Due date calculator
Find your baby's due date from your last period, the day you conceived, or your IVF transfer.
Not sure? Keep 28 days. It's the most common.
Your estimated due date is
- Baby was likely conceived around
- Second trimester starts
- Third trimester starts
- Full term starts (39 weeks)
Saved. Other tools on this site will fill it in for you. It stays on this phone only.
How is a due date calculated?
Doctors count 40 weeks (280 days) from the first day of your last period. This assumes a 28-day cycle. If your cycle is longer or shorter, the date moves by the same number of days. Only about 1 in 20 babies arrive exactly on their due date, so think of it as the middle of a window, not a promise.
How we calculate this
Last period: first day of last period + 280 days, plus (your cycle length − 28) days. Conception: conception date + 266 days. IVF: transfer date + 261 days for a day-5 embryo, or + 263 days for a day-3 embryo. This is Naegele's rule, the method most doctors use. An early ultrasound may change your date, and your doctor's date is the one to follow.
Questions moms ask
How accurate is a due date calculator?
It gives the same estimate most doctors start with. Most babies are born within two weeks either side of the due date. An early ultrasound is the most accurate way to date a pregnancy.
Why do doctors count from my last period and not from conception?
Most people know the date of their last period but not the exact day they conceived. So pregnancy is counted from the period. That's why you're already about 2 weeks pregnant on the day you conceive.
My cycle is irregular. Can I still use this?
Yes, but the date is less certain. Use your average cycle length. If your cycles vary a lot, an early ultrasound will give a better date.
Can my due date change?
Yes. If an early ultrasound shows your baby is a different size than expected, your doctor may move your due date.
Is my information saved or sent anywhere?
No. Everything is calculated on your phone. If you tap Save, the date is stored only on this device so other tools can use it.
Related tools
This tool gives an estimate, not medical advice. Every pregnancy and every baby is different. If you're worried about anything, talk to your doctor or midwife.