★ PROVEN TRAFFIC TOPIC · HEALTH · PREGNANCY
Medical disclaimer: this page is for education only and is not medical advice. A single pair of hCG values cannot diagnose a viable pregnancy, a miscarriage, or an ectopic pregnancy, and this calculator must never replace your clinician's judgment, an ultrasound, or repeat testing. At the defaults — 500 mIU/mL rising to 1,100 mIU/mL over 48 hours — the doubling time is 42.2 hours and the rise is +120%, a rise in the expected range for a viable early pregnancy. If your numbers look different, read the bands below and call your clinician rather than deciding anything from this page alone.
Educational only — not medical advice. Enter two quantitative (beta) hCG blood results and the hours between the blood draws. Doubling time is hours times ln(2) divided by ln(second divided by first); the rise is (second divided by first minus 1) times 100. Home urine pregnancy tests cannot be used here — they give lines, not numbers, and their darkness does not track hCG reliably.
Expected range: a rise of about 53% or more in 48 hours is commonly expected in a viable early pregnancy, with a doubling time at or under about 60 hours on this page's flag. Slower rise: a rise below about 53% in 48 hours, or a doubling time well past about 60 hours, is slower than usually expected and needs clinical follow-up — it can occur in a healthy pregnancy that is earlier than dated, in a miscarriage, or in an ectopic pregnancy, and blood values alone cannot tell those apart. Falling: any fall in hCG also needs clinical follow-up. None of these bands is a diagnosis. Clinicians interpret hCG together with ultrasound findings, symptoms, and repeat tests, and they — not this page — decide what happens next. If you have bleeding, severe pain, dizziness, or shoulder-tip pain, seek urgent care rather than waiting for another blood test.
Setup: first hCG 500 mIU/mL, second hCG 1,100 mIU/mL, 48 hours apart.
Line 1 — the ratio. 1,100 ÷ 500 = 2.20.
Line 2 — the rise. (2.20 − 1) × 100 = +120% over 48 hours, well above the roughly 53% floor.
Line 3 — the doubling time. 48 × ln(2) ÷ ln(2.20) = 48 × 0.6931 ÷ 0.7885 = 42.2 hours.
Line 4 — the band. Rise above 53% and doubling time under about 60 hours: rise in the expected range for a viable early pregnancy — reassuring as arithmetic, and still not a diagnosis.
Ratio 800 ÷ 500 = 1.60, so the rise is +60%, which clears the 53% floor — but the doubling time is 48 × 0.6931 ÷ ln(1.60) = 70.8 hours, well past the 60-hour flag, so this page calls it a slow rise. That tension is the point: one rule alone can mislead, which is why clinicians watch the trend over several tests instead of judging one pair. A single slow pair is a reason to follow up, not a verdict.
Ratio 400 ÷ 500 = 0.80, so the rise is −20%: the level fell, and no doubling time applies at all — a falling number cannot double. Falling hCG in early pregnancy most often accompanies a pregnancy that is ending, and it needs prompt clinical follow-up to confirm what is happening and to rule out an ectopic pregnancy. Do not wait for a third test on your own initiative; call your clinician.
Ratio 2,000 ÷ 1,000 = 2.00, so the rise is +100% and the doubling time is exactly 48.0 hours (48 × ln(2) ÷ ln(2) = 48). This is the textbook picture people mean by “doubling every two days,” and it sits squarely in the expected range. Note that real pregnancies rarely double this neatly: values near this picture are normal, and small departures from it are not, by themselves, alarming.
