Height or Distance Calculation with a ruler (Biltmore stick)

Calculation of the height or distance of an object with the aid of a ruler. One value, distance or height, must be known or estimated. At length of the stretched arm from eyes to ruler, an average value (in cm) is set. For a better estimation, you should take your measure.
Biltmore stick:: A stick, or rather a ruler, is held with the hand outstretched, and the apparent height of the distant object is read from it. Using this value, the distance of the stick from the eyes, and the known or estimated height or distance, the other value is then calculated. If the stick is held horizontally rather than vertically, then the width can be estimated instead of the height.

Distance eyes-ruler a:		cm or in
Distance to the object b:		m or ft
Apparent height on the ruler c:		cm or in
Height of the object d:		m or ft

Please enter the apparent height and distance to the object or its height, the other value will be calculated.

The formula for the calculation is: d = b * c / a
So the values ​​are linearly dependent on each other, or in the case of the eye-ruler distance, inversely linear. This makes estimation easier, because, for example, half the apparent height of two objects of equal size means that the smaller object is twice as far away.

The specified value of 60 centimeters for the eye-ruler distance is an average value for normal-sized adults. This value can, of course, vary from person to person; children, in particular, generally have shorter arms.

The quality of such a measurement rises and falls with the accuracy of the initial value, the distance or height of the object. For the height of objects, you can work with experience values; for houses, for example, about three meters per floor. The distance can be determined using maps.

If you don't have a ruler, you can also use the thumb method. This cannot actually be used for heights, only for widths. However, you can tilt your head and thumb 90 degrees. If that is too uncomfortable for you, you can estimate a width that corresponds to the height to be measured.

Last updated on 07/01/2025. Author: Jürgen Kummer

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