Gestational Age Calculator
How many weeks pregnant am I? Start with the due date in your pregnancy record, the first day of your last period, or pregnancy weeks already written on a dating scan or dated record. See your gestational age in completed weeks and additional days for today or another date.
This tool calculates calendar timing only. It does not assess pregnancy health, fetal growth, wellbeing, or viability.
Free browser-based pregnancy and preconception calculators with transparent methods, sources, assumptions, and limitations.
How to use this gestational age calculator
- Choose the current recorded due date when your care team has already established one.
- Use the first day of your last period only when it is reliable and a different clinical due date has not replaced it.
- Or enter completed weeks, additional days, and the date already written on the same dating scan or pregnancy record.
- Use today, or choose another date that you want to check.
Need to estimate a due date first? Use the Pregnancy Due Date Calculator. For IVF or embryo-transfer dating, use the IVF Due Date Calculator.
What does gestational age mean?
Gestational age is pregnancy calendar time written as completed weeks plus additional days. 8w4d means 8 completed weeks and 4 additional days—not 8.4 decimal weeks.
Pregnancy weeks usually begin from the last-period-based obstetric calendar. They are not the same as an exact fetal or conception age, because fertilization happens later and its exact timing is often not known.
When your pregnancy record already has an established estimated due date (EDD), use that recorded EDD as the anchor. This calculator does not interpret ultrasound measurements, assess viability, fetal growth or wellbeing, or clinically redate a pregnancy.
This page calculates gestational age during pregnancy before delivery. It is not a corrected-age, adjusted-age, or postmenstrual-age calculator for a premature baby after birth.
How pregnancy weeks, due dates, and dating records fit together
For the deeper explanation of completed weeks and days, pregnancy-calendar starts, due-date methods, clinical dating differences, and how each result is derived, read the Pregnancy Dating Explained: Due Dates, Weeks & Conception.
Frequently asked questions
- How do I calculate how many weeks pregnant I am?
- Choose the due date currently recorded for your pregnancy when you have one. Otherwise, use a reliable first day of your last period or completed pregnancy weeks and days already written on a dated record. The calculator shows completed weeks and additional days for today by default.
- Can I calculate gestational age from my due date?
- Yes. The calculator subtracts 280 days from the recorded due date to establish the pregnancy-calendar start, then counts forward to the date you want to check. Use the current due date in your pregnancy record rather than averaging older dates.
- Can I calculate gestational age from my last period?
- Yes, when the first day of your last period is reliable and a different clinical due date has not already been established. This path counts elapsed calendar days directly from that date; it does not add a cycle-length adjustment.
- Can I use pregnancy weeks from a dating scan or dated record?
- Yes. Enter the completed weeks, additional days, and date already written on the same record. The calculator does not accept or interpret ultrasound measurements and does not decide whether the pregnancy should be clinically redated.
- What does 8 weeks, 4 days pregnant mean?
- It means 8 full weeks have been completed and 4 additional days have passed. The compact notation is 8w4d; it does not mean 8.4 decimal weeks.
- Can I check how many weeks pregnant I will be on another date?
- Yes. Choose Check another date and enter a date within the supported pregnancy-calendar range. This changes only the date checked, not the pregnancy record or due date used as the anchor.
- Why is my clinic or ultrasound pregnancy age different?
- Last-period dates can be uncertain, and clinical dating may use ultrasound findings or treatment records. Use the current due date and pregnancy age established in your record; this calculator cannot decide whether either should change.
- Is gestational age the same as fetal age?
- No. Gestational age follows the pregnancy-dating calendar, which usually starts from the last-period-based reference. Fetal or conceptional age starts closer to fertilization, and an exact biological age cannot be established from calendar dates alone.