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hCG Level Calculator

Check your hCG level against reference ranges, calculate doubling time between draws, and project your first-trimester trajectory.

Your hCG Level

Normal: 48–72h doubling <6k Peak: weeks 9–11
Your hCG Level
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Enter a value above
LOW
NORMAL
HIGH
Within normal range
Gestational Age
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Expected Range
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Est. Doubling Time
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Status
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Percentile (est.)
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hCG Peak
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This calculator is informational only. hCG alone cannot diagnose a complication. Always discuss results with your healthcare provider.

Two-Draw Comparison

DT = hrs × ln(2) / ln(hCG2/hCG1)
Your Doubling Time
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Expected Range
48–72 hrs
% Change
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Rate
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Enter two hCG values with dates to see analysis.

Reading History Log

Track multiple readings over time. Data is stored in your browser.

DatehCG (mIU/mL)WeekDoubling

Projection Settings

Rise: ~2x every 48–72h Peak: wk 9–11 Then declines ~15%/wk

Projected Levels by Week

WeekRange MinRange MaxYour ProjectedIn Range?

Ultrasound Milestones

How to Use This Calculator

1

Enter Your hCG Level

Input your hCG blood test result and gestational age (weeks + days or DPO) to see where you fall in the reference range.

2

Analyze Doubling Time

Enter two draws with dates. The calculator computes actual doubling time and compares it to the expected 48–72 hour range.

3

Project Your Trajectory

See how your hCG may progress through the first trimester, with normal range bands and key ultrasound milestones.

Formula & Methodology

Doubling Time

Doubling Time = (Hours Between Tests × ln(2)) / ln(Second hCG / First hCG)

Normal doubling time in early pregnancy is 48–72 hours for hCG levels under 6,000 mIU/mL. Above 6,000, doubling slows to 72–96 hours.

Percentile Estimate

Percentile = (ln(hCG) − ln(min)) / (ln(max) − ln(min)) × 100

Uses a logarithmic scale since hCG ranges span several orders of magnitude within each gestational week.

About this calculation · Accuracy & Methodology

Key Terms

hCG (Human Chorionic Gonadotropin)
A hormone produced by the placenta after implantation. Detected by pregnancy tests; levels rise rapidly in early pregnancy, peak around weeks 9–11, then gradually decline.
Doubling Time
The time for hCG levels to double. In early viable pregnancies, this is typically 48–72 hours when hCG is below 6,000 mIU/mL.
Gestational Age
Pregnancy duration counted from the first day of the last menstrual period (LMP). Two weeks ahead of conception age.
DPO (Days Past Ovulation)
Count of days since ovulation occurred. Add 14 days to convert DPO to approximate gestational age.
Ectopic Pregnancy
A pregnancy outside the uterus, often indicated by abnormally slow hCG rise (doubling time over 72 hours) combined with ultrasound findings.
Discriminatory Zone
The hCG level (typically 1,500–2,000 mIU/mL) above which a gestational sac should be visible on transvaginal ultrasound.

Real-World Examples

Example 1

Normal Early Progression

Day 1: hCG = 120 mIU/mL. Day 3: hCG = 260 mIU/mL (48 hours later).

Doubling time = 43 hours. Within normal 48–72h range. hCG is rising appropriately.

Example 2

Slow Rise Concern

Day 1: hCG = 200. Day 5: hCG = 310 (96 hours later).

Doubling time = 148 hours. Significantly slower than expected. Ultrasound evaluation recommended.

Example 3

Possible Multiples

Day 1: hCG = 400. Day 3: hCG = 1,100 (48 hours later).

Doubling time = 32 hours. Very fast rise may suggest twins. Ultrasound will confirm.

Understanding hCG Levels in Early Pregnancy

The hCG Curve

In a viable early pregnancy, hCG typically doubles every 48–72 hours when levels are below 6,000 mIU/mL. Above 6,000, doubling slows to 72–96 hours. hCG peaks between weeks 8–11 (often reaching 100,000–200,000 mIU/mL) and then gradually declines for the remainder of pregnancy, plateauing around 20,000–50,000 in the second trimester.

When Doubling Time Is Abnormal

A doubling time over 72 hours (when hCG is under 6,000) may indicate ectopic pregnancy, impending miscarriage, or simply measurement variation. A single slow result is not diagnostic — trends over multiple draws matter more. About 15% of normal pregnancies have slower-than-expected hCG rise.

The Discriminatory Zone

When hCG reaches 1,500–2,000 mIU/mL (the "discriminatory zone"), a gestational sac should be visible on transvaginal ultrasound. If nothing is seen at this level, ectopic pregnancy must be excluded. By 7,500 mIU/mL, a yolk sac is typically visible, and fetal heartbeat detection becomes possible around 10,000–20,000 mIU/mL.

Limitations

hCG levels vary enormously between normal pregnancies. A single value cannot determine viability. Doubling time is more meaningful than absolute numbers. This calculator provides reference ranges from peer-reviewed medical literature but should never replace clinical evaluation.

Frequently Asked Questions

What is a normal hCG doubling time?

In early pregnancy (before 6 weeks), hCG typically doubles every 48–72 hours. After hCG reaches about 6,000 mIU/mL, the doubling rate slows to 72–96 hours. By 9–11 weeks, hCG peaks and then gradually declines for the remainder of pregnancy.

Should I worry if my hCG is rising slowly?

A single slow rise does not necessarily indicate a problem. Many factors affect hCG levels including measurement timing, lab variation, and individual pregnancy differences. Your provider will typically order serial draws 48–72 hours apart and consider the overall trend alongside ultrasound findings.

Can hCG levels predict twins?

Higher-than-average hCG levels and very fast doubling times (under 48 hours) can sometimes indicate multiples, but this is not reliable for diagnosis. Some singletons have very high hCG, and some twin pregnancies have normal-range levels. Ultrasound is the definitive way to confirm.

What does declining hCG mean?

After 9–11 weeks, hCG naturally declines — this is completely normal. However, if hCG drops in early pregnancy (before 8 weeks), it may indicate miscarriage or ectopic pregnancy. Your provider will interpret declining levels in context with symptoms and ultrasound.

What is the discriminatory zone?

The discriminatory zone is the hCG level (typically 1,500–2,000 mIU/mL for transvaginal ultrasound) above which a gestational sac should be visible. If hCG is above this level and nothing is seen on ultrasound, ectopic pregnancy must be considered.

How accurate is this calculator?

This calculator uses standard reference ranges from peer-reviewed medical literature. However, hCG reference ranges vary between laboratories and individual pregnancies. This tool is for informational purposes only and should never replace advice from your healthcare provider.