Pregnancy Due Date Calculator
Estimate your due date using your last period, conception date, IVF transfer date, or an ultrasound scan — plus your current week of pregnancy, trimester, and key milestone dates.
ⓘ This is an estimate
Only around 1 in 20 babies arrive on their exact due date. A full-term birth anywhere from about 3 weeks before to 2 weeks after this date is completely normal.
✓ Four ways to calculate
Use whichever date you know most confidently — last period, conception, an IVF transfer, or a dated ultrasound scan.
⚠ Not a substitute for your care team
An early ultrasound is the most accurate way to confirm dates. Always follow your midwife or doctor's dating if it differs from this estimate.
Your last saved calculations
Calculate a due date and it'll be saved here automatically.
Three steps
Pick your dating method
Last period, conception, IVF transfer, or an ultrasound scan.
Enter the date(s)
Whichever you know most confidently.
See your full timeline
Due date, current week, trimester, and key milestones — instantly.
What This Tool Supports
We'd rather tell you upfront than have a number surprise you.
| Method | Formula used |
|---|---|
| Last menstrual period (LMP) | Naegele's rule: LMP + 280 days, adjusted for your cycle length |
| Conception date | Conception + 266 days |
| IVF Day-3 transfer | Transfer date + 263 days |
| IVF Day-5 transfer | Transfer date + 261 days |
| Ultrasound dating | Scan date + (280 − gestational age in days at scan) |
Common questions
How accurate is a due date calculator?
It's a standard obstetric estimate, not a guarantee — only about 1 in 20 babies are born on their exact due date. A full-term birth anywhere from roughly 3 weeks before to 2 weeks after this date is entirely normal. An early ultrasound is the most accurate way to confirm dates.
Why does my cycle length matter for the LMP method?
The standard due-date formula assumes a 28-day cycle with ovulation around day 14. If your cycles run longer or shorter, ovulation (and so conception) likely happened on a different day — adjusting for your actual cycle length gives a more personalised estimate.
Why is the IVF calculation different for Day 3 vs Day 5 transfers?
A Day-5 (blastocyst) embryo is already 5 days past conception at transfer, while a Day-3 embryo is only 3 days past conception — so the due date is counted forward from the transfer date by two fewer or two more days depending on which stage was transferred.
What are trimesters and when do they start?
Pregnancy is commonly split into three trimesters: first (weeks 1–13), second (weeks 14–27), and third (week 28 onward until birth). Each trimester is associated with different stages of development and different common symptoms.
Is this medical advice?
No. This tool provides a standard dating estimate for general information only. Always follow your midwife, doctor, or specialist's dating and advice, especially if it differs from this estimate.
Related reading
Trimester by trimester: what to expect
A general overview of pregnancy's three stages.
Read article →Why due dates are estimates, not deadlines
The statistics behind "only 1 in 20 babies arrive on time."
Read article →LMP vs ultrasound dating: which is more accurate
When your dates and your doctor's dates might differ.
Read article →This calculator provides a general estimate only and is not medical advice or a diagnosis. Always confirm your dates and any concerns with your midwife, doctor, or a qualified healthcare provider.