# Naegele's Rule Calculator

The Naegele's Rule Calculator calculates the due date of a woman's pregnancy based on the first day of the last menstrual cycle that a woman had.

Based on the first day of the last menstrual cycle a woman has had, the due date for the pregnancy is predicted by adding 9 months to the date plus 7 days. Another way of viewing it is just to add a year to the date of the first day of the last menstrual cycle, subtracting 3 months, and then adding 7 days to it.

This calculator calculates for leap year status. So on years when there is a leap year, meaning there is a February 29th, the calculator compensates for this. So if a woman's last menstrual cycle was on May 22, 2015, her due date will be February 29, 2016, which is a leap year. But if her last menstrual cycle was on May 22, 2016, her due date will be March 1, 2017, since 2017 isn't a leap year and thus doesn't have a February 29th. So the calculator adjusts for each and every leap year, so it's accurate with respect to that.

There are some tricky calculations to consider when using Naegele's rule. One thing is say, you have the date May 31 as the first day of a woman's last menstrual period. Adding 9 months to this date gives us February 31. However, this date does not exist. February only has 28 days in a non-leap year and 29 days in a leap year. Therefore, adding 9 months to May 31 in a non-leap year gives us March 3. Then, to get the final date, we add 7 days to this date, which gives us March 10. So the estimated date of delivery would be March 10 in a non-leap year. For a leap year adding 9 months to May 31 gives us March 2. Adding 7 days to March 2 gives us March 9 in a leap year. So, this is how this calculator handles this. The calculator always adds 9 months and then 7 days to the first day of a woman's last menstrual period.

The result of 9 months and 7 days added to the first day of the last menstrual cycle is approximately 280 days from the start of the last menstrual cycle.

Realize that Naegele's calculator, like any other due date calculator, is not 100% accurate. There are all kind of complications that can occur during pregnancy which make it absolute impossible to calculate a due date from months behind. Naegele's calculator is an approximator that gives a due date more or less near the target. One reason it's an approximator is that it assumes a woman's menstrual period is 28 days, which is the average cycle length of a woman's menstrual period. However, this is not always the case. It can be longer or shorter than this.

The reason this calculator is included is because many aspects of pregnancy and health and healthcare in general uses many electronic tools
and components as predictors or markers for health. Many electronic tools are used in pregnancy, so this calculator can serve as a guide in the design of an electronic tool to predict pregnancy
Being that health and electronics are being more interwined as ever before, all calculators predicting or forecasting health can be used in the design of electronics for health.

Related Resources

Bartholomew's Rule of Fourths Calculator

GPA System Obstetric History Calculator

TPAL System Obstetric History Calculator

GTPAL System Obstetric History Calculator

Autosomal Recessive Inheritance Calculator

Autosomal Dominant Inheritance Calculator