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Pregnancy Due Date (Naegele's Rule) — result sheet
Estimate a due date as 280 days after the first day of the last menstrual period.
Inputs used
Results
Visual chart
Breakdown
Calculation steps
Returned data table
Formula and methodology
Formula: EDD = LMP + 280 days.
Naegele's rule adds 280 days (40 weeks) to the last menstrual period. Real gestation varies and clinical dating uses ultrasound; this is an arithmetic estimate for planning only.
This result follows the calculator's declared inputs, precision, validation boundaries, and model limits.
Input contract
- First day of last period — Gregorian date; result is an estimate, not a medical determination.
Worked example
| Input | Value |
|---|---|
| First day of last period | 2024-01-01 |
2024-10-07; 280 days later.
Assumptions and limits
- Regular 28-day cycles are assumed; irregular cycles shift the estimate.
- Gregorian calendar dates from 0001-01-01 to 9999-12-31; result must stay in range.
- Educational estimate only, not medical advice or a diagnosis.
Calculator note
Source and methodology
Use the official WorldCalculate methodology policy for the source, formula, precision, and boundary standards behind this calculator.
Planning estimate, not financial, medical, legal, or professional advice. © WorldCalculate — reuse with attribution. Built and curated by Hassan ALRowaie.
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