Knowing this simple technique — how to determine the hours of sunlight until sunset — will not only amaze your friends, but it could help you during any number of situations…such as estimating enough time to find (or make) shelter, time remaining to travel without the aid of artificial lighting, or give you the time to accomplish the tasks you need to before the sun sets (collecting firewood, starting a fire, making dinner, etc.).
For the geographical latitudes within the ‘lower 48’ of the United States, the following method can be used to approximate time remaining until sunset.
This method works for an average adult with an outstretched hand. Each finger will equal approximately fifteen minutes of daylight left, so four fingers will equal about one hour.
1. Stretch your arm out in front of you toward the sun. Bend your wrist so that your palm is facing you and your hand is horizontal with your thumb on top. The bottom of the sun should rest on the top of your index (pointer) finger.
2. Put your other outstretched hand below the first.
3. Now move your upper hand under the second and continue “walking” your hands down toward the horizon, counting the hands as your go.
The accompanying illustration shows four hours (sixteen fingers) of daylight left. Be sure to keep your arms straight as you slowly walk both hands down toward the horizon. It’s easy to get sloppy with this method by using only one hand or by putting your hand too close to your face because your elbows are bent.
Discovered this when reading Cody Lundin’s book, “When All Hell Breaks Loose”
This technique works in mid-latitudes, where most Americans live. But it is latitude dependent, and in the far north you’ll get more usable light than this suggests. And in the tropics, the sun sets “faster” because it is heading towards the horizon at a right angle.
The angular speed that the earth travels is the same for all of us: 360 degrees in 24 hours = 15 degrees per hour. But that speed appears differently along different paths depending on your geographical location. In the tropics the sun sets almost straight down into the horizon. In the far northern latitudes the sun approaches the horizon at a shallow angle.
You can customize this ‘rule of thumb’ or ‘rule of fingers’ to your own location and season (and how fat your fingers are). Measure the number of finger widths between the sun and the horizon and note the time. Then note the time at sunset. Where most Americans live, it will be around 15-18 minutes per finger.
Tip: Keep in mind situational awareness when hiking and estimating sunset. The canopy of the woods will hide alot of sunlight and it will get dark sooner than ‘sunset’. While it may not seem detrimental, when you’re talking about pre-dusk and walking in the woods it can get dangerous, and dark, very fast.