SVCS

Pregnancy Due Date Calculator

Estimated due date by Naegele’s rule, adjusted for cycle length.

Important: This calculator is for general information only and is not a medical diagnosis or advice. All calculations run in your browser — nothing is sent or stored. The estimate does not replace prenatal care from an OB-GYN.

Frequently asked questions

How is the due date calculated?

By Naegele’s rule — the estimate is the first day of your last period plus 280 days (40 weeks). If your cycle differs from 28 days, we add the difference.

How accurate is the due date?

Only about 4% of babies arrive exactly on the due date. Most births happen within two weeks either side. A first-trimester ultrasound gives a more precise estimate.

Can I calculate from the conception date?

Yes — from conception the due date is roughly +266 days. This calculator uses the last period, as that date is more commonly known.

← All health calculators