Fetal Age on a Given Date Calculator

This calculator estimates the age of a fetus on a particular date based on the last menstrual period (LMP) or a known estimated due date (EDD). The calculator assumes a standard cycle length of 28 days with ovulation around day 14, but you may adjust the cycle length if known.

Choose dating input

Use LMP Use known EDD (instead of LMP)

If you enter a known EDD, the calculator back-calculates an LMP (using the cycle length setting) to estimate gestational and conceptual age on the date in question.

First day of last menstrual period (LMP)

Known estimated due date (EDD)

EDD is treated as 40 weeks 0 days gestational age. Cycle length is used only for back-calculating an LMP and estimating conceptual age.

Cycle length (days, optional)

Default is 28 days if left unchanged or blank.

Date to estimate fetal age

Conceptual age = time elapsed since the estimated day of conception.
Gestational age (or “menstrual age”) = time elapsed since the first day of the last normal menstrual period.

Created: 11/10/2002, Updated 2026 Mark A. Curran, M.D.

All calculations must be confirmed before use. The suggested results are not a substitute for clinical judgment. Neither Perinatology.com nor any other party involved in the preparation or publication of this site shall be liable for any special, consequential, or exemplary damages resulting in whole or part from any user's use of or reliance upon this material.