Question 1

How accurate is a due date calculator?

Accepted Answer

A due date is an estimate, not a deadline. Only about 1 in 20 babies are born on their exact due date, and most arrive within a week or two either side. Calculations from your last period assume a 28-day cycle with ovulation on day 14; an early ultrasound scan (before 13 weeks) is generally the most accurate way to date a pregnancy.

Question 2

Why do doctors count pregnancy from my last period, not conception?

Accepted Answer

Because the first day of your last period is a date most women know, while the exact moment of conception usually isn't. Pregnancy is counted as 40 weeks from that day — even though conception typically happens about two weeks later, around ovulation.

Question 3

What if my cycles are irregular?

Accepted Answer

If your cycles are longer, shorter or irregular, a last-period calculation can be off by days or even weeks. Enter your average cycle length to improve the estimate, and rely on your first ultrasound scan for the most reliable date.

Question 4

Is my data private?

Accepted Answer

Yes. These calculators run entirely in your web browser. The dates you enter are never sent to a server, stored, or shared — close the tab and they are gone.

Question 5

When should I see a doctor after a positive test?

Accepted Answer

Contact your doctor, midwife or local maternity service once you have a positive pregnancy test — most first appointments happen between 8 and 12 weeks. Seek medical advice sooner if you have pain, bleeding, a history of ectopic pregnancy, or a long-term health condition.

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