Working from a positive test
Home pregnancy tests detect hCG, which rises after the embryo implants. For most people, a test turns positive around the time a period is missed — about 4 weeks of pregnancy, counted in the usual way from the last period. That makes the date of your first positive test a useful clue when you don’t know when your last period started.
Tell the calculator when you got your first positive and whether you tested before your period was due, on the day it was due, or after it was late. It estimates how far along you were on the test day, the likely start of your last period, and a range of due dates with a best guess in the middle.
How far along at the first positive?
| When you tested | Likely gestational age |
|---|---|
| Before your period was due (early test) | About 3w3d – 4w0d |
| The day your period was due | About 3w6d – 4w2d |
| After a late period | About 4 weeks + the number of days late (± a few days) |
Why it’s only an estimate
A positive test tells you hCG has reached the test’s threshold, which depends on when implantation happened (6–12 days after ovulation), how quickly hCG rises, the test’s sensitivity and how concentrated your urine was. And many people don’t test on the first possible day. So treat the result as a starting point.
Next steps
- Contact a doctor or midwife to book your first appointment.
- If you have any idea of your last period’s month, the Pregnancy Estimator can narrow the range.
- Your dating scan will give an accurate due date — then use the Ultrasound Due Date Calculator.
Seek medical advice promptly if you have pain on one side, bleeding, shoulder-tip pain or feel faint.