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

by | Dec 12, 2013 | Energy

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.

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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.


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.

Written by Chris Bailey

Chris Bailey has written hundreds of articles on the subject of productivity and is the author of three books: How to Calm Your Mind, Hyperfocus, and The Productivity Project. His books have been published in more than 40 languages. Chris writes about productivity on this site and speaks to organizations around the globe on how they can become more productive without hating the process.

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