Due Date Calculator
When is your baby due? Enter the first day of your last period, your conception date, an ultrasound result or your IVF transfer date to find your estimated due date, how many weeks pregnant you are, and the key dates ahead.
0% of pregnancy complete
Your delivery window
| Category | Weeks | Dates |
|---|---|---|
| Early term | 37–38 | — |
| Full term | 39–40 | — |
| Late term | 41 | — |
| Post term | 42+ | — |
Only about 4% of babies arrive on their exact due date. Most are born within two weeks either side of it.
Key pregnancy dates
Healthy eating in pregnancy
- Breakfast: egg with whole wheat roti or paratha made with little oil, and a glass of milk
- Mid-morning: a banana or seasonal fruit with a small handful of almonds and walnuts
- Lunch: daal or chicken shorba with rice or roti, spinach (palak) or other sabzi, and salad
- Snack: a few dates (khajoor) with milk or unsweetened lassi
- Dinner: well-cooked fish or chicken, 1–2 roti and mixed vegetables
- Key nutrients: iron (daal, chana, spinach, lean meat), calcium (milk, yogurt, paneer), folic acid (green vegetables, plus the supplement your doctor recommends) and omega-3 (low-mercury fish, walnuts)
- Avoid: liver and liver products (too much vitamin A), undercooked meat or eggs, unpasteurised milk, and high-mercury fish such as shark and swordfish. Limit tea and coffee to about 2 cups a day.
General guidance only. Please follow your doctor's or midwife's advice, especially about supplements.
Getting ready for delivery
- Pack your hospital bag by week 36: ID card and medical file, newborn clothes, sanitary pads, a comfortable nightgown, snacks, phone charger and toiletries.
- Know the signs of labour: regular, strengthening contractions, your waters breaking, a "show" (mucus plug), and lower back pain that comes in waves.
- Register at your hospital in advance to avoid delays on the day.
- Talk to your doctor about your birth plan, including pain relief options and who will be with you.
- Stay active with gentle walking if your doctor agrees.
- Plan your transport to the hospital, including a backup option for night-time.
- Prepare newborn essentials: nappies, soft cotton clothes, swaddle blankets and feeding supplies.
- Arrange help at home for the first weeks after birth, so you can rest and recover.
Disclaimer: This due date is an estimate. Your doctor or midwife may adjust it after your dating ultrasound. Always follow their advice.
How is a due date calculated?
A typical pregnancy lasts about 40 weeks (280 days), counted from the first day of your last menstrual period (LMP), not from the day you conceived. This is because most people know when their period started, but not exactly when ovulation and conception happened. Conception usually takes place about two weeks after the start of your period, so by the time you conceive, you are already considered "two weeks pregnant".
Due date formulas used
From your last period (Naegele's rule): Due date = first day of LMP + 280 days. If your cycle is longer or shorter than 28 days, the calculator adjusts the date by the difference. For example, a 32-day cycle adds 4 days.
From conception: Due date = conception date + 266 days (38 weeks).
From an ultrasound: the pregnancy age measured on the scan is used to work backwards to your LMP, then 280 days are added. An early scan (before about 14 weeks) is the most accurate way to date a pregnancy.
From IVF transfer: Due date = transfer date + 266 days − embryo age. For a day 5 embryo, this is the transfer date + 261 days. IVF due dates are very precise because the exact age of the embryo is known.
Example: If the first day of your last period was 1 January 2026 and your cycle is 28 days, your estimated due date is 8 October 2026.
How accurate is my due date?
Your due date is an estimate, not a deadline. Only about 4% of babies are born on the exact day. Most arrive between 37 and 42 weeks, which is why doctors think of a "due month" rather than a due day. Irregular periods, uncertain period dates and differences in how long each pregnancy lasts can all shift the actual birth date. If your ultrasound date differs noticeably from your LMP date, your doctor will usually go by the ultrasound.
Pregnancy trimesters
| Trimester | Weeks | What happens |
|---|---|---|
| First | Weeks 1–13 | Baby's organs begin to form. Nausea and tiredness are common. |
| Second | Weeks 14–27 | Often the most comfortable stage. You may feel the baby move from about 16–22 weeks. |
| Third | Weeks 28–40 | Baby gains weight quickly and gets into position for birth. |
What does "term" mean?
Doctors describe births by the week they happen. Babies born between 37 and 38 weeks are early term, 39 to 40 weeks is full term, which has the best outcomes for most babies, 41 weeks is late term, and 42 weeks or more is post term. Babies born before 37 weeks are preterm and may need extra care. If pregnancy goes past 41 weeks, your doctor may talk to you about inducing labour.
When should I go to the hospital?
Contact your doctor or maternity unit if you have regular contractions (for example, every 5 minutes for an hour), your waters break, or you are unsure whether labour has started. Seek care immediately if you have heavy bleeding, severe headache or blurred vision, severe tummy pain, a high fever, or if your baby's movements slow down or stop. Never wait for your next appointment if you are worried about your baby's movements.
To find out which week of pregnancy you are in and what to expect, try our Pregnancy Calculator. If you are trying to work out when you conceived, use the Conception Calculator.
Frequently Asked Questions
How do I calculate my due date?
Add 280 days (40 weeks) to the first day of your last menstrual period. If you know your conception date, add 266 days instead. This calculator does it for you and adjusts for your cycle length.
Why is pregnancy counted from my last period?
Most people know when their last period started but not exactly when they conceived. Counting from the last period gives doctors a consistent starting point, which is why the first two weeks of "pregnancy" happen before conception.
Can my due date change?
Yes. Your doctor may change your due date after an early ultrasound if the baby's size suggests a different age than your period dates. After that, the due date usually stays the same.
What percentage of babies are born on their due date?
Only about 4% of babies are born on their exact due date. Most babies arrive within two weeks before or after it.
How many weeks is a full-term pregnancy?
A full-term pregnancy is 39 weeks 0 days to 40 weeks 6 days. Births from 37 weeks are considered early term, and after 42 weeks post term.
Is an ultrasound due date more accurate than LMP?
An early ultrasound, done in the first trimester, is usually the most accurate way to estimate a due date, especially if your periods are irregular or you are unsure of your LMP date.