Due Date Calculator — Estimate Your Baby's Due Date
Enter your LMP, conception date, or IVF transfer date and get your estimated due date instantly.
Enter a date above to calculate your due date.
These are estimates, not medical advice — consult your healthcare provider.
What is due date calculator?
The due date calculator estimates your baby’s expected arrival using three methods: last menstrual period (LMP), conception date, or IVF embryo transfer date. The standard LMP method applies Naegele’s rule — adding 280 days (40 weeks) to the first day of your last period — and adjusts for cycle lengths between 20 and 45 days. If you know your conception date, the tool uses the 38-week (266-day) window from fertilisation instead. For IVF pregnancies, the embryo’s known age at transfer is subtracted from that same 266-day window to account for the days already elapsed.
Due dates are estimates, not predictions. Research consistently shows that only about 5% of babies are born on their calculated EDD; the vast majority arrive within a two-week window on either side. First-trimester ultrasound measurements often provide a more accurate dating than menstrual history alone, and your provider may update your due date based on those findings. Factors such as irregular cycles, uncertainty about the LMP, and individual variation in fetal development all contribute to the normal spread around any estimated date.
All calculations run locally in your browser — no dates or personal information are transmitted to any server. The results shown here are for informational purposes only and are not a substitute for personalised medical advice from a qualified healthcare provider.
When to use a due date calculator
- Estimate EDD from your last period — The most common method — enter the first day of your last menstrual period and your typical cycle length. The calculator applies Naegele's rule (LMP + 280 days, adjusted for cycle length) to produce your estimated due date.
- Calculate due date from a known conception date — If you know when conception occurred — from ovulation tracking, a fertility monitor, or timing — enter that date directly. The tool adds 266 days (38 weeks) to give your EDD without needing your LMP.
- Due date after an IVF embryo transfer — For IVF pregnancies, select the transfer method and enter your embryo transfer date. Choose Day 5 (blastocyst) or Day 3 (cleavage-stage) — the calculator subtracts the embryo's age from the standard 266-day window to find your EDD.
- Track current gestational age and trimester — The results panel shows your current gestational age in weeks and days as of today, the trimester you are in, and how many weeks remain until your estimated due date — a quick at-a-glance pregnancy progress summary.
How to use the Due Date Calculator — Estimate Your Baby's Due Date
- Choose your calculation method — Select 'Last period (LMP)', 'Conception date', or 'IVF transfer' using the method buttons at the top of the calculator. The form updates to show the relevant inputs for each method.
- Enter the relevant date (and optional parameters) — Type or pick the date that matches your chosen method — either your last period, conception date, or embryo transfer date. For LMP, you can also adjust the cycle length (default 28 days, range 20–45). For IVF, choose Day 5 or Day 3 transfer.
- Read your estimated due date and pregnancy progress — Your estimated due date appears instantly, along with the day of the week it falls on, your current gestational age in weeks and days, your trimester, and the number of weeks remaining. Use the 'Copy summary' button to save the result to your clipboard.
Worked examples
LMP January 1, 2026 (28-day cycle)
Input: Method: LMP / Date: 2026-01-01 / Cycle: 28 days
Output: Estimated due date: October 8, 2026Naegele's rule: LMP + 280 days. A standard 28-day cycle requires no adjustment.
Conception date January 1, 2026
Input: Method: Conception date / Date: 2026-01-01
Output: Estimated due date: September 24, 2026Conception to delivery is 266 days (38 weeks), two weeks shorter than the LMP window.
IVF Day-5 transfer January 1, 2026
Input: Method: IVF transfer / Date: 2026-01-01 / Embryo age: Day 5
Output: Estimated due date: September 19, 2026Day-5 blastocysts are 5 days old at transfer, so the window is 266 − 5 = 261 days from transfer date.