3 tricks to calculate the probable delivery date 2026

It is a logical reaction: from the moment it is discovered that a new little one is coming into the world, almost at the same time, interest begins in knowing what the due date will be and knowing when it will be possible to hold him or her in your arms. However, something that must be considered is that pregnancy is not an exact science, there are many factors that influence it and that cause the baby to be born one day or another.

In fact, the number of babies born on the day “indicated by the calendar” is quite low, around 5%. Of course, what can be done is an approximate count of the day or week of delivery, perhaps better said the latter, since there are people who consider that it would be better to talk about a “probable week” than a specific day.

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If what you are looking for is to know how to estimate that moment, we can help you here. To be able to predict more or less when your little one will arrive, you can use three methods. The first has to do with how long a pregnancy actually lasts under normal conditions, the second is based on using a calendar in the form of a table and, the last, on applying Naegele's Rule. Do you want to know how each one works? We explain it to you.

Method 1: the duration of pregnancy

Pregnancy in optimal conditions usually lasts about 280 days as a general rule.  That is, 40 weeks from the first day of the last period or 38 weeks from the fertilization of the egg (in a regular period, it usually happens 14 days after menstruation).

As it is somewhat impossible to know the exact day on which conception occurs, what is used is then the first day of the last period. We would add 280 days to that day to know when the child would be born.

Method 2: calendar in table form

Apart from the fact that the gynecologist can use a wheel-shaped calendar to calculate this date we are looking for, a different way is to use another table-shaped format like the one we leave you here.

In a normal assumption, as we have seen, the delivery date would be 40 weeks after the first day of the last menstruation. To quickly see what day it is, you can use this calendar. To use it, it is very simple: you have to look for the first day of the last period in the dates that are highlighted in bold. The number that appears immediately below will be the day; elmes indicates it in that same line, thus having the specific date.

One thing to keep in mind is that if it is a leap year we must add a day on any date after February 29.

For example: if the first day of the last period was July 12, the probable date we are looking for would be April 18 of next year.

Method 3: Naegele's Rule

This trick is very easy and is basically mathematical. It is a formula that is based on taking the first day of your last period, adding a year, subtracting three months and adding seven days. The result you obtain will be the probable date of the child's birth.

As a curious fact, this method is by no means something new. It owes its name to the obstetrician Franz Karl Naegele who created this rule in the 19th century.