Health
Due dates are typically estimated from the first day of the last menstrual period using Naegele's rule, assuming a 28-day cycle with ovulation around day 14. Ultrasound dating by a clinician is more accurate when available.
Due dates are typically estimated from the first day of the last menstrual period using Naegele's rule, assuming a 28-day cycle with ovulation around day 14. Ultrasound dating by a clinician is more accurate when available.
Only about 5% of babies arrive on the exact estimated date; a window of several weeks is normal.
CalculatorCamp provides an educational LMP-based estimate. Always follow obstetric care and ultrasound guidance for medical decisions.
Enter the first day of your last period and cycle length if the form allows. Calculate to see estimated due date and gestational age if shown.
This pregnancy due date calculator applies the standard relationship below. Intermediate values are kept at full precision; only the displayed result is rounded.
Due date ~ LMP + 280 days (40 weeks) for standard 28-day cycle adjustments
No. It is an estimate; ultrasound and clinical assessment refine dating.
No. Not a replacement for prenatal care.
Use cycle length field if present; otherwise discuss with your clinician.
Yes.
The factors and formulas used by this tool follow these references:
Health and fitness results are estimates for general education and planning. They are not medical advice and do not replace an assessment by a doctor, registered dietitian, or other qualified professional.
Last reviewed: September 2026. Found an error? Tell us and we will correct it.
More calculators in Health.