SwiftCalcTools

Due Date Calculator — Pregnancy Due Date Calculator

Calculate your pregnancy due date from the last menstrual period (LMP) or conception date. Track your pregnancy week by week.

❤️ Health & Fitness ✅ Free

By SwiftCalcTools Editorial Team · Formula verified

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How to Use Due Date Calculator

  1. 1Enter the required values in the input fields above.
  2. 2Click the Calculate button or results update instantly as you type.
  3. 3View your results in the output panel below the inputs.
  4. 4Adjust any values to recalculate instantly.

Frequently Asked Questions

The Estimated Due Date (EDD) is calculated using Naegele's Rule: add 40 weeks (280 days) to the first day of your last menstrual period (LMP). This assumes a 28-day cycle with ovulation on day 14. Only about 5% of babies are born on their exact due date — most are born within 2 weeks before or after.
Gestational age is the age of the pregnancy counted from the first day of the last menstrual period (LMP), not from conception. So at conception (typically week 2), gestational age is already 2 weeks. A full-term pregnancy is 40 weeks gestational age (38 weeks from conception).
1st Trimester: Weeks 1–13 (organ formation, highest miscarriage risk). 2nd Trimester: Weeks 14–27 (growth phase, most women feel best). 3rd Trimester: Weeks 28–40 (rapid growth, preparation for birth). "Full term" is weeks 39–40; "early term" is 37–38 weeks.
For IVF with Day 5 blastocyst transfer: EDD = transfer date + 261 days (280 − 14 − 5). For Day 3 embryo: EDD = transfer date + 263 days (280 − 14 − 3). The IVF due date is more accurate than LMP-based calculation since fertilisation and implantation dates are precisely known.