Find the latest safe turnaround time for any hike.
Turnaround Calculator
Check it for your location on the day you are walking. Any weather app shows it, and it is the one number this calculator cannot work out for you.
No signal? Estimate it from latitude and month
About 18:14 in local solar time, calculated from the sunset hour angle, with the sun's declination taken from Cooper's 1969 approximation rather than from an ephemeris. That approximation is good to a few tenths of a degree, which is worth minutes at the solstices and more at high latitude. Clock time differs again: a timezone is up to an hour wide either side of its meridian, and daylight saving adds another. Treat it as a sanity check, not a sunset table.
Safe Turnaround
16:00
Safe to go
Turn around at 16:00
Back by 19:00 · Sunset 20:00 · 60 min buffer
Always tell someone your planned turnaround time before you leave. Stick to it; conditions can change. When in doubt, turn around early.
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For reference only. This calculator provides an estimated turnaround time based on Naismith's Rule. Actual hiking speed varies significantly with terrain, weather, fitness, pack weight, and group size. Always add a safety buffer. Getting caught out after dark in the mountains is dangerous. Check sunset time and weather forecast before every hike.
Sources: The rule comes from a note in the Scottish Mountaineering Club Journal, 1892: no paper was published under the name Naismith's Rule. The descent correction this calculator applies is Eric Langmuir, Mountaincraft and Leadership (1984), and the pace correction is undefined's.
Mountain search and rescue (SAR) statistics consistently show that a large proportion of incidents involve hikers caught out after dark. Night hiking dramatically increases the risk of falls, navigation errors, and hypothermia from unexpected exposure.
The turnaround discipline
Experienced mountaineers and SAR professionals emphasise the turnaround time as a non-negotiable commitment, not a suggestion. The trap is summit fever: the temptation to push on when you are close to the top, even when your plan says turn back.
Plan before you leave: Calculate turnaround time at home, not on the mountain
Tell someone: Share your planned turnaround and return times with a contact
Stick to it: When turnaround time arrives, turn around. No exceptions.
Early is always safe: Arriving back at the car 2 hours early has no downside
The summit will still be there next time. The mountains will not renegotiate your turnaround time.
How to Calculate Turnaround Time
The turnaround time formula works backwards from sunset. You know when the sun sets, how long your total hike takes, and how much buffer you want. Everything else follows from those three numbers.
The formula
Turnaround = Sunset - (Hike time ÷ 2) - Buffer
This assumes the second half of the hike takes the same time as the first half. In practice, the return is often slower due to fatigue, so the buffer accounts for this.
Choosing your buffer
30 min: Minimum buffer for short, well-marked routes in good conditions
60 min: Standard buffer for most day hikes (recommended default)
90 min: Remote routes, unmarked terrain, early season, or group hiking
The sunset time is yours to supply, because it depends on latitude and date and this calculator cannot know where you are. Check it in a weather app on the day. If you have no signal, the estimator in the widget works it out from latitude and month using the sunset hour angle, in local solar time.
The 50% Rule
The 50% rule is a practical safety principle: if you have not reached the halfway point of your route by your planned turnaround time, you must turn around, even if you are not at the midpoint.
Why this works
Hiking speed varies. If you are moving slower than planned, waiting until you reach the halfway point physically means you will be out after dark. The turnaround time is a time constraint, not a distance constraint.
Calculate turnaround time based on total expected hiking duration
When that time comes, turn around, regardless of where you are on the route
A slower-than-expected outward leg means your return will also be slower
No exceptions for "being so close to the top"
Building in the habit
Set an alarm on your watch or phone for your turnaround time before you start. When it goes off, you turn around. This removes the emotional decision-making from the equation and makes safety automatic.
"Getting to the top is optional. Getting back is mandatory." Ed Viesturs, first American to summit all 14 eight-thousanders.
Turnaround is sunset, minus half your planned hiking time, minus the buffer you choose. Nothing else goes into it. For a six hour walk with sunset at 17:30 and an hour of buffer, that is 17:30 minus 3:00 minus 1:00, so you turn round at 13:30 wherever you have got to.
Half the time rather than half the distance, and that is deliberate. The way back is usually quicker on the same ground, but you are more tired, the light is worse and the day has already taken something out of you. Splitting on time absorbs all of that without needing to model any of it.
The word turnaround is doing real work here. It is not a target and not a plan, it is a time at which you go back regardless of how close the summit looks. That is the whole value of setting it before you leave, while nobody is invested in the top.
Why the calculator asks you for the sunset time
Because sunset depends on latitude and date, and this page does not know where you are.
A single time per region cannot stand in for that, however carefully the regions are drawn, because region is not what determines sunset. One figure for North America has to cover Alaska and Florida: 20:30 in June is roughly right near 40 degrees and hours wrong at Denali. One figure for Northern Europe has to cover southern Sweden and northern Norway, where in June the sun does not set at all. Stockholm in December sets near 14:50, an hour and a half before Rome. An hour of error in a turnaround time is a night out.
