LMP dating
Sample
Last period start date
What you get
Gestational age summary and trimester context (educational).
Pregnancy Calculator
Pregnancy dating on this page follows a common obstetric rule of thumb: count about 280 days (40 weeks) from the first day of the last menstrual period, then label trimester by gestational week. Clinics often refine the due date after an early ultrasound, so treat the numbers here as an educational starting point—not a care plan. Your typed dates stay in the browser.
Pregnancy Calculator
YearMonthDay
Due date (280d rule)
Mar 8, 2026
Gestational age
~74 weeks
Trimester
3
These tools provide general fitness estimates only and are not a substitute for professional medical advice.
How to Use This Tool
- Enter the first day of the last menstrual period.
- Review EDD and approximate gestational age.
- See your clinician for dating and care.
Features
- 280-day Naegele-style EDD from LMP
- Trimester label
- Educational only
Example
Frequently Asked Questions
How is due date estimated?
From last menstrual period we apply a common 280-day (40-week) rule and derive gestational weeks/trimester. Ultrasound dating from your clinician takes priority.
Is this medical advice?
No. This calculator is for general education and planning only. Always consult a qualified clinician for personal health decisions.
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