What is the Pregnancy Due Date Calculator?
Estimate a pregnancy due date from the first day of the last menstrual period (Naegele’s rule). Our health and fitness calculators use validated, published equations — such as Mifflin-St Jeor for metabolic rate and the U.S. Navy method for body fat — to give you a solid starting point for training and nutrition.
How to use the Pregnancy Due Date Calculator
- Enter your first day of last period, your average cycle length.
- Results update automatically as you type; you can also press Calculate.
- Read the output: estimated due date, conception (approx.), end of first trimester.
- Use the 📊 chart to see the result visually, then copy or share it.
Formula and method
Worked example
With first day of last period = 2026-03-01, average cycle length = 28 days, the Pregnancy Due Date Calculator returns estimated due date: Sunday, December 6, 2026; conception (approx.): Sunday, March 15, 2026; end of first trimester: Saturday, June 6, 2026.
Tips for better results
- Equations estimate population averages; your individual numbers may differ.
- Track trends over weeks rather than reacting to a single reading.
- Pair calculators with professional guidance for medical conditions, pregnancy or major diet changes.
⚠️ This tool provides general information and is not medical advice. It is not a substitute for diagnosis or treatment by a qualified healthcare professional.
Frequently asked questions
What does the Pregnancy Due Date Calculator do?
Estimate a pregnancy due date from the first day of the last menstrual period (Naegele’s rule).
How is it calculated?
The Pregnancy Due Date Calculator uses this method: Due date = LMP + 280 days (+ cycle length − 28).
Can you show an example?
With first day of last period = 2026-03-01, average cycle length = 28 days, the Pregnancy Due Date Calculator returns estimated due date: Sunday, December 6, 2026; conception (approx.): Sunday, March 15, 2026; end of first trimester: Saturday, June 6, 2026.
Is the Pregnancy Due Date Calculator accurate?
It uses standard published formulas and is tested against known values, but results are estimates for guidance. This tool provides general information and is not medical advice. It is not a substitute for diagnosis or treatment by a qualified healthcare professional.
Is this tool free and private?
Yes — the Pregnancy Due Date Calculator is completely free with no sign-up, and it runs entirely in your browser, so the values you enter are never uploaded to our servers.
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