📅 Pregnancy Due Date Calculator
Enter your LMP date to find your baby's due date and current pregnancy week
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How is the due date calculated?
Your due date is estimated by adding 280 days (40 weeks) to the first day of your last menstrual period (LMP). This is known as Naegele's rule and is the most common method used by doctors worldwide.
This calculator provides an estimate only. Please consult your doctor or gynecologist for accurate medical advice and confirmation of your pregnancy timeline.
How to use this tool
Uses Naegele's Rule. The standard medical formula worldwide. Takes 30 seconds.
- 1Enter your Last Menstrual Period (LMP) date
The first day your last period started. Not when it ended. Check your period app if unsure.
- 2Enter your average cycle length
Default is 28 days. Update if your cycle is shorter or longer for a more accurate result.
- 3Click Calculate Due Date
Your due date, current week, trimester, and countdown appear instantly.
- 4Save or screenshot your results
Take a screenshot to share with your doctor. Return anytime to check your current week.
Your first ultrasound can shift the due date by a few days. This is normal. Ultrasound dating is more accurate if they differ by more than 5 days.
Your due date is an estimate. Babies born between 37 and 42 weeks are full-term. Do not stress if your date changes slightly.
Frequently Asked Questions
How accurate is this calculator?
What if I do not know my LMP date?
My cycle is not 28 days. Does this matter?
Can I use this for IVF?
How pregnancy due date estimation care actually works in the United Kingdom
UK pediatric care runs through the NHS. Generally well organised. Can feel slow at peak times. Your first call is usually NHS 111. Free, 24/7. They triage what is going on and tell you what level of care to seek. Sometimes a GP appointment via e-Consult. Sometimes A and E. Occasionally an ambulance. Out of hours GP services run evenings and weekends. Walk in centres and Urgent Treatment Centres handle the mid range stuff. A and E is for genuine emergencies, not routine fever queries, where you can wait many hours. For babies under 3 months though, A and E is the right call regardless. The NHS Pharmacy First service can also handle minor childhood things now without a GP appointment.
In the UK, call NHS 111 for non-emergency advice 24/7. For emergencies, call 999. Many GP practices have an after hours triage line. Your Health Visitor is also a valuable resource for baby questions during weekday hours. Pharmacies like Boots offer free advice from pharmacists for non-emergency concerns through the Pharmacy First service.
What British mums actually deal with
British mums often feel pressure to wait it out before bothering the NHS. This is wrong thinking. NHS 111 was designed for exactly these calls. Staff are trained to triage and there is genuinely no judgment for calling. Health Visitors are an underused resource. They expect to hear about concerns in young babies. They can advise on what is normal during teething (mild temperature elevation, yes). True fever above 38 Celsius is something else and worth a proper assessment. British medical practice runs more conservative on medication than American practice. Calpol is the workhorse. Talk to your GP or pharmacist before alternating with Nurofen, NICE specifically does not recommend routine alternating.