HCG Calculator

Understanding HCG Levels in Early Pregnancy

This HCG calculator checks your beta-HCG level against normal reference ranges by week of pregnancy and calculates doubling time for two serial measurements. Human chorionic gonadotropin (HCG) is produced by placental cells beginning a few days after implantation — beta-HCG tests can detect levels as low as 1–5 mIU/mL, confirming pregnancy 8–10 days after conception.

In a normally progressing pregnancy, HCG levels double approximately every 48–72 hours during the first trimester, peak between 9–12 weeks (25,700–288,000 mIU/mL), then decline to a plateau for the rest of pregnancy. This predictable pattern makes serial HCG measurement one of the most important early pregnancy monitoring tools.

HCG Reference Ranges by Week of Pregnancy

The following ranges represent the 5th–95th percentile from clinical population data. Individual values vary widely — a single measurement within or outside these ranges is not diagnostic without clinical context:

• 3 weeks LMP: 5–50 mIU/mL
• 4 weeks LMP: 5–426 mIU/mL
• 5 weeks LMP: 18–7,340 mIU/mL
• 6 weeks LMP: 1,080–56,500 mIU/mL
• 7–8 weeks LMP: 7,650–229,000 mIU/mL
• 9–12 weeks LMP: 25,700–288,000 mIU/mL (peak)
• 13–16 weeks: 13,300–254,000 mIU/mL
• 17–24 weeks: 4,060–165,400 mIU/mL
• 25–40 weeks: 3,640–117,000 mIU/mL

HCG Doubling Time: What It Means

A single HCG value is rarely sufficient. The trend over time is far more informative. In early pregnancy (up to about 6 weeks), HCG should increase by at least 66% every 48 hours, equivalent to a doubling time of roughly 48–72 hours. As pregnancy progresses past 6 weeks, the rate of rise normally slows, with doubling times extending to 72–96 hours or longer.

For a dedicated doubling time calculation with interpretation, use the HCG doubling time calculator, which takes two dated measurements and computes the exact doubling time in hours.

When to Be Concerned About HCG Levels

Contact your healthcare provider if:

• HCG is not rising appropriately (less than 53% increase over 48 hours in early pregnancy)
• HCG is falling instead of rising
• HCG levels plateau or decline before reaching 9–12 weeks
• You have pelvic pain, shoulder pain, or heavy bleeding along with any HCG abnormality — these may indicate ectopic pregnancy requiring urgent evaluation

Factors That Affect HCG Interpretation

Several factors can cause HCG to fall outside the expected range even in healthy pregnancies. Twin or multiple pregnancies typically have HCG levels 30–50% higher than singleton pregnancies. Incorrect gestational age dating (especially irregular cycles) can make a normal level appear low or high — if you are unsure about your cycle timing, our period calculator can help estimate your last menstrual period and expected ovulation dates. Fertility treatments including HCG trigger shots can add exogenous HCG that persists for 10–14 days after injection, potentially causing false-positive readings.

HCG After IVF and Fertility Treatments

Women undergoing IVF typically have their first beta-HCG measured 9–11 days after embryo transfer. An HCG above 100 mIU/mL at this point is generally considered a positive result, though many fertility clinics use individualized thresholds based on embryo transfer day. The exogenous HCG trigger shot used to induce ovulation has a half-life of approximately 24–48 hours and is typically undetectable within 10–14 days, so it should not affect the test at standard post-transfer timing. For dedicated doubling time analysis, use our HCG doubling time calculator.

HCG and Gestational Trophoblastic Disease

Gestational trophoblastic disease (GTD) — including molar pregnancy and choriocarcinoma — produces abnormally elevated HCG levels, often in the tens of thousands even in the absence of a normal fetus. Molar pregnancies typically show HCG levels much higher than expected for gestational age, along with characteristic ultrasound findings. After treatment of GTD, serial HCG monitoring every 1–2 weeks is essential to confirm complete resolution. Rising or plateauing HCG after molar evacuation indicates persistent or malignant GTD requiring chemotherapy. GTD is one of the most chemotherapy-responsive cancers — cure rates exceed 95% even for metastatic disease.