Best Free Online OB Wheel Calculator

The OB Wheel Calculator is a versatile pregnancy tool used to calculate important pregnancy dates such as the estimated due date (EDD), gestational age, and conception date. It can work from various reference points including the last menstrual period (LMP), ultrasound data, or known conception dates. This digital tool replicates the traditional OB wheel’s functions and often includes additional features like accuracy for leap years and combining multiple methods for better estimations. It streamlines pregnancy care by providing quick and reliable calculations for expectant mothers and healthcare professionals.

OB Wheel Calculator

Estimate conception, due date, gestational age & trimester — fully offline
Choose first day of your last period.
Default 28 days. Adjust if your cycles are longer/shorter to shift conception estimate.
Example: LMP = 10 August 2025 → EDD = 17 May 2026

Results

Well-formatted dates, gestational age and trimester stage

Estimated Date of Conception

Estimated Due Date (EDD)

Current Gestational Age

Trimester

Notes & Interpretation

Naegele’s rule used for EDD: EDD = LMP + 280 days. Conception estimated as LMP + (cycle – 14) + 14 days ≈ LMP + (cycle – 28) + 14 days (default cycle 28 → conception ≈ LMP + 14 days).

Disclaimer: This OB Wheel Calculator is intended for informational and educational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment. Always consult your healthcare provider for personalized medical guidance. We do not assume any liability for decisions made based on the calculator’s results.
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