Aisha K.
Mar 12, 2026
Clean layout and the results update instantly. Exactly what I needed for a quick planning check.
Health, Fitness & Wellness
Pregnancy Due Date Calculator from Last Period
Naegele: due date = LMP + 280 days (40 weeks).
Estimate due date and gestational age from days since last period (LMP). Estimates only—not a diagnosis or prescription.
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Tailored to your live inputs and result—guidance only, not professional advice.
- Interpret
Treat this as a planning estimate
Primary result: Days until due date = 36 wk. Re-run with optimistic and pessimistic inputs to understand the range—not just a single point.
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Plain-English guide
Terms & how it works
Confused by a field? Read the short definitions here while you use the tool.
Days since last period started
The “Days since last period started” value used in this tool’s formula. Adjust it to see results update live.
How this calculator works
Estimate due date and gestational age from days since last period (LMP). Estimates only—not a diagnosis or prescription. Naegele: due date = LMP + 280 days (40 weeks). Example: 28 days since LMP → ~252 days until due date, ~4 weeks pregnant.
Naegele: due date = LMP + 280 days (40 weeks).
Example: 28 days since LMP → ~252 days until due date, ~4 weeks pregnant.
When to use this Pregnancy Due Date
Common use cases
- Estimate due date and gestational age from days since last period (LMP).
- Sanity-check with this case: 28 days since LMP → ~252 days until due date, ~4 weeks pregnant.
- The relationship is: Naegele: due date = LMP + 280 days (40 weeks).
Localized examples
- Health, Fitness & Wellness: the example on this page uses the same formula as the widget.
What you get
- Fields: Days since last period started
- Naegele: due date = LMP + 280 days (40 weeks).
- Example on the page: 28 days since LMP → ~252 days until due date, ~4 weeks pregnant.
How to Calculate Pregnancy Due Date Step-by-Step
- 1Enter Days since last period started. Use the values you have, not a catalog average, unless that is all you know.
- 2Naegele: due date = LMP + 280 days (40 weeks).
- 3Worked case: 28 days since LMP → ~252 days until due date, ~4 weeks pregnant.
- 4If this number would change a drug, a diet, or a return-to-play call, take it to a clinician. The page never examined you.
Governing formula
Naegele: due date = LMP + 280 days (40 weeks).
28 days since LMP → ~252 days until due date, ~4 weeks pregnant.
Example: set Days since last period started = 28, then read the result.
Variable definitions
- daysSinceLmp
Days since last period started
The “Days since last period started” field. Default 28; typical range 0–280.
- The formula (Naegele: due date = LMP + 280 days (40 weeks).) does not see labs, medications, sleep, or injury history. A clinician does.
- Nothing here is uploaded for the calculation itself.
Frequently Asked Questions
Naegele: due date = LMP + 280 days (40 weeks).
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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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