Pregnancy Due Date Calculator

Free Pregnancy Due Date Calculator

This pregnancy due date calculator estimates when your baby is due. Choose the method that fits your situation — first day of your last menstrual period (LMP), conception date, or IVF transfer — enter the reference date, and the tool shows your estimated due date, your current gestational age in weeks and days, your trimester, and key milestones along the way.

How the Calculation Works

A typical pregnancy lasts about 40 weeks (280 days) measured from the first day of the last menstrual period. This calculator uses several standard methods:

• LMP method (Naegele's rule) — add 280 days to the first day of your last period, adjusted for cycle length if it differs from 28 days
• Conception date method — add 266 days to the date of conception
• IVF 3-day transfer — add 263 days to the transfer date (266 minus 3)
• IVF 5-day transfer — add 261 days to the transfer date (266 minus 5)

How to Use the Calculator

Select the method you have data for, enter the reference date, and adjust the cycle length if it differs from the standard 28 days (only used for the LMP method). The result updates instantly. You will see the estimated due date, where you are right now in the pregnancy (e.g. "12 weeks 3 days"), and the current trimester.

Pregnancy Milestones at a Glance

The milestone table shows the major checkpoints relative to your due date:

• Conception (estimated) — about 2 weeks after the start of your last period
• End of first trimester (13 weeks) — first ultrasounds and screenings
• End of second trimester (27 weeks) — many anatomy and growth scans
• Full term begins (37 weeks) — labour any time after this is considered full-term
• Estimated due date (40 weeks) — only about 5% of babies are born on this exact date

Important Note

This calculator gives an estimate based on standard formulas. Actual delivery can occur any time from week 37 to week 42, and your healthcare provider may adjust the due date after an ultrasound — especially if the dating ultrasound is done in the first trimester. Always confirm timing with your doctor or midwife.

Privacy

The calculator runs entirely in your browser. Nothing you enter is sent to a server, stored, or shared. It is 100% private, free, and requires no sign-up.

Frequently Asked Questions

How accurate is the due date?

Only about 5% of babies are born exactly on the estimated due date. Most arrive within two weeks before or after, and 90% are born between 37 and 42 weeks. The estimate is a useful planning target, not a precise prediction.

What if I don't know the date of my last period?

Use the conception-date method if you can estimate that, or speak to your healthcare provider — an early ultrasound (around 8-12 weeks) can date the pregnancy very accurately.

Does cycle length really matter?

Yes, for the LMP method. If your cycle is longer than 28 days, ovulation happens later, so conception happens later — and the due date shifts. The calculator adjusts for this automatically when you set the cycle length.

Is this medical advice?

No. This is an educational tool for estimating a due date based on standard formulas. Always work with a qualified healthcare provider for medical decisions during pregnancy.