Due Date Calculator
Calculate your estimated due date, gestational age and trimester from your LMP.
Enter your LMP to get your estimated due date and current gestational age.
Due Date Calculator on True Calculator gives you an instant, accurate answer with no sign-up and no app install. Calculate your estimated due date, gestational age and trimester from your LMP. Every result shows the formula and a worked example so you can verify the calculation yourself, and all values are computed in your own browser — your numbers never leave your device.
Popular uses: due date calculator · baby due date calculator · pregnancy due date
How We Calculate
This calculator uses medically reviewed formulas verified by our team. All calculations are performed instantly in your browser using JavaScript — no data is sent to any server.
We use WHO-recommended formulas and medical standards for health calculations. Results are estimates, not medical advice — always consult a doctor for health decisions.
When to Use This Calculator
Use the due date calculator from the very first weeks of pregnancy to establish a working date before your first scan appointment. The estimated delivery date drives many practical decisions in India: booking maternity hospitals, planning maternity leave with your employer, scheduling the first-trimester scan and screening tests, and telling relatives and colleagues when to expect the baby. Because the tool also shows gestational age in weeks and days, it doubles as a quick 'what week am I in' reference throughout the nine months — handy when doctors ask your week at appointments or when reading about trimester milestones. It is also a gentle reality check on how much time remains, which helps with preparation. The result is an estimate following the 40-week convention; only a doctor can confirm your true dates.
How to Use This Calculator
- Step 1: Pick the first day of your last period in the date field.
- Step 2: Read the estimated due date — the LMP plus 280 days.
- Step 3: Check your current gestational age in weeks and days and the total days pregnant.
- Step 4: Note the trimester and weeks remaining to plan scans and maternity leave.
Worked Example
A woman in Delhi enters 1 March 2026 as her LMP. The calculator adds 280 days and returns 6 December 2026 as the estimated due date. If she checks the tool again on 14 August, her gestational age shows 26 weeks and 3 days — 185 days of pregnancy — placing her in the second trimester with about 14 weeks left. A different LMP of 10 February 2026 produces a due date of 17 November 2026. Every date follows the standard rule that pregnancy lasts 40 weeks counted from the LMP, which is exactly how clinics first date a pregnancy.
Tips and Common Mistakes
- •Tip 1: Save your LMP in a notes app the moment your period starts — it is the single date every antenatal calculation uses.
- •Tip 2: Expect the doctor to keep or adjust your due date based on the first-trimester ultrasound, which is more precise.
- •Tip 3: Plan leave and travel around the 38-week mark rather than the exact due date, since birth can happen any time after 37 weeks.
- ✗Mistake 1: Using a conception date in place of the LMP — mixing the two counting systems shifts results by about two weeks.
- ✗Mistake 2: Recalculating with a remembered-but-uncertain LMP; a wrong LMP silently misdates the whole pregnancy.
Frequently Asked Questions
How is the due date calculated?
The calculator takes the first day of your last period and adds 280 days, the standard 40-week length of pregnancy. This is the Naegele's rule used by doctors worldwide.
Why is my LMP important?
Pregnancy is measured in weeks from the LMP, not from conception. Knowing your LMP lets anyone estimate gestational age and due date consistently, which is why clinics always ask for it.
Will my baby be born on this date?
Probably not exactly. Only a small minority of babies arrive on their calculated date; births between 37 and 42 weeks are considered full term, so a range of about five weeks is normal.
Is the 40-week rule the same in India?
Yes. Indian obstetricians use the same international standards — 40 weeks from the LMP — and will usually confirm or adjust the date using an ultrasound scan in the first trimester.
What if I don't remember my LMP?
An early ultrasound is the best alternative for dating the pregnancy. If you know only the month, a scan or your doctor's assessment will give a more reliable due date than any calculation.
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