How to calculate your Biological Prime Time – the time of the day you’re the most productive

Takeaway: Your “biological prime time” is the time of the day when you have the most energy, and therefore the greatest potential to be productive. To calculate yours, chart your energy levels for at least three weeks. Then schedule your most important, highest-leverage activities when you have the most energy.

Estimated Reading Time: 3 minutes, 37s.

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All day long your energy fluctuates around what you eat, how much caffeine you consume, how tired you are, how hard you work, and a whole lot more.

In an effort to calculate the exact time of day I’m the most productive (my “Biological Prime Time”, as coined by Sam Carpenter in his book Work the System), I recently charted my energy, focus, and motivation levels for 21 days, between the hours of 6am and 9pm. To control for any extraneous variables, I didn’t consume any caffeine or alcohol, worked out at different times every day, and woke up and fell asleep naturally.

Here are my results:

Energy Levels

My specific results aren’t too important, simply because yours will vary so much depending on your biology. But there are huge productivity benefits to charting your energy levels throughout the course of a typical day. I’ll go over those in a sec, but first, here’s how I recommend you chart your energy levels.

To chart your energy levels, I recommend a few things:

  1. Cut out caffeine, alcohol, and any other mood enhancers or depressants to get an accurate reading. This is a bitch, but absolutely essential in getting decent data. If you have a dependancy on caffeine, wait until you no longer feel withdrawal symptoms to chart your energy levels. As someone who depends on caffeine every day, this was the hardest part of charting my energy levels, but it was worth it in the end. Your energy levels have been shown to be quite steady throughout your life, so don’t worry–the data you collect will be good for a long time.
  2. Wake up and fall asleep naturally, without setting an alarm (if you’re able to, that is)
  3. Record your energy levels every hour, on the hour. I set up a Google Doc form to input my levels every hour on my phone (I also set up an hourly alarm), but a paper log works just as well. I charted my motivation and focus along with my energy, but I think energy is the most important element of the three, though I figured it couldn’t hurt to note the other two at the same time.
  4. Collect at least three weeks of data. Collecting the data is a pain, especially when you log it every hour, but the more data, the better your results will be. Three weeks of data will give you 21 data points for every hour of the day, which I think is a decent number to form conclusions from.

After you have finished logging your energy levels, you can then use them to become way more productive. By charting your energy levels (and focus and motivation levels, if you’re curious), you can schedule each day’s tasks based on when you have the most energy, focus, and motivation, and plan your entire day accordingly! You can also visually see interesting trends in your day, like how much of a morning bird or night owl you are.

Here are a few things that have worked for me, for scheduling around the peaks and dips of my typical day.

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Make the most of your energy peaks

  • Identify your biological prime time, and schedule accordingly. This is the time when your energy levels are the highest (along with your focus and motivation levels, if you chart them too, though they’re often highly correlated). Schedule your highest-leverage activities during this time, as well as your activities that require the most energy. Lately I’ve been scheduling my writing time and media interviews during this time, with awesome results. These are easily the activities that provide me with the greatest return, and so I naturally want to bring as much energy to them as possible. My biological prime times: 10am to noon, and 6pm to 8pm.
  • Pay attention to what you’re eating or doing. Energy spikes aren’t a good thing when they’re followed by a crash (like when you consume a lot of caffeine or sugar), but if they’re not, try growing the bright spots in your energy levels by picking apart what you eat or do to get such incredible energy.

Make the most of your energy dips

  • Recharge. I like to schedule naps and breaks during my energy dips. If you’re going to take a nap, why not make it when your energy tends to dip? Likewise, I highly recommend taking breaks when your energy dips so you can recharge. If you have the most energy at noon, why would you want to take your lunch break then instead of taking it when you actually need to refuel?
  • Do activities that require less energy and focus. I’ve recently made a point of scheduling my low-leverage activities, and activities that I need less energy for when my energy tends to dip. A few examples: checking email, sending out tweets, and reading.
  • Find a lasting energy boost. I like to drink green tea about a half hour before my energy dips, to help me ride through my dips on a wave of gently caffeinated green tea. (Plus, since most people don’t crash as hard after green tea, it helps me prevent energy dips later on.) Be wary of products that provide you with only a short-term energy spike, though, because you’ll often crash a few hours after consuming them.
  • Pay attention to what you’re eating. Often your energy dips because of sugary, unhealthy foods that spike your blood sugars. Be mindful of whether your energy dips are caused by what you eat.

Charting your energy levels over the course of a few weeks can be tedious, but the productivity gains you’ll get from doing so are impossible to ignore. Especially if you’re looking to dive deeper into how food, caffeine, and the time of the day impact your productivity, I highly recommend charting your energy levels.

