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Pregnancy Due Date Calculator

Estimate your due date from your last period or conception date, plus your gestational age and trimester dates. Free and private.

How to use

Estimate your baby’s due date from the first day of your last period, or from a known conception date. The calculator uses Naegele’s rule (last period plus 280 days), adjusts for your cycle length, then shows your gestational age, your trimester and when each trimester starts. Few babies arrive on the exact due date, so treat it as a guide.

  1. Enter your details.
  2. Results update instantly.
  3. Adjust the values to see how they change.

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Frequently asked questions

How is the due date calculated?

Naegele’s rule adds 280 days (40 weeks) to the first day of your last period. If your cycle is longer or shorter than 28 days, the date is shifted by the difference.

How accurate is a due date?

A due date is an estimate. Most babies are born between 37 and 42 weeks, and an early ultrasound can refine the date.

Is it free?

Yes. Everything is free, with no sign-up and no limits.

Is my data stored or sent?

No. Calculations run in your browser and nothing you enter is sent or stored.

Can I rely on these results?

They use standard published formulas and give estimates for general information.

For general information only. This is not medical advice. Talk to your doctor, midwife or dietitian about your own situation.