Enter either the hCG level or the gestational age into the calculator to show an approximate reference range for the other value. hCG varies enormously between normal pregnancies, so ultrasound is the most accurate way to date a pregnancy.
Medical disclaimer: This calculator uses published quantitative blood (serum) hCG reference ranges and provides only an approximate range; it is not medical advice and cannot confirm viability, rule out ectopic pregnancy, or diagnose miscarriage. Reference ranges vary by lab/assay—use ultrasound and clinician guidance for dating and interpretation. Seek urgent medical care for heavy bleeding, severe or one-sided abdominal/pelvic pain, shoulder pain, dizziness/fainting, or severe worsening pain.
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HCG to Weeks Table (UCSF Health reference ranges; serum, mIU/mL)
| Gestational age (weeks) | Lower limit (mIU/mL) | Upper limit (mIU/mL) |
|---|---|---|
| 3 weeks | 5 | 72 |
| 4 weeks | 10 | 708 |
| 5 weeks | 217 | 8 245 |
| 6 weeks | 152 | 32 177 |
| 7 weeks | 4 059 | 153 767 |
| 8 weeks | 31 366 | 149 094 |
| 9 weeks | 59 109 | 135 901 |
| 10 weeks | 44 186 | 170 409 |
| 12 weeks | 27 107 | 201 165 |
| 14 weeks | 24 302 | 93 646 |
| 15 weeks | 12 540 | 69 747 |
| 16 weeks | 8 904 | 55 332 |
| 17 weeks | 8 240 | 51 793 |
| 18 weeks | 9 649 | 55 271 |
What Is HCG to Weeks?
HCG to weeks refers to the relationship between the level of human chorionic gonadotropin (hCG) and gestational age. hCG is a hormone produced by the developing placenta after implantation, and it can be detected in both urine and blood. In early pregnancy, hCG often rises rapidly (commonly increasing roughly every 48–72 hours during the first few weeks), then the rate of increase slows, and levels typically peak around about 8–10 weeks of gestation. Because hCG ranges overlap heavily from week to week and vary by lab and by person, a single hCG value cannot accurately date a pregnancy; ultrasound is the preferred method for pregnancy dating.
How to Calculate HCG to Weeks?
The following steps outline a practical way to estimate a rough gestational-age range from an hCG result using published reference ranges (not a precise mathematical formula).
- Obtain a quantitative hCG blood test result (typically reported as mIU/mL; IU/L is numerically equivalent).
- Compare the hCG value to a reference table of typical ranges by gestational week (such as the UCSF Health ranges shown above).
- If the value falls into more than one week’s range (common), report a week range rather than a single week.
- For pregnancy assessment, interpret hCG with symptoms and (when appropriate) repeat testing to evaluate the trend; the rate of rise is not constant and varies widely.
- Confirm gestational age with ultrasound for the most reliable dating.
Example Problem:
Use the following variables as an example problem to test your knowledge.
HCG (mIU/mL) = 500
GA (gestational age in weeks) ≈ 4–5 weeks (500 falls within both the 4-week and 5-week reference ranges in the table).