  • Really interesting reading. I’ve noticed recently I tend to have a lot of energy late in the evenings and even going into and sometimes past midnight. I find myself getting really productive and concentrated around this time but, well, it’s just not a very sociable hour to be at my most energetic. I may use the chart you’ve recommended to confirm all this. But in the meantime I’m wondering whether you recommend a method for slowly adjusting the biological primetime.

    • Thanks a lot my friend! I’m not quite at the point where I’m making changes to my BPT yet; I think right now I”m primarily focusing on how I can embrace the BPT I have already. From what I’ve read it’s possible to artificially change your BPT (like with caffeine), but on the whole it’s relatively fixed, though it does change as you get older. That’s definitely a topic worth researching, though!

  • Really interesting reading. I’ve noticed recently I tend to have a lot of energy late in the evenings and even going into and sometimes past midnight. I find myself getting really productive and concentrated around this time but, well, it’s just not a very sociable hour to be at my most energetic. I may use the chart you’ve recommended to confirm all this. But in the meantime I’m wondering whether you recommend a method for slowly adjusting the biological primetime.

    • Thanks a lot my friend! I’m not quite at the point where I’m making changes to my BPT yet; I think right now I”m primarily focusing on how I can embrace the BPT I have already. From what I’ve read it’s possible to artificially change your BPT (like with caffeine), but on the whole it’s relatively fixed, though it does change as you get older. That’s definitely a topic worth researching, though!

  • This is a really fascinating experiment Chris.

    I did the same thing a year ago (and many other variables) in Excel. My main problem was that I found that after a while it got very hard to do the rating from 1-10. It’s hard to distinguish between a 6 and 7… And that’s going to ruin the results.

    I’m glad you were somewhat successful in doing this. I was not, I just ended wasting time tracking results that weren’t useful.

    • Thanks Ludvig! I found a similar thing: most of my results fell between 6-9, and there wasn’t much of a deviation between the numbers. I ended up adjusting the numbers to increase the deviation of the figures, so the results I picked apart at the end could be more concrete and meaningful. I definitely noticed a difference in my energy, focus, and motivation during the experiment, but it wasn’t reflected in the numbers because of a reporting bias..

  • This is a really fascinating experiment Chris.

    I did the same thing a year ago (and many other variables) in Excel. My main problem was that I found that after a while it got very hard to do the rating from 1-10. It’s hard to distinguish between a 6 and 7… And that’s going to ruin the results.

    I’m glad you were somewhat successful in doing this. I was not, I just ended wasting time tracking results that weren’t useful.

    • Thanks Ludvig! I found a similar thing: most of my results fell between 6-9, and there wasn’t much of a deviation between the numbers. I ended up adjusting the numbers to increase the deviation of the figures, so the results I picked apart at the end could be more concrete and meaningful. I definitely noticed a difference in my energy, focus, and motivation during the experiment, but it wasn’t reflected in the numbers because of a reporting bias..

  • Dan Erickson

    You lost me at cut out coffee. But I do see the logic in what you;re recommending. I have done this sort of thing in the past. The thing is. It doesn’t matter to me when I get things done as long as I do. And if I don’t, I don’t really care. Did you follow that logic. What I am interested in is alternative energy. I’me starting a new blog, http://www.hipdiggs.com and one topic I’d like to discuss is alternative energy.

  • You lost me at cut out coffee. But I do see the logic in what you;re recommending. I have done this sort of thing in the past. The thing is. It doesn’t matter to me when I get things done as long as I do. And if I don’t, I don’t really care. Did you follow that logic. What I am interested in is alternative energy. I’me starting a new blog, http://www.hipdiggs.com and one topic I’d like to discuss is alternative energy.

  • Cut out coffee? That would be pretty tough. Although I do like the idea of tracking energy levels to see when my peak performance is. Manually tracking it down the way you’re doing it would probably be the most effecient and accurate way to do it. You can try and just get a feel for it throughout the day, but that would be a little rough and might lead to some miscalculations. It would be interesting to see where I”m at. Generally I think my energy peaks after noon, but perhaps if I did this I would find different results.

    • Cutting out coffee was definitely the toughest part of the process, but when coffee masks your BPT so much, you pretty much have to! I think you hit the nail right on the head, you can get a rough feel of when you have the most energy, but when I personally looked at my results I was surprised with a lot of them, like how long it took me to get going in the morning. The only way to get a good reading is to manually track your measurements.

  • Cut out coffee? That would be pretty tough. Although I do like the idea of tracking energy levels to see when my peak performance is. Manually tracking it down the way you’re doing it would probably be the most effecient and accurate way to do it. You can try and just get a feel for it throughout the day, but that would be a little rough and might lead to some miscalculations. It would be interesting to see where I”m at. Generally I think my energy peaks after noon, but perhaps if I did this I would find different results.

    • Cutting out coffee was definitely the toughest part of the process, but when coffee masks your BPT so much, you pretty much have to! I think you hit the nail right on the head, you can get a rough feel of when you have the most energy, but when I personally looked at my results I was surprised with a lot of them, like how long it took me to get going in the morning. The only way to get a good reading is to manually track your measurements.

