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Conception Date Calculator

Estimated date of conception from a due date or LMP.

Estimate the date of conception either from a known due date (subtracting 266 days) or from the first day of your last menstrual period.

Priya Venkatesan By Priya Venkatesan
Reviewed by Dr. Helena Ortiz
Published Last reviewed 1 min read

Inputs

days

Results

Enter values and click Calculate to see results.
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How to use this calculator

  1. Fill in the inputs above using the units you already have.
  2. Values update automatically as you type — no submit button needed.
  3. Hover any result row for the underlying formula and intermediate values.

Formula

From due date: conception ≈ due date − 266 days. From LMP: conception ≈ LMP + (cycle length − 14) days.

In depth

Estimate the date of conception either from a known due date (subtracting 266 days) or from the first day of your last menstrual period.