Health calculator
Pregnancy Due Date Calculator
Estimate a pregnancy due date from the first day of the last menstrual period.
Formula
Due date estimate
Due dates are estimates. Ask a qualified clinician for pregnancy dating and medical decisions.
Estimated due date = LMP + 280 days
A last menstrual period on 1 January gives an estimated due date around 8 October.
FAQs
How is the due date estimated?+
A common estimate adds 280 days to the first day of the last menstrual period.
How does the Pregnancy Due Date Calculator calculate the result?+
It uses the Due date estimate: Estimated due date = LMP + 280 days. A last menstrual period on 1 January gives an estimated due date around 8 October.
What information do I need to use the Pregnancy Due Date Calculator?+
Estimate a pregnancy due date from the first day of the last menstrual period.
How accurate is the Pregnancy Due Date Calculator?+
Pregnancy Due Date Calculator applies the formula and assumptions shown on this page. Results may be rounded for readability, so verify changing rates, thresholds, medical guidance, or legal rules with the cited source or a qualified professional.
What should I check before using the Pregnancy Due Date Calculator result?+
Check that the units, dates, rates, and assumptions match your situation. Change one input at a time to understand which values have the largest effect on the result.
Health guide
How to use the Pregnancy Due Date Calculator
Estimate a pregnancy due date from the first day of the last menstrual period. The page also explains the due date estimate and shows a practical example: A last menstrual period on 1 January gives an estimated due date around 8 October.
- 1
Enter your details
Enter the first day of the last menstrual period, then complete any other fields shown in the calculator.
- 2
Check the calculation
Review the result alongside the due date estimate: Estimated due date = LMP + 280 days.
- 3
Compare scenarios
Change one or more inputs to see how they affect the pregnancy Due Date Calculator result before you use the estimate.
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