Pregnancy Calculator
Estimates how far along a pregnancy is and builds a full schedule: due date (280 days from the last period), current week and day, trimester boundaries and key milestone dates. Works from a due date, last menstrual period or conception date.
TheCalculators — Pregnancy Calculator
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Current Gestational Age
20 weeks + 0 days
Due March 28, 2027 · calculated from your due date
- Due date (40 weeks)
- March 28, 2027
- Current week
- Week 21 of 40
- Trimester
- Second (weeks 14–27)
- Days pregnant
- 140 of 280 days (50%)
- Estimated conception
- Jul 5, 2026
Pregnancy progress
- Days completed140.00
- Days remaining140.00
Key pregnancy dates
Gestational age is counted from the last menstrual period; conception happens ~2 weeks later.
Fewer than 4% of babies arrive on their exact due date — about 60% arrive within a week and ~90% within two weeks. Your doctor's ultrasound-based estimate is the most accurate. Estimates for informational purposes only — not medical advice.
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Formula
Due date = LMP + 280 days (+ cycle length − 28) · Conception ≈ LMP + 14 days · Due = conception + 266 days
- • Naegele's rule: add 280 days (40 weeks) to the first day of the last menstrual period.
- • Cycle lengths longer or shorter than 28 days shift the estimate by the difference.
- • Working backwards from a due date, conception is placed 266 days earlier (38 weeks after fertilization).
Pro tips
- • The 12-week ultrasound is the most accurate way to date a pregnancy — earlier than LMP math.
- • Trimester boundaries: 1st = weeks 1–13, 2nd = 14–27, 3rd = 28–40.
- • Any date between 37 and 42 weeks counts as full term.
FAQ
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