How Many Weeks Pregnant Am I? Week-by-Week Calculator

Free weeks pregnant calculator: see how many weeks and days pregnant you are today, your trimester, due date and days to go, plus a week-by-week table with start dates and baby size. From your last period, conception, IVF or ultrasound. Private.

🔒 Private by design: your dates are saved only in this browser (never uploaded, no account) and are shared by the three calculators below.

Day 1 of one period to day 1 of the next. 28 is the textbook average; most people are 24–35.
More options: period length, luteal phase, ovulation (LH) test
Ovulation to next period. 14 is typical (11–16 is normal).
Optional: from a temperature chart or an ultrasound. Replaces the estimate.
Optional. Ovulation usually follows 24–36 hours later, so this sharpens the estimate.

A longer or shorter cycle moves ovulation, so the due date shifts with it.

These are estimates from averages, not medical advice or contraception. Bodies vary and cycles change with stress, illness, breastfeeding and age. Talk to a doctor or midwife about your own situation, especially if your cycles are very irregular or you have been trying for 12 months (6 if you are over 35).

How many weeks pregnant am I?

Enter the first day of your last period (or your conception date, an IVF transfer, a scan, or your due date) and see exactly how many weeks and days pregnant you are today, your trimester, how long is left, and a week-by-week list with the start date of every week and the size your baby is compared with a fruit or vegetable.

Good to know

  • Weeks are counted from the first day of your last period, not from conception. A full pregnancy is 40 weeks.
  • Trimesters: first to the end of week 13, second weeks 14–27, third from week 28.
  • Term: 37 to 38+6 weeks is early term, 39 to 40+6 full term, 41 to 41+6 late term, and 42 weeks or more post-term.
  • The size comparisons and measurements are typical averages, and healthy babies vary.

Questions

How many months is 20 weeks?

Pregnancy is about 9 months, and a month is 4.3 weeks, so 20 weeks is a little under 5 months. Doctors prefer weeks because months are different lengths.

Can I be 6 weeks pregnant when I only conceived 4 weeks ago?

Yes. Because weeks are counted from your last period, which comes about two weeks before conception, you are always about two weeks “ahead” of the real age of the embryo.

Also see the due date calculator with key dates, and the conception date calculator.

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