So the sunset time is an input. Any weather app gives it for your location on the day, which takes ten seconds and removes the entire class of error. If you are out of signal, the estimator inside the widget calculates it from latitude and month with the standard sunset hour angle, the same formula any almanac uses, and tells you what it is: local solar time. Clock time differs from it, because a timezone is up to an hour wide either side of its meridian before daylight saving is added. It also knows what the table could not express, and says so: inside either polar circle there are months with no sunset to calculate from, June in the north and December in the south, and months with no sunrise either.
The 50 percent rule, and where it breaks
Turn round when half your available time is gone, not when half the distance is. On an out and back route with a fixed finish time, that is the rule this calculator applies, and it is the one that survives contact with a long day.
It assumes the way back retraces the way out. Three shapes break that assumption, and on all three the calculator is giving you a number for the wrong route. A loop commits you: past a certain point the shortest way home is forward, and the turnaround stops meaning anything. A traverse finishing somewhere else has no turnaround at all, only a schedule. And a route whose descent is a different line from the ascent, which is common on scrambles, can take longer coming down than going up.
For those, plan against fixed checkpoints instead: a time by which you must be at the col, at the hut, at the top of the descent. Same idea, applied to places rather than to the halfway mark.
How much buffer to leave
An hour for a normal day hike on a path you can follow. Thirty minutes only for short, familiar ground you could walk in the dark. Ninety minutes for remote or unmarked routes, difficult navigation, winter, or a group whose pace you cannot predict.
Where these numbers come from
They are ours. No standard or published guideline sets a safety buffer for a day walk, and we have not found one to cite, so 30, 60 and 90 minutes are this site's conservative convention rather than figures anyone certified. What is behind them is arithmetic you can check: an hour of buffer is roughly the time it takes to lose and refind a path in poor light, or to deal with one twisted ankle in a party of two. They are a floor to build on, not a permission to cut it fine, and the right buffer for ground you know is the one experience tells you.
Two things the buffer is not. It is not contingency for being slower than planned, because that is already handled by the hiking time you entered. And it is not darkness insurance: sunset is not the same as dark, but the useful light after it is short, drops fast in forest and in a valley, and disappears entirely under cloud. Carry a head torch whatever the buffer says.
Frequently asked questions
What is a turnaround time in hiking?
A turnaround time is the latest point in your hike where you must reverse direction and head back to the trailhead to return safely before dark. It is calculated by subtracting half the total hiking time and a safety buffer from sunset. Setting a firm turnaround time before leaving and respecting it is the single most important hiking safety practice. Most mountain rescues happen because hikers continued past the point of safe return.
How do I calculate the latest safe turnaround time?
The formula is: turnaround time = sunset time - (total hiking time ÷ 2) - safety buffer. For a 6-hour hike with a 17:30 sunset and 60-minute buffer: 17:30 - 3:00 - 1:00 = 13:30. You should be back at the trailhead by approximately 16:30, giving one hour before sunset. Enter the sunset time for your location and the calculator applies the formula.
What safety buffer should I add to my turnaround time?
A minimum 30-minute buffer is suitable for experienced hikers on familiar trails in good conditions. A 60-minute buffer is appropriate for most recreational hiking; it accounts for unexpected delays, wrong turns, and fatigue. A 90-minute buffer is recommended for mountain routes, unfamiliar terrain, groups, or when weather may deteriorate. The buffer also ensures you have sufficient light for route finding and photo stops on the way back.
What is the 50% rule in hiking?
The 50% rule states: if you have not reached the halfway point of your planned route by your turnaround time, you turn around, regardless of how you feel or what you can see ahead. This rule prevents summit fever from overriding the rational decision to turn back. It is especially important on out-and-back routes where the return leg takes as long as the outward leg.
Should I always stick to my turnaround time?
Yes. The turnaround time should be treated as a commitment, not a suggestion. The most common mountain accident scenario involves a hiker who felt strong, continued past the turnaround, reached the summit, and then descended in darkness on unfamiliar terrain. Descending in darkness on rocky or steep ground significantly increases the risk of falls. Tell someone your turnaround time before you leave and honour it.
What happens if I do not have enough daylight for my planned hike?
If the calculator shows insufficient daylight, your options are: start earlier that day, choose a shorter route, or postpone to a day with longer daylight. In autumn and winter, many mountain routes require pre-dawn starts to complete safely. Never attempt a route that the calculator flags as unsafe on the grounds that you are fast or the weather is good. Conditions can change rapidly in the mountains.
How do I find sunset time for my hiking location?
Check a weather app, which shows sunrise and sunset for wherever you are, and do it for the day you are walking rather than today. This calculator asks you for that number instead of guessing it, because sunset depends on latitude and date: at 45 degrees north it falls near 20:00 solar time in June and near 16:20 in December, at 45 degrees south those two months swap over, and inside either polar circle there are months when it does not happen at all. If you are already out of signal, the estimator inside the widget calculates it from latitude and month using the standard sunset hour angle, in local solar time, which is close enough to sanity check against but is not clock time.
Should I carry a headlamp even if I plan to return before dark?
Yes, always carry a headlamp. Unexpected delays (injury, navigation error, helping another hiker) can mean returning after dark despite good planning. A headlamp weighs 80 to 100g and takes up minimal pack space. Most mountain rescue incidents that occur after dark involve hikers who did not carry a light because they planned to be back before sunset. A headlamp is non-negotiable safety equipment on any route over 3 hours.