Daylight Turnaround Calculator
Set the hour you must turn back — from your start time, sunset, estimated round-trip time, and a safety buffer — so a slow ascent never leaves you finishing in the dark.
Decide before the mountain decides for you
Most benightings do not come from bad weather but from a good day that ran long. Fixing a turnaround time before you set off turns a hard in-the-moment call into a simple clock check, and keeps summit fever from quietly eating your daylight.
Get the round-trip estimate this needs from the Hiking Time Calculator, and gauge whether the route is a realistic day at all with the Trail Difficulty Rating.
Frequently Asked Questions
What is a turnaround time?
A turnaround time is the hour by which you must head back regardless of whether you have reached your goal, so you can finish before dark. Mountaineers use it to take the decision out of the moment: agree the turnaround before you start, and you are far less likely to push on into the night because the summit is 'just a bit further'. This tool sets it before the midpoint of your usable daylight: by default the way back gets 25% more time than the way out, because tired legs and a careful descent slow most hikers late in the day. Set a larger allowance if your own hikes came back slower.
How does the safety buffer work?
The buffer is the margin you want to be off the trail before sunset — an hour is a sensible default. We subtract it from sunset to get your latest safe finish, then base the turnaround and the margin on that earlier time rather than on sunset itself. Increase the buffer for unfamiliar ground, tricky navigation, or a group that may slow down late in the day.
Why does the buffer end before sunset, not at dark?
Civil twilight after sunset still looks bright on open ground, but under trees, in a valley, or on rocky footing it is not usable hiking light, and a ridge to the west can hide the sun well before the official sunset. Take the sunset time for your hike date at the trailhead in local clock time (daylight saving included), and finish before the buffer runs out. Whatever the clock says, turn back early for weather: building storms, whiteout, or rising wind.
It says my plan is unsafe — what should I change?
An unsafe result means your estimated round-trip time runs past the latest safe finish. Options are to start earlier, pick a shorter or easier route, or accept a headlamp finish only if you are confident on the ground in the dark. Re-run the hiking time calculator to shorten the objective, and treat the warning as a prompt to plan, not a dare to risk it.
Do I still need a headlamp if the plan is safe?
Always. A margin can vanish to a twisted ankle, a navigation error, or a slow companion, and sunset comes fast in valleys and forest. Carry a headlamp with fresh batteries on every hike, tell someone your route and expected return, and know that the turnaround time is a planning aid, not a promise about the mountain.
Planning guidance only. A safe margin can vanish to an injury, a wrong turn, or bad weather. Carry a headlamp on every hike, share your plan, and use your own judgement over any calculated time.