How long before sunset should you start down a hike?
Plan to finish your descent by the end of civil twilight, about 25 to 40 minutes after sunset in open terrain at mid-latitudes, so leave the top at least your descent time plus a buffer before that. In forest or a deep valley, it gets dark sooner, so treat civil twilight as a ceiling, not a target.
The calculator above uses the formula leave the top = end of civil twilight − descent time − 15 minutes. It's deliberately simple so you can check it in your head. The sun maths is the NOAA solar position algorithm, run in your browser; nothing is sent anywhere.
Mini story: the ridge that ate twenty minutes
An invented example.
HikerSunset 4:41. Trail is 50 minutes up, 40 down. Leaving the car at 3:40, easy.
AsterfoldTonight the Sun sets at about 238°. Sun positions assume a flat horizon, so if a ridge sits on that bearing it will vanish early. Be up there with time to spare.
HikerSun went behind the ridge at 4:20. Glad we were up early. Watched the colour, headed down at 4:35 as planned, at the car by 5:15 with headlamps still in the pack.
AsterfoldRate what you saw in two taps? It goes in your field journal next to the forecast we saved before sunset.
Sunset hike questions
How long after sunset does it get dark on a trail?
In open country, civil twilight usually gives you roughly 25 to 40 minutes of usable light after sunset at mid-latitudes, longer further north and in summer. Under trees or in a valley it gets dark sooner. The calculator above shows tonight's civil twilight end for your city as an estimate.
What is civil twilight?
The National Weather Service defines the end of evening civil twilight as the moment the Sun's centre is 6 degrees below the horizon. Until then, in clear weather, you can usually make out the horizon and objects on the ground without artificial light.
When should I turn around on a sunset hike?
Before you start, pick a time to leave the viewpoint so that your descent ends by the end of civil twilight with a buffer to spare, and stick to it. The Washington Trails Association recommends setting a realistic turnaround time before you start and keeping it.
Do I need a headlamp for a sunset hike?
Yes. The National Park Service's Ten Essentials list includes illumination and recommends a headlamp because it is hands-free, plus spare batteries. A phone torch drains the battery you may need for navigation or a call.
Why does the sun disappear before the official sunset time?
Official sunset assumes a flat, sea-level horizon. A ridge, a tree line or buildings to the west hide the Sun earlier. Asterfold's Sun positions make the same flat-horizon assumption, which is why we tell you to check your real skyline.
Is this calculator accurate?
It uses the NOAA solar position equations in your browser, which are typically within a minute or two for sunset in open terrain. Treat the result as an estimate: terrain, trees, weather and your own pace matter more than the last minute of the maths.
