Pregnancy Due Date Calculator
Your estimated due date by ACOG's convention, how far along you are today, and the dates you reach early, full and late term.
Estimated due date
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| Milestone | Date |
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Common questions
How is a due date calculated?
By convention, 280 days (40 weeks) after the first day of your last menstrual period (ACOG). This assumes a 28-day cycle with ovulation on day 14; for regular cycles of other lengths, add or subtract the difference.
Can I calculate from conception instead?
Yes: conception date + 266 days gives the same estimate.
How accurate is the due date?
It is an estimate. ACOG notes only about half of people recall their LMP accurately; a first-trimester ultrasound confirms or revises the date and is what your clinician will use.
What do early term, full term and late term mean?
ACOG and SMFM: early term 37 0/7–38 6/7 weeks, full term 39 0/7–40 6/7, late term 41 0/7–41 6/7, postterm 42 0/7 and beyond.
How it's computed
EDD = LMP + 280 days + (cycle length − 28), or conception + 266 days. Gestational age is counted from the LMP (for a conception date, conception − 14 days, adjusted the same way). Milestones use ACOG's term definitions. Use your clinician's ultrasound-based date if you have one.
Sources
- ACOG Committee Opinion No. 700: Methods for estimating the due date. Obstet Gynecol. 2017;129(5):e150-e154. www.acog.org
- ACOG Committee Opinion No. 579: Definition of term pregnancy (2013). www.acog.org
- Merck Manual Professional — Gestational age (LMP + 280 days + (cycle length − 28); conception + 266 days). www.merckmanuals.com
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