This was originally posted on the now-defunct Faith & Family Live in July 2013, and I've had people request links, so I'm reposting here.
Have you ever seen the hilarious post at Conversion Diary with the formula for parents to calculate their "sleep index" - how much sleep it feels like they've gotten in a night? (See it here.) It takes into account all sorts of factors, and comes up with a surprisingly accurate number.
After a particularly bad night I like to plug in all my own variables, and I'm always like, "Huh. Yup, feels about right."
So my engineer husband, who loves all things math-y and geeky, recently came up with a similar formula of his own. It's not as complicated as Jen's, but I think it holds up just as well.
He calls it Chaos Theory of Parenthood, and the idea is that there's a state when you have a number of kids of a certain age, where things are chaotic. You're swimming upstream during this time, just surviving, because having all these young children is physically overwhelming. And eventually things even out again, and you're out of Chaos Mode. (That's the point when a lot of families have another baby.)
Bryan came up with formula with his theory, and it goes like this: A family is in Chaos Mode when the average age of their children is lower than the number of their children. You can use simple year-number ages, or you can get more accurate and calculate months (dividing by twelve at the end, of course).
So right now our family has a 69-month-old, a 42-month-old, and two 14-month-olds. 69 + 42 + 14 + 14 = 139. 139 ÷ 4 = an average age of 34.75 months. 34.75 ÷ 12 = 2.9 years. 2.9 is considerably less than 4, the number of children we have, so we are still in Chaos Mode. (I could've predicted that!) The simpler version of our math is 5 + 3 + 1 + 1 = 10, 10 ÷ 4 = 2.5. 2.5 is close enough to 2.9, so it's still pretty accurate.
After further consideration, Bryan also came up with a corollary to his theory, which is: The greater the difference between the average age of children and the number of children, the more intense the Chaos Mode. So when our twins were newborns and the average age of our four children was 1.5 years, our state of chaos was more intense than it is now. (True.) With a little algebra, you can also figure out when your family will be released from Chaos Mode. My math* tells me that for us, it will be when Linus and Ambrose are about 2 years, 3 months old. That sounds about right. Only a year to go! Woo hoo!
(Note: now that it's July 2013, we have only a few weeks to go before we're out of Chaos Mode. I'm so excited!)
*55 + n + 28 + n + n + n = (4 x 4 x 12) = 192, 4n = 192 - 55 - 28, n = 27.25 months, or about 2.25 years, where n = the number of months that have passed since the twins' birth, 55 and 28 are the extra ages Camilla and Blaise were when Linus and Ambrose were born, and 4 is the number of our children and the average age they'll need to be to move out of Chaos Mode (times 12 because I'm calculating in months).