Is there anything more difficult than having a night where sleep is not on the agenda for one or more of your kids? Wait, actually, there is: When the number of hours of sleep you technically got does not come anywhere near to representing the epic scale of your evening, and thus you do not receive the proper amount of sympathy from the people around you. “Oh, six hours, that’s not so bad,” your boss comments when you drag yourself into the break room for your fifth cup of coffee.

As a service to parents everywhere, I have used my own hours of wakefulness during the wee hours of the night to create a Sleep Index. Like how the Heat Index tells you what you need to know to properly complain about the weather, the Sleep Index allows you to articulate how tired you feel, regardless of the number of hours you were actually asleep. Here is the formula:

t = total hours elapsed from time you got in bed at night until the time you got up for the day in the morning (i.e. amount of sleep you should have gotten)

e = number of children who woke up in the night

h = number of hours actually up with the baby and/or other children

a = baby’s age in months (for older children, age in years; if multiple children woke up, age of oldest child)

s = how surprised you were that you were woken up (scale of 1-10, 10 = most surprised)

w = number of times you had to get up

c = total number of children you have

y = number of hours of sleep you got the night before

If it looks too overwhelming for your sleep-deprived brain, never fear! Below I’ll walk you through each step, using the hypothetical example of a woman named Jane who had a night like something out of a Homeric epic. (And yes, this is the kind of thing I think about when I’m up with the baby at 3am. Being a nerd is a 24/7 job.)

A. Take the total number of children you have, and divide it by three.

Jane has four kids, so her result is 1.3.

B. On a scale of 1 - 10, how surprised were you that you were woken up (10 being most surprised)? Add this to the total number of times you had to get up, and multiply that by two.

Jane’s kids usually sleep through the night, so she was quite surprised (a seven on our scale) when she heard her son yelling something about peanut butter and ants and his sheets in the middle of the night. This was only the beginning of the saga, and she would have to get up another time as well, twice in total. (7 + 2) * 2 = 18, so her result for this step is 18.

C. Take the age of the oldest child who woke up (in months if the child is younger than one), and divide it by three. Multiply that result by the total number of hours you were up with the kid(s).

Jane’s six-year-old daughter also woke up, so she’ll divide her age by two to get three. Jane was up a total of three hours, so her result for this step is 9.

D. Add the results of steps A, B, and C together, and divide that result by the number of hours of sleep you got the night before.

Jane stayed up late reading all the fabulous content at the National Catholic Register the night before, so she got about six hours of sleep. (1.3 + 18 + 9) / 6 = 4.7.

E. Multiply your result from step D by the total number of children who woke up during the night.

Between the peanut-butter-and-ants mixture on her son’s sheets and her daughter’s possibly-related nightmare, two of her children woke up. So this step gives her 9.4.

F. Subtract your step E result from the total hours that elapsed from time you got in bed at night until the time you got up for the day in the morning (i.e. amount of sleep you should have gotten).

Jane had gone to bed nice and early at 8:00pm to catch up on sleep, and dragged herself out of bed at 7:00am to get the kids ready for school, which means she should have gotten 11 hours of sleep. So her result for this final step is 1.6.

Thanks to this handy calculation, Jane is now prepared when people expect her to function at a level higher than an amoeba. When she tries to get out of a PTA meeting by telling the president lady about her insane evening, the president comments, “Well, you did still get eight hours of sleep, that’s not bad at all.” Now Jane is able to retort, “LISTEN, WOMAN, ACCORDING TO THE PARENTS’ SLEEP INDEX, I AM EFFECTIVELY FUNCTIONING ON LESS THAN TWO HOURS OF SLEEP!”

You’re welcome.