You can use the following smart fields in your templates to do maths operations:

**addition**– addition**sub**– subtraction**mul**– multiplication**div**– division**intdiv**– integer (floor) division**abs**– absolute value**mod**– modulo

## Examples:

`{{ 17|sub:13 }}`

would return `4`

(because 17 minus 13 equals to 4)

The following is a complex example combining math operations on the balance of the invoice attached:

{% with invoices.0.balance|mul:0.01|floatformat:2 as variable_interest %}

{% with invoices.0.balance|addition:10 as interest_fixed %}

The 1% variable interest is: ${{ variable_interest }}

The $10 fixed interest is: ${{ interest_fixed }}

The total interest is: ${{ variable_interest|addition:interest_fixed }}

{% endwith %}

{% endwith %}

First line: applying 1% on the balance of the invoice, and ensuring a rounding to 2 decimals in a variable `variable_interest`

Second line: applying $10 fixed interest rate

Fifth line: adding both variable and fixed interests

If the invoice balance is $4200, then the final result of the example above would be:

The 1% variable interest is: $42.00

The $10 fixed interest is: $4,210.00

The total interest is: $4,252.00