### Mathematical calculations with empty or non-numeric values

When doing any kind of mathematical calculations in formulas, all used values must contain a numeric value. If a field needed in the calculation does not yet contain a value, like when the entity is first created, a default value can be assigned to a variable with the `default` modifier.

{math equation="a+b" a=$field1|default:0 b=$field2|default:0}

Also, note that the value of a field might change during the execution from a previous formula and it’s extremely important to ensure the result is a valid numeric value. Most common errors happen when a formula results in a value with trailing whitespace.

### Division by zero error

Always ensure your formula does not result in division by zero. The easiest way to avoid this is by adding a condition around the calculation.

{if $my_field != 0}{math equation="a/b" a=1 b=$my_field}{else}1{/if}