Can I use my conception date instead?

Yes. Select the Conception Date option and enter when you think conception occurred. The calculator adds 266 days (38 weeks) to give your estimated due date.

Due Date Calculator

Calculate your estimated due date, weeks pregnant and trimester. Enter your last period date or conception date for instant results.

First day of last menstrual period

About This Tool

What it does

Calculates your estimated due date using Naegele's rule — the standard method used by midwives and obstetricians worldwide. Also shows weeks pregnant, trimester and key milestone dates throughout your pregnancy.

Who it's for

Expectant parents wanting a quick estimate before their first midwife appointment. Used in the UK, US, Australia, Canada, Singapore, India and worldwide.

Your privacy

All calculations happen entirely in your browser. No dates or health data is transmitted or stored. ToolBullet never collects your health data.

⚠️ For informational purposes only. This calculator provides an estimate. An early ultrasound scan provides the most accurate due date. Always follow guidance from your midwife, obstetrician or GP. Sources: NHS, ACOG.

Frequently Asked Questions

How is my due date calculated?

The standard method (Naegele's rule) adds 280 days (40 weeks) to the first day of your last menstrual period. An early ultrasound scan at 8-12 weeks provides the most accurate due date and may adjust this estimate.

What week does each trimester start?

First trimester: weeks 1-12. Second trimester: weeks 13-26. Third trimester: week 27 until birth. Most babies arrive between weeks 37 and 42.

How accurate is an estimated due date?

Only around 5% of babies are born on their exact due date. Most arrive within two weeks either side. An early scan between 8 and 12 weeks provides the most accurate dating.

Can I calculate from my conception date?

Yes. Select Conception Date and enter when conception occurred. The calculator adds 266 days (38 weeks) to give your estimated due date.

Due Date Calculator

About This Tool

Frequently Asked Questions

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