Pregnancy Weeks Calculator
This pregnancy weeks calculator tells you exactly how far along you are. Choose whether to count from the first day of your last menstrual period (LMP) or from your conception date, enter that date, and it instantly returns your gestational age in completed weeks and days, which trimester you are in, your estimated due date, how many days are left, and the percentage of the pregnancy already completed. If you would rather focus on the delivery date or on your fertile window, see the companion due date calculator and ovulation calculator.
Weeks pregnant
Trimester
Days remaining
Estimated due date
Pregnancy progress
A guiding estimate based on Naegele’s rule and a regular cycle; it does not replace your obstetrician’s care. An early ultrasound gives more precise dating.
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How it works
When counting from the last menstrual period, gestational age is simply the number of days between your LMP and today, expressed in weeks and days; if your cycle is longer or shorter than 28 days, the start is shifted by the difference (cycle − 28) because ovulation happens correspondingly later or earlier. The due date is your LMP plus 280 days (Naegele’s rule), also adjusted for cycle length. When counting from conception instead, two weeks are added, because conventional pregnancy dating begins about 14 days before conception; the due date is then conception plus 266 days. Trimesters are split by gestational week: first through week 13, second from weeks 14 to 27, and third from week 28 onward. Progress is measured against the full 280-day span.
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Preguntas frecuentes
- How many weeks pregnant am I?
- Your weeks pregnant equal your gestational age: the number of completed weeks and days since the first day of your last menstrual period. If you know your conception date instead, the calculator adds about two weeks, because pregnancy is conventionally dated from the LMP, roughly 14 days before conception.
- Should I count from my last period or from conception?
- Counting from the last menstrual period (LMP) is the medical standard and usually the easiest date to remember. Count from conception only if you are confident about the date (for example after a known ovulation or IVF transfer). Both options give the same style of result; they differ by about two weeks in how the start is defined.
- How are the three trimesters divided?
- By gestational week: the first trimester runs through week 13, the second from weeks 14 to 27, and the third from week 28 until birth. The calculator shows which trimester your current gestational age falls into.
- Why does cycle length matter?
- The standard calculation assumes a 28-day cycle with ovulation on day 14. A longer cycle means you ovulate and conceive later, so your weeks pregnant are slightly fewer and your due date is later; a shorter cycle shifts it the other way. Cycle length only applies when counting from the last menstrual period.
- How accurate is this estimate?
- It is a good guide when your cycles are regular, but only about 1 in 20 babies arrive exactly on the estimated due date. An early ultrasound gives the most precise dating and is what clinicians rely on. See our due date and ovulation calculators for related estimates, and always follow your obstetrician’s assessment.