# The Structure of a Calculation

If you accidentally mistyped or misspelled a field name in the example above, you already know that FileMaker is a little picky about how you create a calculation. Clearly, syntax (the order of elements and the punctuation in your calculation) matters. Still, a calculation is really just text, arranged in a specific order. Here you learn the basic parts of a calculation through a couple examples.

### Note

Calculations are often called *calcs* for short, or *formulas*. Although there are some slight differences between a calculation and a formula, people usually use the terms interchangeably. Sometimes, a formula is so useful, or common, that FileMaker defines it as a reusable formula, also known as a *function* (see Functions).

A calculation can be short and simple:

Pi * Diameter

Or it can be more complicated:

Case ( Shape = "Circle" ; Pi * (Diameter/2) ^ 2 ; Shape = "Rectangle" ; ShapeLength * Width ; )

### Note

FileMaker won’t let you give a field the same name as an existing function. The field containing the length of a rectangular object has the unwieldy name “ShapeLength” to avoid confusion with FileMaker’s *length* function. The field name “Width” is fine, because there’s no width function.

In fact, calculations can be *really* long and complicated if you need them to be—up to 30,000 characters. Practically speaking, the only limit on the complexity of a calculation is your patience for creating it.

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