Due Date Calculator & UK Pregnancy Tracker
Calculate Your Due Date
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How Is Your Due Date Calculated?
Understanding how your estimated due date (EDD) is determined helps you plan ahead with confidence. Here are the four primary methods and insights.
Last Menstrual Period (LMP)
Most pregnancy due dates are calculated based on the first day of your last menstrual period. Since the exact date of conception is rarely known, this provides a standardized starting point.
Pregnancy is traditionally measured as 40 weeks (280 days) starting from this date.
Calculate your due date →Conception Date
If you track your ovulation or know the exact date of conception (common with IVF or assisted reproductive techniques), your due date can be calculated by adding 266 days directly to that date.
This method is highly precise when conception timing is certain.
Try the conception date method →NHS Dating Scans
Between 11 and 14 weeks of pregnancy, the NHS offers a dating scan. The sonographer measures your baby from head to bottom (crown-rump length) to estimate gestational age.
Ultrasound measurements at this stage are considered the most accurate way to establish your due date.
Learn about Week 12 →Due Dates Are Estimates
It is completely normal if your baby does not arrive exactly on their due date. In fact, only about 5% of babies are born on their estimated date.
The vast majority of babies arrive within a range of 2 weeks before to 2 weeks after their estimated due date.
Track your pregnancy timeline →Track Your Pregnancy Week by Week
Follow your baby's rapid development and monitor key milestones tailored to the UK healthcare timeline.
Weekly Development Updates
Track how your baby grows from a tiny seed to a full-term newborn, with detailed weekly updates and symptom trackers designed to support your body.
Explore Week by Week →Due Date Tracker & Countdown
Stay updated with an interactive countdown clock, visual trimester indicators, and tailored milestones tracking from week 1 through week 40.
Track Your Pregnancy →NHS-Aligned Guidance
Access a curated list of trusted UK resources, benefit details, legal rights at work, and professional clinical guidelines from the NHS and NICE.
Pregnancy Resources →Pregnancy Blog
Read clinical advice, budget tips, and features written for expectant parents in the UK.
Read Articles →UK Pregnancy Guidance Based on NHS Milestones
A roadmap of standard NHS midwife check-ups and screening scans during your pregnancy journey in the UK.
Midwife Booking Appointment
Your first official appointment with a midwife. They will discuss your general health, history, calculate your initial estimated due date, and arrange your screening tests and upcoming scan appointments.
Read about Week 8 →12-Week Dating Scan
This ultrasound scan officially estimates your due date by measuring the crown-rump length of the baby. The sonographer will also check your baby's physical development and offer screening tests for genetic conditions if desired.
Read about Week 12 →20-Week Anomaly Scan
A detailed ultrasound scan that looks closely at your baby's bones, heart, brain, spinal cord, and other major organs. This scan checks that your baby is growing well and is also the moment you can typically find out the biological sex of your baby.
Read about Week 20 →28-Week Antenatal Appointment
Midwife check-up to measure your bump size, check blood pressure, test your urine for protein, and discuss the baby's active movements. Anti-D treatment may be offered at this stage if your blood type is rhesus negative.
Read about Week 28 →36-Week Final Prep Appointment
Your midwife will check the baby's position (ideally head down). They will also discuss your birth preferences, signs of labour, pain relief options, and emergency contacts to prepare for your baby's arrival.
Read about Week 36 →Why DueDate.Baby?
Navigating pregnancy can be overwhelming. We cut through the noise to provide clear, relevant information specifically for parents navigating the UK healthcare system.
NHS-Aligned Information
Our content follows current NHS guidelines and recommendations.
UK-Specific Advice
From Statutory Maternity Pay to booking your midwife, it's all relevant to you.
Actionable Checklists
Simple, tickable timelines and guides that make preparation stress-free.
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Pregnancy Due Date & Calculator FAQs
Clear, medically accurate answers to common questions about estimating and tracking your due date in the UK.
How accurate is a due date calculator?
A standard due date calculator estimates your delivery date using your Last Menstrual Period (LMP) as a baseline. While it provides an excellent early reference point, only about 5% of babies arrive precisely on their due date.
For the highest level of accuracy, an NHS dating ultrasound scan performed between 11 and 14 weeks measures the baby’s physical size (crown-rump length) and confirms or adjusts your official due date.
How is my due date calculated?
A typical human pregnancy lasts approximately 40 weeks (280 days) from the first day of your last menstrual period. Under Naegele's Rule, which calculators use, your due date is calculated by adding 280 days to the first day of your LMP, assuming a regular 28-day menstrual cycle.
If your menstrual cycle is longer or shorter than 28 days, a digital calculator adjusts this baseline to account for the difference in ovulation timing.
Can my due date change during pregnancy?
Yes, it is very common for your due date to change slightly. The calendar estimate based on your last period assumes immediate ovulation and perfect matching.
When you have your 12-week dating scan, the ultrasound measurements give a much more accurate picture of the baby's development rate. If this measurement differs from the period-based timeline by more than a few days, your midwife will officially update your due date.
What if I don't know my conception date?
You do not need to know your exact conception date! Most expectant parents do not. In fact, calculating from the first day of your Last Menstrual Period (LMP) is the standard method used by clinical practices.
Your NHS booking appointment and dating scan are scheduled specifically to resolve any timeline uncertainties, ensuring your prenatal care matches your actual gestational weeks.
How many weeks pregnant am I?
Your pregnancy is counted in completed weeks and days starting from the first day of your last menstrual period. For example, if your last period began 5 weeks and 3 days ago, you are in your 6th week of pregnancy (referred to as "5 weeks pregnant").
You can use our online Due Date Calculator or pregnancy tracker to input your cycle details and immediately see your exact current week, trimester, and countdown.
When will I have my NHS dating scan?
The standard NHS dating scan is scheduled between week 11 and week 14 of your pregnancy. This scan is completely free under the NHS, and your midwife will help coordinate the referral at your booking appointment (which typically happens around week 8 to 10).
Do all babies arrive on their due date?
No, it is extremely rare for a baby to be born exactly on their due date (only about 5% of cases). Most healthy babies are born within a broader window between 37 and 42 weeks of pregnancy.
Babies born before 37 weeks are considered pre-term, and babies born after 42 weeks are considered post-term. Midwives and doctors will discuss options with you, including potential induction of labour, if your pregnancy extends beyond 41 weeks.