Aisha K.
Mar 12, 2026
Clean layout and the results update instantly. Exactly what I needed for a quick planning check.
Unit Converters
Pregnancy Due Date: Last Period to Estimated Date
EDD = LMP + 280 days. Gestational age counts from LMP, not conception.
Naegele: EDD = first day of last period + 280 days (40 weeks). Cycles that are not 28 days shift this. Dating scans override the calendar. This is a planning date, not a booking.
First day of last period
Naegele +280 days
2026-12-06
Dating scans override the calendar.
Plain-English guide
Terms & how it works
Confused by a field? Read the short definitions here while you use the tool.
Last period date
The “Last period date” value used in this tool’s formula. Adjust it to see results update live.
Year
The “Year” value used in this tool’s formula. Adjust it to see results update live.
Month
The “Month” value used in this tool’s formula. Adjust it to see results update live.
Day
The “Day” value used in this tool’s formula. Adjust it to see results update live.
How this calculator works
Naegele: EDD = first day of last period + 280 days (40 weeks). Cycles that are not 28 days shift this. Dating scans override the calendar. This is a planning date, not a booking. EDD = LMP + 280 days. Gestational age counts from LMP, not conception. Example: LMP 1 Mar 2026 → EDD 6 Dec 2026.
EDD = LMP + 280 days. Gestational age counts from LMP, not conception.
Example: LMP 1 Mar 2026 → EDD 6 Dec 2026.
When to use this Due Date from LMP
Common use cases
- Naegele: EDD = first day of last period + 280 days (40 weeks). Cycles that are not 28 days shift this. Dating scans override the calendar. This is a planning date, not a booking.
- Sanity-check with this case: LMP 1 Mar 2026 → EDD 6 Dec 2026.
- The relationship is: EDD = LMP + 280 days. Gestational age counts from LMP, not conception.
Localized examples
- Unit Converters: the example on this page uses the same formula as the widget.
What you get
- Fields: Last period date, Year, Month, Day
- EDD = LMP + 280 days. Gestational age counts from LMP, not conception.
- Example on the page: LMP 1 Mar 2026 → EDD 6 Dec 2026.
How to Convert Due Date from LMP Step-by-Step
- 1Enter Last period date, Year, Month, then the remaining fields. Use the values you have, not a catalog average, unless that is all you know.
- 2EDD = LMP + 280 days. Gestational age counts from LMP, not conception.
- 3Worked case: LMP 1 Mar 2026 → EDD 6 Dec 2026.
- 4Check which dictionary the other person is using — US or UK, decimal or 1,024 — then trust the number.
Governing formula
EDD = LMP + 280 days. Gestational age counts from LMP, not conception.
LMP 1 Mar 2026 → EDD 6 Dec 2026.
Example: set Last period date = 2,026, Year = 2,026, Month = 3, then read the result.
Variable definitions
- value
Last period date
The “Last period date” field. Default 2026; typical range 2020–2032.
- year
Year
The “Year” field. Default 2026; typical range 2020–2032.
- month
Month
The “Month” field. Default 3; typical range 1–12.
- day
Day
The “Day” field. Default 1; typical range 1–31.
- The conversion (EDD = LMP + 280 days. Gestational age counts from LMP, not conception.) does not pick US vs UK gallons, SI vs binary megabytes, or Mach at altitude for you. Read the footnote on the page.
- Nothing here is uploaded for the calculation itself.
Frequently Asked Questions
Tell the midwife. The 280-day rule assumes a 28-day cycle.
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Reviews & Ratings
See what others think about this tool, then leave your own rating to help improve CalculioHub.
4.8
out of 5.0
4 reviews
Daniel R.
Feb 28, 2026
Very usable on mobile. Would love a save/export option later, but the math feels solid.
Priya S.
Feb 3, 2026
The FAQ section answered my questions before I even had to search. Smooth dark mode too.
Marcus L.
Jan 19, 2026
Simple inputs, clear outputs. This replaced three bookmarks I used to juggle.
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