For this project we will always record shadow lengths as a percentage. If a shadow is twice as long as the height of the object that made the shadow, we would record the shadow length as 200(%). If the shadow is half as long as the height of the object, we would record that as 50(%).


Calculating the percentage of an objects height its shadow represents can be done easily using a simple formula. All you need is the length of the shadow and the height of the object. The units don't matter, so long as both measurements are done in the same units. To determine the percentage divide the length of the shadow by the height of the object and multiply the result by 100. (See below)

Let's take a couple of examples. Suppose your friend is 120 cm tall and when you measure it, the length of her shadow is 47 centimeters. Dividing 47 by 120 gives 0.39 and multiplying that by 100 gives us 39%. (See below)

Now imagine you take a glue bottle outside and measure its shadow. Let's say the height of the glue bottle is five and a half (5.5) inches and the shadow turns out to be two and a half (2.5) inches. We divide 5.5 by 2.5 and get 2.2, which, when multiplied by 100 gives us 220%. (See below)


You can use the calculator below to determine the percentage of the object height represented by the shadow length. Just make sure both measurements were made using the same units.

Swiffy Output