Ranges vary by lab and assay, and the same blood sample can read differently at different laboratories. The table below gives commonly published approximate ranges in mIU/mL for singleton pregnancies, counted from the last menstrual period. A value inside a range does not confirm a healthy pregnancy, and a value outside a range does not prove a problem — dating can be off by a week, twins raise hCG, and assays differ. Compare your result only against your own lab's reference range, printed on your report.
| Weeks pregnant | Approximate hCG range (mIU/mL) |
|---|---|
| 3 weeks | 5 – 50 |
| 4 weeks | 5 – 426 |
| 5 weeks | 18 – 7,340 |
| 6 weeks | 1,080 – 56,500 |
| 7 – 8 weeks | 7,650 – 229,000 |
| 9 – 12 weeks | 25,700 – 288,000 |
| 13 – 16 weeks | 13,300 – 254,000 |
| 17 – 24 weeks | 4,060 – 165,400 |
| 25 – 40 weeks | 3,640 – 117,000 |
Notice how wide every range is, and how much neighboring weeks overlap: at 5 weeks the top of the range (7,340) already exceeds the bottom of the 7–8 week range, and a healthy 4-week value of 400 would look low at 6 weeks. That overlap is why a single value is nearly useless alone, and why the change between two values — what this calculator measures — matters more than either value by itself.
| Output | Formula | What it means |
|---|---|---|
| 48-hour rise | (second ÷ first − 1) × 100 | +120% at the defaults — the level more than doubled in 48 hours. |
| Doubling time | hours × ln(2) ÷ ln(second ÷ first) | 42.2 hours at the defaults — how long the level would take to double at this pace. |
| Band | rise vs ~53% in 48 h; doubling vs ~60 h | Expected range at the defaults; slower rise or fall means follow up with your clinician. |
The arithmetic is exact for the numbers entered, but the numbers themselves carry error: different labs and assays can report different values for the same sample, blood-draw timing is rarely exactly 48 hours, and hCG naturally rises more slowly as pregnancy advances — after about 6–7 weeks the doubling time lengthens and the 48-hour rules on this page stop applying well. Very high values, multiple pregnancies, fertility medications containing hCG, and recent pregnancy loss all distort the picture. This page cannot see any of that, which is why it is educational only. Error policy: zero or negative hCG values, a second value of zero or less, and zero or negative hours are reported as errors rather than modeled.
Bright Side Kit. "hCG Doubling Time Calculator: Early Pregnancy Rise Check." https://brightoolbox.com/hcg-doubling-calculator/ Accessed October 24, 2026.Data sourcesIn very early pregnancy, roughly every 48 hours is the textbook pace, and a rise of about 53% or more in 48 hours is commonly expected. At the defaults here, 500 to 1,100 in 48 hours gives a 42.2-hour doubling time. Doubling slows as pregnancy advances, so these rules fit the earliest weeks best.
Doubling time = hours × ln(2) ÷ ln(second ÷ first). For 500 to 1,100 in 48 hours: 48 × 0.6931 ÷ ln(2.20) = 42.2 hours. The 48-hour rise is simpler: (1,100 ÷ 500 − 1) × 100 = +120%.
No. A slow rise can mean the pregnancy is earlier than dated, a miscarriage, or an ectopic pregnancy — blood values alone cannot distinguish them. A slow pair is a reason for repeat testing and ultrasound follow-up with your clinician, not a diagnosis from a calculator.
Usually a sustained fall means the pregnancy is ending, but only your clinician can confirm that with repeat tests and, when needed, ultrasound. Never assume a single falling pair is final, and never delay calling your clinician about it.
No. Home tests show lines, not numbers, and line darkness does not track hCG reliably — it varies with urine concentration, test brand, and lighting. Doubling time needs two quantitative blood (beta hCG) results.
Because assays differ. Different laboratories use different test methods and calibrations, so the same sample can read differently. Use results from the same lab for a doubling calculation whenever possible, and compare each result to its own lab's reference range.
Commonly published ranges put 5 weeks at roughly 18 to 7,340 mIU/mL — an enormous span. Ranges vary by lab and assay, dating can be off by a week, and twins raise hCG. A single value in or out of the range proves nothing alone; the change between values matters more.
Call promptly for any slow rise or fall, and seek urgent care for bleeding, severe abdominal pain, dizziness, or shoulder-tip pain. Those symptoms can accompany an ectopic pregnancy, which needs emergency evaluation. This page is educational only and never a substitute for that call.