  • kamppila

    Thanks, this was very useful for me. I find it difficult to rely on a test that asks me for how I might’ve felt in the past weeks so I started tracking my energy, focus and motivation today. I changed the scale to 0-3 as that’s something I can measure better (0 no energy at all, 1 I have a little energy, 2 I have energy 3 I have energy to do anything) and it’s more actionable for me. I also put in the times I went to bed and woke up.

    • You’ll have to let me know how it goes! That’s a great idea, I had some troubles interpreting my data because I tended to rate most hours a 7 or an 8 on the scales. I normalized the data in the end to make it more valuable, but probably could have saved a lot of time with a simpler rating scale.

  • kamppila

    Thanks, this was very useful for me. I find it difficult to rely on a test that asks me for how I might’ve felt in the past weeks so I started tracking my energy, focus and motivation today. I changed the scale to 0-3 as that’s something I can measure better (0 no energy at all, 1 I have a little energy, 2 I have energy 3 I have energy to do anything) and it’s more actionable for me. I also put in the times I went to bed and woke up.

    • You’ll have to let me know how it goes! That’s a great idea, I had some troubles interpreting my data because I tended to rate most hours a 7 or an 8 on the scales. I normalized the data in the end to make it more valuable, but probably could have saved a lot of time with a simpler rating scale.

  • Sophie Oberstein

    Wouldn’t it be just as important to know your “prime time” taking into consideration all the givens in your life? That is, if I have to set my alarm clock for 6:30 to get to work on time, and I do drink a cup of coffee habitually each day at 3pm (I actually don’t), wouldn’t tracking your energy / focus / motivation levels still matter, maybe even more so, as that would represent where you have the most energy in an actual day, versus an ideal one?

    • I see where you’re coming from, but I think the purpose of calculating your BPT is to observe your body’s natural energy levels without outside stimulants, like coffee and tea, so you can rewire your behaviour to become more productive. For example, if you drink a huge coffee every morning, you might be masking the fact that you’re actually a night owl, and could become way more productive if you stayed up later and slept in (if you had the flexibility to do so). Or if you have a coffee every afternoon at 3pm, you could be keeping yourself up late when your body actually wants to wake up earlier so you can get more done in the morning.

  • Sophie Oberstein

    Wouldn’t it be just as important to know your “prime time” taking into consideration all the givens in your life? That is, if I have to set my alarm clock for 6:30 to get to work on time, and I do drink a cup of coffee habitually each day at 3pm (I actually don’t), wouldn’t tracking your energy / focus / motivation levels still matter, maybe even more so, as that would represent where you have the most energy in an actual day, versus an ideal one?

    • I see where you’re coming from, but I think the purpose of calculating your BPT is to observe your body’s natural energy levels without outside stimulants, like coffee and tea, so you can rewire your behaviour to become more productive. For example, if you drink a huge coffee every morning, you might be masking the fact that you’re actually a night owl, and could become way more productive if you stayed up later and slept in (if you had the flexibility to do so). Or if you have a coffee every afternoon at 3pm, you could be keeping yourself up late when your body actually wants to wake up earlier so you can get more done in the morning.

  • Matt Whyndham

    In doing a self reporting survey like this, what do you understand “Energy” to mean? And Focus and Motivation for that matter? Having clear criteria in mind could clean up the data considerably.

  • Matt Whyndham

    In doing a self reporting survey like this, what do you understand “Energy” to mean? And Focus and Motivation for that matter? Having clear criteria in mind could clean up the data considerably.

  • VerKl

    Very interesting. I’ve actually just started my own little experiment to see if building a workday according to my energy will work. So I’m first doing a 2 hour batch of very difficult tasks, then take a break, then a shorter batch and a shorter break until I reach 30 minute batches with 5 min breaks. You get the idea. I’m during week 2 now, and it seems to be getting the work done without me having to force my poor self to focus. Just now found the same thing described here. Do you think this approach has a future?

  • Ali

    Very interesting, thanks. I think this is a great starter, however I find some problems with this. Namely, how does one know what things affect one’s energy level? Shouldn’t one record their level of sleep per day, what they’re eating, if they’re exercising, the amount of water they’re consuming, whether they get into a fight with their significant other, etc. while at the same time, charting what you mentioned above? If so how would you recommend one go about charting those criteria as well?

  • Gośka Plichta

    hey, can you share with us your blank form for reporting levels? _please_

    • Here’s a simple app to help find your prime time on iOS: https://itunes.apple.com/us/app/body-prime-time-finder/id1123325785

      Full disclosure: I created the app for my self and decided to put it on sale as an experiment. :) It’s very simple for now, but I might add more features if people get interested.

      Personally I’d be interested to log events that lead to exceptionally high levels of energy, so I could try to do more of those things.

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