If your formulas are simple and straight forward you can get away with re-using bits and pieces in multiple formulas, but you notice that things can get confusing quite fast! We have created Variables to make sure your head won't explode while building a calculator with complex calculations.

# How do Variables work?

Variables act in exactly the same way as Formulas. The only difference is that they aren't visible on your calculator. Instead of showing Variables directly to your visitors, you use variables in other Formulas.

# Example

Let's say you have a ROI calculators which calculates "extra revenue", "extra profits" and "return on investment" for you customers. Your product costs $ 1000,- and you have the following questions:

- QA: How much traffic do you have on your website?
- QB: How much is margin do you get on your product?

You assume that you can bring in $ 2,- in revenue for every website visitor.

## Variables

First you will need to make a variable called "VA: Extra Revenue". This will look like this:

```
QA * 2
```

Now you have the "Extra Revenue" variable, you create another variable called "VB: Extra Profits". The formula looks like this:

```
VA * QB
```

Now the formulas look like this:

- Extra Revenue:
`VA`

- Extra Profits:
`VB`

- Return on Investment:
`VB - 1000`