Enter the first day of your last period to find out how far along you are today, which trimester you are in, your estimated due date, and days remaining.
Estimates only.
Gestational age is counted from the first day of your last menstrual period (LMP), not from conception. This is the standard used by obstetricians worldwide because LMP is a known date, while the exact moment of conception is usually unknown. Under this system, a full-term pregnancy is 40 weeks (280 days) from LMP.
Gestational age is distinct from fetal age (time since conception), which is typically about 2 weeks less. The results shown here are general estimates based on a 28-day cycle starting from LMP. They are not medical advice. An early ultrasound (dating scan) is the clinical standard for confirming gestational age and is more accurate than LMP alone, especially if your cycles are irregular. Always confirm your due date and pregnancy progress with your doctor or midwife.
Gestational age is calculated from the first day of the last menstrual period (LMP). Count the number of days from LMP to today, then convert to weeks and days. For example, 70 days from LMP equals 10 weeks exactly. This calculator does that automatically based on today's date.
Subtract your LMP date from today's date to get the total number of days, then divide by 7. The whole number is weeks; the remainder is extra days. So 85 days from LMP is 12 weeks and 1 day (12w 1d). This is the same method used in clinical practice.
Both are used. LMP-based dating is the standard starting point. An early ultrasound (ideally between 8 and 13 weeks) can refine the estimate by measuring the fetal crown-rump length. If the ultrasound date differs significantly from the LMP date, providers typically adjust the due date to the ultrasound measurement. LMP-only estimates can be less accurate when cycles are irregular.
In early pregnancy, sonographers measure the crown-rump length (CRL) of the fetus. This measurement corresponds to published growth tables that translate the size into a gestational age estimate. CRL is most accurate between 6 and 13 weeks. After 13 weeks, head circumference, femur length, and abdominal circumference are used instead. An ultrasound dating scan is more precise than LMP alone.