | 3,640 – 117,000 | mIU/mL |
The exact pregnancy week is determined by measuring the embryo on ultrasound (CRL). Base any time-sensitive decisions on the ultrasound result, not the blood value.
This tool is for information only; it does not diagnose or recommend treatment. Reference ranges vary between laboratories. Always discuss your result with your doctor.
The same result, weeks apart
The examples below show how a single blood result can be consistent with pregnancies that are weeks apart.
| hCG | A | B |
|---|---|---|
| 40,000 mIU/mL | Week 6 1,080 – 56,500 mIU/mL | Weeks 9–12 25,700 – 288,000 mIU/mL |
| 20,000 mIU/mL | Week 6 1,080 – 56,500 mIU/mL | Weeks 13–16 13,300 – 254,000 mIU/mL |
| 80,000 mIU/mL | Weeks 7–8 7,650 – 229,000 mIU/mL | Weeks 25–40 3,640 – 117,000 mIU/mL |
A pregnancy just becoming visible in the uterus and one nearing the end of the first trimester can give the same result.
Because hCG declines after its peak, a pregnancy in the second trimester can show as low a value as one in the early weeks.
This value fits almost any period from the first trimester to the third; on its own it tells you very little about the week.
Two measurements tell you more than one
In early pregnancy, how hCG changes matters as much as how high it is. In most healthy early pregnancies the value rises noticeably over 48 hours; research has shown that a rise of less than about 35% over 48 hours in this period may warrant further evaluation. As the value climbs, the rate of rise naturally slows — above 6,000 mIU/mL the doubling time lengthens, and that alone is not a cause for concern.
A slow rise, an unexpected fall, or a value that doesn't change at all calls for your doctor to evaluate you together with ultrasound, to investigate possibilities such as ectopic pregnancy or threatened miscarriage. If you enter a second result into the tool above, it will calculate the 48-hour rise rate and doubling time for you.
Ultrasound is what confirms the week
Blood test (beta-hCG)
- Confirms early on whether a pregnancy exists.
- Serial measurements give a sense of how the pregnancy is progressing.
- Does not show where the pregnancy is (inside the uterus or not) or which week it is.
Ultrasound
- Confirms the gestational sac is inside the uterus.
- Measures the embryo's crown-rump length (CRL) to pinpoint the week within a few days.
- Shows the heartbeat and the number of pregnancies.
On transvaginal ultrasound, a gestational sac usually becomes visible once hCG reaches roughly 1,500–3,500 mIU/mL. This threshold varies by equipment and by individual; not seeing a sac above this level may call for closer follow-up by your doctor. For time-sensitive decisions such as an elective termination, it's the ultrasound-determined week that matters — assuming you're "earlier than you think" based on a blood value alone can cost valuable time.
Frequently asked questions
Can my hCG value tell me exactly how many weeks pregnant I am?
No, not exactly. Each week's normal range is very wide and overlaps with neighboring weeks. This tool shows the weeks consistent with your result; your actual week is determined by ultrasound.
My hCG is high — does that mean twins?
Twin pregnancies can average a higher hCG, but a high value alone doesn't confirm twins. The number of pregnancies is only established by ultrasound.
How long should I wait between two tests?
Usually 48 hours, sometimes 72. Shorter intervals can be misleading due to lab-to-lab variation. If possible, have both tests done at the same laboratory.
At what value is hCG considered positive?
Most laboratories consider below 5 mIU/mL negative and above 25 mIU/mL positive. For values in between, retesting after 48 hours is recommended.
When does hCG return to zero after a pregnancy ends?
After a miscarriage or a termination, hCG declines gradually and, depending on the starting value, usually becomes negative within 2–6 weeks. Home tests may stay positive for a while during this time; follow-up is guided by your doctor.
Sources
- American College of Obstetricians and Gynecologists. Practice Bulletin No. 193: Tubal Ectopic Pregnancy. Obstet Gynecol. 2018.
- Barnhart KT, Guo W, Cary MS, et al. Differences in serum human chorionic gonadotropin rise in early pregnancy by race and value at presentation. Obstet Gynecol. 2016;128(3):504–511.
- World Health Organization. Abortion care guideline. Geneva: WHO; 2022.
Medical content reviewed by: Op. Dr. Şükrü Sanus, Obstetrician & Gynecologist · SoftCare Clinic
The information on this page is for general information only and does not replace an examination or your doctor's assessment.
Let's confirm your week with ultrasound
Bring your hCG result when you visit; after the examination we'll discuss your pregnancy week and next steps together.
References
- Symptomatic patients with an early viable intrauterine pregnancy: HCG curves redefined. Barnhart KT, et al. Obstetrics and Gynecology, 2004.
Medically reviewed by Op. Dr. Şükrü Sanus, Obstetrician & Gynecologist · Last medical review: