Pregnancy Week Calculator
How far along you are, week by week.
| How far along | 0 weeks 0 days |
| Trimester | First trimester |
| Calendar month of pregnancy | 3rd month |
| Estimated due date | 2027-07-18 |
| Days remaining | 280 days (40 weeks) |
| Progress | 0% of the way to 40 weeks |
| Second trimester starts | 2027-01-10 |
| Third trimester starts | 2027-04-18 |
Results update instantly and are computed entirely in your browser. For general information only — not medical, financial or professional advice.
About the pregnancy week calculator
Pregnancy is dated from the first day of your last menstrual period, not from conception. That convention surprises almost everyone at first: because ovulation happens roughly two weeks after the period begins, you are counted as "two weeks pregnant" at the moment of conception. When a midwife says you are twelve weeks along, they mean twelve weeks of gestational age.
To work out how far along you are, take the number of days between the first day of your last period and today, then divide by seven. The remainder gives you the days. So 87 days is twelve weeks and three days. If your cycle is regularly longer or shorter than 28 days, ovulation — and therefore the whole timeline — shifts by the same amount, which is why this calculator asks for your cycle length and adjusts the due date accordingly.
The trimesters divide the forty weeks into three roughly equal parts. The first trimester runs to the end of week 12, the second to the end of week 27, and the third from week 28 until birth. Development is front-loaded: by the end of the first trimester every major organ is already formed, and the remaining months are mostly about growth, maturation and the lungs preparing for air. That is also why the first trimester is the one where most caution is advised, and why early scans are the most useful for dating.
Keep two things in mind. Only about four per cent of babies are born on the due date, so treat these numbers as a window rather than a deadline. And a dating ultrasound in the first trimester is more accurate than any calculation from your period, so once you have had one, use the scan date and let the calculator follow it rather than the other way round. This tool is general information, not medical advice — your midwife or doctor is the person to ask about your own dates.
This calculator returns estimates for general information only. It is not medical advice, diagnosis or treatment, and it cannot replace an assessment by a qualified health professional. Individual results vary, and figures such as calorie needs, body-fat percentage and heart-rate zones are approximations based on population averages rather than measurements of you.