hCG Levels Calculator — Check by Week & Doubling Time
Compare a blood hCG result against weekly reference ranges, estimate doubling time from two serial draws, and browse the full hCG reference chart.
Estimate only — not medical advice. hCG numbers alone cannot diagnose a healthy or unhealthy pregnancy. Always discuss your results with your clinician.
Reference checker
Enter your blood hCG result and how many weeks pregnant you are (from the first day of your last period). The tool compares it against the published weekly reference band.
Doubling time calculator
Enter two quantitative (beta) hCG blood results taken at different times — clinicians usually draw them 48–72 hours apart. The tool computes the doubling time and the 48-hour rise percentage.
The doubling rules below apply to early pregnancy (roughly the first 6–8 weeks). After hCG peaks around weeks 8–11, rising slows, plateaus, then falls — a longer doubling time then is expected.
hCG reference chart (weeks 3–40)
Guideline reference bands from the American Pregnancy Association hCG levels chart, in mIU/mL. Every person's levels differ — the trend across serial draws matters more than any single number.
Week
Reference band (mIU/mL)
How this calculator works
Reference checker. Each weekly band is a guideline range from the American Pregnancy Association hCG levels chart (mIU/mL): week 3: 5–50; week 4: 5–426; week 5: 18–7,340; week 6: 1,080–56,500; weeks 7–8: 7,650–229,000; weeks 9–12: 25,700–288,000; weeks 13–16: 13,300–254,000; weeks 17–24: 4,060–165,400; weeks 25–40: 3,640–117,000. Your value is classified as below, within, or above the band (bounds inclusive).
Doubling time. Doubling time = hours × ln(2) / ln(second ÷ first). The 48-hour rise = (second ÷ first)^(48 ÷ hours) − 1. In early pregnancy hCG typically doubles every 48–72 hours, slowing to about every 96 hours as levels climb (American Pregnancy Association). Research on viable early pregnancies (Barnhart et al., Obstetrics & Gynecology 2004) found the slowest rise still compatible with viability is 53% in 48 hours — equal to a doubling time of about 78 hours. A rise below that minimum does not diagnose a problem, but it is the usual threshold clinicians use to look closer.
Honest limits. A single hCG number cannot confirm or rule out a healthy pregnancy: timing of ovulation, lab methods, and person-to-person variation all shift values widely. Trend across serial draws plus ultrasound is what clinicians rely on.
Frequently asked questions
What are normal hCG levels by week of pregnancy?
The American Pregnancy Association publishes this guideline chart (mIU/mL): week 3: 5–50; week 4: 5–426; week 5: 18–7,340; week 6: 1,080–56,500; weeks 7–8: 7,650–229,000; weeks 9–12: 25,700–288,000; weeks 13–16: 13,300–254,000; weeks 17–24: 4,060–165,400; weeks 25–40: 3,640–117,000. These are wide guideline bands, not precise targets — healthy pregnancies land anywhere inside them.
How fast should hCG double in early pregnancy?
In early pregnancy hCG typically doubles every 48–72 hours, slowing to about every 96 hours as levels get higher. Research on viable early pregnancies (Barnhart et al., 2004) found the slowest rise still compatible with viability is 53% in 48 hours, which equals a doubling time of about 78 hours. Slower than that does not diagnose a problem, but clinicians usually investigate further.
How is this different from a false negative pregnancy test calculator?
This tool compares your blood hCG against weekly reference ranges and computes doubling time from two serial draws — it answers “is my level in the normal range?” and “how fast is it rising?”. Our false negative pregnancy test calculator answers a different question: the probability that a urine test misses a pregnancy at a given day past ovulation, using a published statistical model. Use that tool when you got a negative test but might still be pregnant; use this one once you have blood hCG numbers to interpret.
Can a single hCG level tell me if my pregnancy is viable?
No. A single hCG value cannot confirm or rule out a viable pregnancy — the American Pregnancy Association explicitly warns against over-interpreting one number, and ultrasound after 5–6 weeks is more accurate. Clinicians look at the trend across serial draws taken 48–72 hours apart, plus ultrasound findings.
My hCG is below the reference range — should I worry?
Not necessarily. A lower-than-expected value often just means ovulation or dating is off by a few days, since hCG rises steeply in early weeks. It can also happen in a completely healthy pregnancy. The usual next step is a repeat blood draw in 48–72 hours to check the trend — discuss it with your clinician rather than diagnosing from one number.
My hCG is above the reference range — does that mean twins?
Not necessarily. Dating differences and normal person-to-person variation are the most common reasons. Higher levels can occur with multiples or molar pregnancy, but the range alone cannot tell you which. A repeat draw and an ultrasound are how clinicians sort this out.
Do hCG levels keep rising through the whole pregnancy?
No. hCG climbs steeply in the first weeks, peaks around weeks 8–11 (the reference band peaks at 25,700–288,000 mIU/mL for weeks 9–12), then declines and levels off for the rest of the pregnancy. A falling level after the peak is the expected pattern, not a warning sign.
Why does my lab's reference range differ from this chart?
Reference ranges vary between laboratories because assays are calibrated differently — this is expected and normal. Your lab's own range on your result sheet is the one that applies to your sample. This tool's chart is the American Pregnancy Association guideline for orientation; when in doubt, compare your result against the range printed by your lab.
Should I track hCG with a blood test or a urine test?
Doubling-time tracking needs quantitative blood (beta) hCG tests drawn at a lab — urine home tests only give positive/negative (or faint/dark lines) and cannot measure the rise. Blood tests detect hCG from about 5 mIU/mL; urine tests become reliable around the missed period. If your clinician ordered serial betas, keep using the same lab so the numbers are comparable.
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