Due Date from Conception Calculator

Estimated due date = conception + 266 days. Not medical advice.

Inputs

Result

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How to use this calculator

  • Enter known or estimated conception date.
  • Read estimated due date.

About this calculator

A "term" pregnancy is 266 days from conception (38 weeks), equivalent to 280 days from LMP. Conception date is rarely known precisely; LMP-based dating is more common in clinical practice. Not medical advice.

Frequently asked

Why 266 not 280?+
Because LMP is conventionally ~14 days before conception. Both formulas (LMP+280, conception+266) give the same answer.
How accurate?+
±1-2 weeks for most pregnancies. Ultrasound dating in the first trimester is the most accurate clinical method.
How likely is delivery on the exact due date?+
About 5%. Most births are within ±10 days. ~10% are post-term (after 42 weeks).
Medical advice?+
No — this is a date calculator. Use with prenatal care, not in place of it.
What if conception was IVF?+
IVF dating is precise — count from the embryo-transfer date plus implantation offset (~5 days for blastocyst, ~3 for cleavage-stage). Your fertility clinic provides exact dating.

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