# Calculate Question Type

**Last updated:**
<a href="https://github.com/kobotoolbox/docs/blob/511ea4cb3c698a4b45e7c2b4efd1af4e356e811f/source/calculate_questions.md" class="reference">15
Feb 2022</a>

Some advanced forms may require an internal calculation to take place as part of
the form (rather than afterwards during the analysis). This can be done by
adding a Calculation and writing the mathematical expression into the question
label field.

![image](/images/calculate_questions/calculation.gif)

A mathematical expression could be as simple as `5 + 1`, but most likely it
would include reference to another question.

Referencing other questions in your calculation question requires giving other
questions fixed names through the question settings, such as `girls` or
`income`. When referencing those questions, you should always use the unique
question name (not label) - `${girls}` or `${income}`

For example, if you want to convert the answer to a question about someone's
income into another currency (such as Rwandan Francs to US Dollars), you should
write `${income} div 688`.

You can also use the answer to this Calculate question for other purposes, such
as building your skip logic (for example only ask a follow-up question above a
certain income threshold) or by displaying it inside a Note
([see here](responses_inside_question.md) for help on how to display the
response to one question in the label of another question).

## List of available functions

There are a lot of different options available, such as the round() function
(e.g. `round(${int_1} div ${int_2}, 1`) will round the result of a division to a
single decimal). For a list of some of the many mathematical expressions that
can be used in this field, please see
[XForm specifications on calculation functions](https://docs.getodk.org/form-operators-functions/)
for the technical background of all the functions available in KoboToolbox and
XLSForms. For advance use of calculations in KoboToolbox, please refer to
[this article](advanced_calculate.md).

## List of available math operators

| Operator               | Description                  |
| :--------------------- | :--------------------------- |
| `+`                    | Addition                     |
| `-`                    | Subtraction                  |
| `*`                    | Multiplication               |
| `div`                  | Division                     |
| `=`                    | Equal                        |
| `!=`                   | Not equal                    |
| `<`                    | Less than                    |
| `<=`                   | Less than or equal to        |
| `>`                    | Greater than                 |
| `>=`                   | Greater than or equal to     |
| `or`                   | Or                           |
| `and`                  | And                          |
| `mod`                  | Modulus (division remainder) |
| `pow([base], [power])` | Power / exponent             |