Pregnancy Due Date Calculator

The estimated due date (EDD) is calculated by adding 280 days (40 weeks) to the first day of your last menstrual period (LMP). This is known as Nägele's rule: add 7 days to the LMP date, then add 9 calendar months (or subtract 3 months and add 1 year). The method assumes a 28-day cycle with ovulation on day 14.

If you know the conception date, the calculator adds 266 days (38 weeks) instead. For cycles longer or shorter than 28 days, the due date is adjusted accordingly — for example, a 35-day cycle shifts the EDD forward by 7 days.

The NHS offers all pregnant women a dating scan between 8 and 14 weeks, which measures the baby's crown-rump length to refine the due date. Only about 4% of babies arrive on their exact due date; most are born within two weeks either side. The NHS considers pregnancies overdue at 42 weeks.

How is the due date calculated? Naegele's Rule: LMP (Last Menstrual Period) + 280 days = estimated due date. Or: LMP date + 1 year − 3 months + 7 days. Sample: LMP 1 May = due date 5 February next year. Assumes 28-day cycle and ovulation on day 14. Longer cycles: add the extra days. Shorter cycles: subtract. Only 4% of babies are born exactly on due date. 80% born within 2 weeks either side. NHS dating ultrasound (8-14 weeks) is more accurate than LMP — adjusts due date if 7+ days difference.

NHS antenatal appointment schedule. Week 8-12: booking appointment, full medical history, blood tests. Week 11-14: dating scan + Down's screening. Week 18-21: anomaly scan. Week 25 (first pregnancy): midwife check. Week 28: blood tests, anti-D if Rh negative. Week 31, 34, 36 (first pregnancy): midwife appointments. Week 38, 40, 41: midwife checks. Week 41+: induction discussion. NHS Maternity Pay starts 11 weeks before due date (29 weeks pregnant) earliest.

UK Maternity Allowance and Pay 2026/27. Statutory Maternity Pay (SMP): first 6 weeks at 90% of weekly earnings; remaining 33 weeks at £187.18/week or 90% of earnings (whichever lower). Total 39 weeks paid + 13 weeks unpaid = 52 weeks. Maternity Allowance for self-employed/not eligible for SMP: £187.18/week for 39 weeks. Eligibility: continuous work for same employer for 26 weeks ending 15 weeks before due date. Notice: tell employer at least 15 weeks before due date.

Pregnancy trimesters and key milestones. First trimester (weeks 1-12): nausea, fatigue, breast tenderness; highest miscarriage risk (10-25% of confirmed pregnancies). Second trimester (13-27): often most comfortable; baby movements felt 16-22 weeks; anomaly scan 18-21 weeks. Third trimester (28-40+): increasing discomfort; baby reaches viability 24 weeks (legal abortion limit UK); 'term' from 37 weeks; 'overdue' from 42 weeks (induction discussed at 41).

Folic acid and pregnancy supplements. NHS recommends 400mcg folic acid daily from 3 months before conception until week 12. Reduces neural tube defects (spina bifida) by 70%. Higher dose 5mg for: diabetes, BMI 30+, family history of NTD, taking anticonvulsants — prescription. Vitamin D 10mcg daily entire pregnancy and breastfeeding (NHS recommendation since 2016). Avoid: liver, vitamin A supplements (teratogenic in high doses), unpasteurised dairy, undercooked meat, alcohol, smoking. Caffeine: NHS limit 200mg/day (2 mugs of coffee).