Pregnancy due date
An estimated due date, current gestational age and trimester, worked out from the first day of your last period.
Choose the first day of your last period to see an estimate.
How the date is calculated
This uses Naegele's rule: 280 days from the first day of your last menstrual period. Because that rule assumes a 28-day cycle with ovulation on day 14, the calculator adjusts if your cycles are longer or shorter.
Only about 4 in 100 babies arrive on the date
A due date is the midpoint of a range, not an appointment. Most births happen between 37 and 42 weeks, and arriving a week or two either side of the estimate is entirely normal.
A dating scan beats this calculator
An ultrasound in the first trimester measures the baby directly and is considerably more accurate than any date-based estimate — particularly if your cycles are irregular, you were recently on hormonal contraception, or you are unsure of the date of your last period. If a scan has given you a different due date, use the scan's.
Please get proper antenatal care
A calculator is no substitute for antenatal care. Contact your doctor or midwife straight away if you have bleeding, severe or persistent abdominal pain, a bad headache with visual changes, sudden swelling of the face or hands, fever, fluid leaking, or reduced movements later in pregnancy.