Estimating time until sunset with your hand – and making camp in time

A finger at arm's length covers a small angle in the sky. For most people this angle is similar, because longer arms usually go with broader fingers – which is why the method also works for children. In the evening the sun sinks steadily towards the horizon. If you count the fingers in between, you know roughly how long it still needs.

How fast it sinks, however, depends on place and season. Near the equator the sun sets almost vertically, quickly and with a short twilight. In Central Europe it moves at a slant towards the horizon and needs longer for the same number of fingers; in the far north its path is very flat in winter. The rule of thumb 'one finger, a quarter of an hour' is therefore only a rough guide.

After sunset there is a twilight during which it stays light enough to see outdoors for a while. How long it lasts also depends on latitude and season. In forest and narrow valleys you often hardly notice this twilight.

Hold your arm fully stretched, hand sideways, fingers closed and horizontal, thumb tucked in. Put the bottom edge of your little finger on the horizon and stack the other hand above it until the top edge of your fingers covers the sun. That way you never look straight at the sun. Count the fingers.

Measure to the horizon behind which the sun will really disappear. In the mountains that is a ridge lying much higher than the flat horizon – there the sun disappears well before official sunset. If you have a watch, calibrate your hand on the first evening: note the number of fingers and the time, and repeat until sunset.

Plan backwards. Think about what you need before dark – a safe spot, a shelter, wood, water, warm clothes – and how long that takes. A shelter from natural materials often takes hours. If, for example, two hand widths remain, it is time to start making camp.

Never look straight at the sun – not even briefly and not with sunglasses. The eyes can be permanently damaged without it hurting. With the hand method, the top edge of your fingers covers the sun; you only squint past it to the side.

The biggest danger is overestimating the time left. Anyone who still wants to build a shelter, look for wood or find a way down at dusk makes mistakes, gets hurt more easily and gets cold. After sunset it cools down quickly. Plan generously, put on warm clothes before you get cold and always carry a headlamp.

The hand method makes sense when you have no watch or do not know the sunset time, and as a quick check on the way. Above all it helps with the decision 'go on or make camp?' – and in an emergency that decision is often more important than any navigation.

It does not work with thick cloud or fog. It is too rough for precise time planning. And anyone who looks up the sunset time before the trip and sets a turnaround time often does not need it at all.

Sunset and twilight times for any place and date can be found in calendars, weather services or at the U.S. Naval Observatory. In late autumn and winter the days are short where we live – many emergencies outdoors begin with people being surprised by darkness setting in early.

Bushcraft textbooks advise always building camp with plenty of daylight. Practise the hand method on evenings at home or on holiday and compare with a watch. After a few measurements you will know how much your fingers mean where you live in summer and in winter.