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hCG Calculator

Enter two quantitative (beta) hCG blood results with the date and time of each, and this calculator shows your doubling time, the percent change, and the projected 48-hour rise — so you can see how your levels are trending in early pregnancy.

First test
Second test

Enter both quantitative (beta) hCG blood results with the date and time of each draw to see the doubling time and rate of rise.

What is hCG?

hCG — human chorionic gonadotropin — is the hormone the developing placenta produces in pregnancy. It’s what a pregnancy test looks for. A quantitative (beta) hCG blood test goes a step further than a home test: instead of a yes/no, it measures the exact amount of hCG in your blood in mIU/mL. Because hCG climbs predictably in the first weeks, providers often order two beta tests a couple of days apart and look at how the number changes, rather than reading a single value on its own.

What “doubling time” means

In early pregnancy, hCG rises quickly — as a rule of thumb it roughly doubles every 48 to 72 hours while levels are still low. A widely used clinical benchmark is that hCG should climb by at least about 35% over 48 hours. The doubling time is simply how long, at the rate measured between your two tests, it would take the level to double.

One important nuance: the doubling slows as pregnancy progresses. Once hCG is in the thousands or you’re past about 6–7 weeks, it rises more slowly and takes longer to double, and that slow-down is expected. So a longer doubling time at a higher level is not the same as a slow rise at a low level.

How to use this calculator

  • Enter your first beta hCG result and the date and time of that blood draw.
  • Enter your second result and its date and time (it should be later than the first).
  • You’ll see the doubling time, the percent change between the two values, and the projected 48-hour rise, with a plain-language note on how that pattern is generally read.

For the typical ranges at each stage, see our hCG levels by week chart.

What the result can — and can’t — tell you

This tool describes a pattern: it tells you how fast your numbers are moving. What it can’t do is diagnose why they’re moving that way. A reassuring rise is encouraging but isn’t a guarantee, and a slow or falling pattern has several possible explanations — from a normal higher-level slow-down to an ectopic pregnancy or an early loss — that only your provider can sort out, usually with repeat tests and an ultrasound.

Please treat the result as a way to understand your own numbers between appointments, not as a verdict. If anything looks off, or you have pain or bleeding, contact your provider. If you have sudden, severe tummy pain or shoulder-tip pain, or feel very dizzy or faint, call 999 (UK) or 911 (US) straight away.

Frequently asked questions

How fast should hCG rise in early pregnancy?
In early pregnancy, hCG typically rises by at least about 35% over 48 hours, and often roughly doubles every 48–72 hours while levels are still low. As levels climb higher (and past about 6–7 weeks), the rise naturally slows down, so a longer doubling time at higher levels can be completely normal. These are general patterns, not a diagnosis — your provider interprets your numbers in context.
How is hCG doubling time calculated?
Doubling time is worked out from how much your hCG rose between two blood tests and how many hours apart they were. The formula uses the growth rate between the two values: doubling time = hours between tests × ln(2) ÷ ln(second value ÷ first value). This calculator does that for you and also projects the rise out to 48 hours so it's easy to compare against the usual early-pregnancy pattern.
What does a slow-rising hCG mean?
A slower-than-expected rise can have several explanations — it can simply reflect higher starting levels or a slightly later stage, a pregnancy that's still establishing, an ectopic (tubal) pregnancy, or an early loss. A single pair of numbers can't tell which, which is why this is something to review with your provider, usually alongside repeat tests and an ultrasound. The calculator describes the pattern; it does not diagnose the cause.
Can I tell how many weeks pregnant I am from one hCG level?
Not reliably. The typical range for any given week is extremely wide and overlaps heavily with neighbouring weeks, so a single hCG value rarely pins down how far along you are. The trend across two or more tests is far more informative than one number, and an early ultrasound is the most accurate way to date a pregnancy. See our hCG levels by week page for the typical ranges.
Is a quantitative hCG the same as a home pregnancy test?
No. A home urine test is qualitative — it gives a yes/no answer once hCG passes a threshold. The numbers this calculator uses come from a quantitative (beta) hCG blood test, which measures the exact amount in mIU/mL. You need two of those blood results, taken a couple of days apart, to look at the rate of rise.

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— The Period Tools Team

Sources

Checked against the following public guidance on September 26, 2026. Advice can differ between countries; your doctor, nurse or midwife can apply it to you.

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