EDD Calculator – Estimated Date of Delivery

Written by Great Medico

Updated September 24, 2026 •2 min read

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The useful part of a fertility or pregnancy calculator is not just the answer; it is knowing the assumption behind the answer. EDD Calculator – Estimated Date of Delivery keeps that assumption visible.

What this calculator does

EDD Calculator – Estimated Date of Delivery uses Current date, Known pregnancy date, LMP / conception date, and Average cycle length to calculate EDD. It is built around the exact fields displayed in this plugin rather than a generic version of the topic. Where supported, it also shows Days until EDD so the primary result is easier to place in context. Pregnancy and fertility dates, hormone trends, and risk scores are estimates built around biologic averages. Cycle variation, ultrasound findings, assisted-reproduction details, and the individual pregnancy can matter more than a single calculated number.

How to use it

Enter or select Current date, Known pregnancy date, LMP / conception date, and Average cycle length. Use the units offered by the calculator and choose the option that matches the actual clinical or timing situation. Check date entries and laboratory units before relying on the output. For paired dates or serial measurements, keep them within the same menstrual cycle, pregnancy, or treatment episode as the calculator requires.

How the calculation works

The EDD calculator treats the entered date according to the selected “known” method. From LMP it adds 280 days plus the cycle-length adjustment; from a conception date it adds 266 days. It also compares the computed EDD with the entered current date to show days remaining.

Example

For example, if LMP is entered as January 1 with a 28-day cycle, the tool adds 280 days for the estimated delivery date and then counts the days between the entered current date and that EDD.

How to interpret the result

Treat the output as estimated date of delivery based on the assumptions encoded in this calculator. It can help with planning or understanding a measurement, but pregnancy and reproductive biology vary enough that the calculated date, ratio, or probability should be seen as a range or estimate rather than a guarantee.

Limitations and notes

Once an obstetric EDD has been established from the best available early data, it generally should not be repeatedly changed because later scans differ. This calculator cannot apply the full ultrasound redating rules or judge whether an LMP is reliable.