Day Scores

Sleep is good for staying healthy. For some of us, a simple count of how many hours of sleep we've had per night or per week does not provide sufficient context to make that number meaningful. For someone who has worked in technology, sometimes it's easier to make things more complicated in order to make them simpler.

I've heard recommendations of getting 7-9 hours of sleep per night. As sleep tends to come in 90-minute cycles, another recommendation I've heard is that we need 35 of those cycles each week whenever we can get them. (That works out to on average 7.5 hours of sleep per night.)

Let's assume an average of 8 hours of sleep per day is a good goal. That means a goal for waking hours is no more than 16 per day. For me, I find I feel best if I can keep that number to 15. (There are 15 hours in a day; the rest are for sleeping!)

A few years back I realized it would be fairly simple to create a formula that would compare waking hours to sleeping hours in a way that gives me a number that looks like a day counter.

24 evenly divides by 8, so if we assume 8 is the goal for sleeping, then an ideal ratio of waking to sleeping is 2:1. So, divide waking by 2 first, and then divide by sleeping, and one day would be equal to 1. That day score gives a very quick easy read on if I was trying to get too much out of a day or not.

Excel actually makes this really easy since it's measure of time is as a day being equal to 1. I use two columns, for rising and bed times, in Excel's standard time dateless format (bedtime being in 24-hour time), and then a third column to calculate the day score. Yesterday's formula on row 61 was this:

=((D61-C61)/2)/(C61+(1-D61))

If you subtract rising time (D61) from bedtime (C61), that's waking hours, divide that by 2, and then divide all that by the sum of morning sleep time (C61) and evening sleep time (1-D61), you get the day score.

Waking hours (D61-C61) / 2
----------------------------------------
Sleeping hours (C61+(1-D61))

Basic corresponding day scores:

• 10 hours of sleep; 14 waking hours = 0.70
• 9 hours of sleep; 15 waking hours = 0.83
• 8 hours of sleep; 16 waking hours = 1.00
• 7.5 hours of sleep; 16.5 waking hours = 1.1
• 7 hours of sleep; 17 waking hours = 1.21
• 6 hours of sleep; 18 waking hours = 1.50

If I'm up past midnight (which I try to avoid), I just put the bedtime in as the time + 24 on the hours. So, 12:30 AM goes in as 24:30. It works for the math, but not that visual as Excel shows that as 24:30:00. That visual incongruity helps drive home the point that I was up too late.

Recent examples:

Yesterday I got up at 7:40 (because I got to bed too late), and was down for the day at 10:14 PM (22:14 in Excel-speak). The day score for being up about 14.5 hours is 0.77.

Last Friday I got up at 5:30 (because I've been trying to get on a more even diurnal schedule), and went to bed at just before 9 PM at 8:54 (20:54). Day score = 0.9.

Those two low scores have been the exception recently. I've been getting up at an earlier time for the fall schedule, but due to a couple commitments and getting ready for other things also gearing up in the fall, my bedtime has not gotten correspondingly earlier. My current running day score total for the last 7 days is 10.84. If my ideal is 9 hours of sleep (which makes a 7-day total of day scores less than 6), this is not good.

After having used this system for several years now, I can tell you these scores and totals are very reliable indicators and predictors of if I can anticipate having health problems or other challenges soon or not.

Currently I'm in the red zone, so in order to keep my writing commitment, I picked an easy topic, so I could sign off for the night soon in peace. Hopefully I can get these numbers (my sleep quota) back into needed form soon.