ISo with the plain odds of 100:105 which roughly translates to 51.2% chances of having a boy. For those placing bets, the safe bet is that a younger or first-time mom will have a boy.

Many people consider these odds the best guess, but how can you tell what is going on for your baby?

One theory suggests the following formula:

49 (the chances of having a girl) – Mother’s age – Month of conception

An even number is a girl, and an odd number is a boy. So, what part does math play in this? Well, this is one of the few formulas that consider both the mother’s age and time of conception to some degree.In an example you would see:

- 49 – 19 – 1 = 29 a boy, Or
- 49 – 25 – 4 = 20 a girl, Or
- 49 – 30 – 9 = 10 a girl

These of course are fun ways to predict the sex of your baby while also being able to claim that you put your hard earned math and science skills to work.

To take the most direct approach, a betting person would look at the odds, right? A boiled down version of the overly complex probability formulas.

Okay, the natural odds are that for every 100 girls born, there are 105 little boys born . Why has nature decided this? Speculation is that it’s because men typically face many more dangers through their younger years. Historically, more men die in war than women. Historically, women live longer.

It’s likely that nature has a hand in offsetting the difference in life expectancy. From birth, without extenuating circumstances, these are the averaged life expectancies of both sexes.

## The Bayesian Analysis

This probability math formula uses the following wording and might take you back to the days of long word problems.

A large container has two children, assuming that there is an equal probability that either child is a boy or girl; there are three outcomes. Both are girls, both are boys, or there is one of each. From the primary problem here there are these outcomes:

- ¼ – chances of both being girls
- ¼ – chances of both being boys
- ½ – chances of one of each

But Bayes’ Theorem tries to accommodate that nature tends to favor baby boys, by using this math problem with the addition of assuming there is at least one boy.

What you end up seeing that is that the probability begins from fluctuating from the ¾ likelihood of two boys and then to 2/3 possibility of two boys when you remove the “at least” from the equation.

What does this mean for you? Let’s strip to this down to percentages as it’s easier to see a side by side comparison than fractions.

With the Bayes’ Theorem, there is somewhere between a 75% and 66% chance of a mother to have a boy assuming that nature favors boys. That’s a small window with a huge chance of having a boy! But it doesn’t accommodate for other known factors that impact the gender such as the parent’s age.

A more fun and straightforward way of looking at the odds is the Martingale Analysis. Are you a betting person? Willing to take a wager?

Imagine that you placed a bet that someone has two little boys, with fair odds, which means that your $1 bet will pay out for $4. Now, a gambler would know that the payout of one child being a boy and both children being a boy will have different odds. It is less likely that only one child will be a boy. Remember from the first part in the Bayes’ Theorem?

When one child is a boy, the first bet doubles, now you have $2. For a fair bet, the payout must double when the second child is also a boy, and that is how you get the $4 payout.

The $4 payout though changes the worth of your dollar to $1.33. When you remove the betting elements and break it down into odds again, you’re looking at 1 in 3 odds of both being a boy.

One formula with no scientific backing but purely for fun is this:

- Numerical representation of the month of conception + 1 = 1st number
- Age of the mother + 1 = 2nd number
- Add the above numbers together.

## For example:

8 (August) + 1=9
26 + 1=27
9 + 27= 36 – a boy!

If even, the baby is a boy. If it’s odd, the baby is a girl.

Another fun formula only uses the ages of the parents at the time of conception. This formula has some pull from the Chinese and Mayan calendar methods but has a little scientific background as well.

Because the age of the parents the probability of gender, it is not shocking to see math at work trying to support it.

This formula is really simple. Divide the number of years of each parent by 4, then whichever has the higher remainder, is the more likely gender.

- ¼ – chances of both being girls
- ¼ – chances of both being boys
- ½ – chances of one of each

## For example:

Mother’s age: 28/4 = 7

Father’s age: 30/4 = 7 with the remainder of 2.

From this example, the baby is likely a boy because the father had a remainder of 2.