Method
Using the last menstrual period, this calculator adds 280 days and adjusts by the selected cycle length. Using conception date, it adds 266 days. These are common estimating methods, not a diagnosis or confirmation of gestational age.
Assumptions and limitations
Due dates are approximate. Cycle length, ovulation timing, ultrasound findings and clinical assessment can change dating. Contact a qualified healthcare professional for pregnancy care or medical concerns.
References
- NHS: dating pregnancy and scans, accessed 2026-05-13.
- ACOG: Methods for Estimating the Due Date, accessed 2026-05-13.
- MedlinePlus: When you pass your due date, accessed 2026-05-13.
Last reviewed: 2026-05-13