# hCG Levels Calculator (Doubling Time)

URL: https://speedycalculator.com/calculators/health/hcg-levels/
Last updated: 2026-10-30

> The hCG calculator works out how quickly the pregnancy hormone hCG is rising between two blood tests – the doubling time and the percentage increase over 48 hours – and compares it with the expected rise in early pregnancy.

## Inputs

- First hCG (mIU/mL)
- Second hCG (mIU/mL)
- Hours between tests (h)

## Results

- Doubling time
- Rise over 48 hours
- Interpretation

## Formula

```
Doubling time (h) = t × ln 2 ÷ ln(hCG₂ ÷ hCG₁)
48-hour rise (%) = ((hCG₂ ÷ hCG₁)^(48 ÷ t) − 1) × 100
```

## Explanation

In a healthy early pregnancy, hCG typically doubles every 48–72 hours until about 6–7 weeks. A rise of at least 35–50% in 48 hours is expected in most viable intrauterine pregnancies; slower rises or falls need follow-up to rule out miscarriage or ectopic pregnancy.

### How to use the hCG Levels Calculator

- **First hCG**
- **Second hCG**
- **Hours between tests**

Results update as you type, and every field accepts the units shown in its menu.

### How it works

Enter the two hCG results and the number of hours between the blood tests.

### Inputs explained

FieldWhat to enterFirst hCGIn mIU/mLSecond hCGIn mIU/mLHours between testsIn h

### Example values

How the main result changes when **First hCG** changes and everything else stays at the example values above:

First hCG (mIU/mL)Doubling time (hours)60239031120431506018090240416
*Health note: this calculator is for education and screening only and is not a diagnosis or treatment advice. Discuss your results with a qualified clinician.*

## Worked example

Inputs — First hCG: 120 mIU/mL; Second hCG: 260 mIU/mL; Hours between tests: 48 h.

Results — **Doubling time = 43 hours**; Rise over 48 hours = 117 %; Interpretation = Rise consistent with a progressing early pregnancy.

## Key terms

- **hCG**: Human chorionic gonadotropin.

## FAQ

**How fast should hCG rise?**
Usually doubling every 48–72 hours in the first weeks.

**Does hCG keep doubling?**
No – the rise slows after about 6–7 weeks and peaks at 8–11 weeks.

**Can one hCG value tell me if the pregnancy is OK?**
Not on its own; the trend and an ultrasound are needed.


## Sources

- [Barnhart KT et al. Symptomatic patients with an early viable intrauterine pregnancy: hCG curves redefined. Obstet Gynecol, 2004](https://pubmed.ncbi.nlm.nih.gov/15229000/)