# How To Use Calculation Fields in KPA EHS

Calculation fields let you use other fields in a formula to derive a new number.

For example, say you have a counter field called “quantity” and a numeric field called “price”. You could create a calculation field called “Grand Total” with the formula `quantity * price`.

## Overview

Here is a brief video overview of the basics:

Please watch the above video to understand the basics of calculation fields. Here are some more advanced examples.

## FUNCTIONS

Along with variables and simple math operators (like + and *), you can use functions like `round` as part of your formula. You can see a complete list of available functions here but the common ones are: abs, ceil, cube, exp, floor, log, log10, log2, max, min, pow, sqrt, square, random, sin, cos, and tan.

## Punch Clock

Say you had two Date/Time fields – both set up to track date and time. One called “Punch In” the other “Punch Out”.

Assign variable names to each field `punch_in` and `punch_out` – and now they can be used in a calculation. Create a new calculation field called “Hours”. Then edit the formula like this:

A date/time field will come in as the number of seconds since 1970. So `punch_out - punch_in` is the number of seconds between punch in and punch out. Then we divide by `60 * 60` which is the number of seconds in an hour. The calculation will now report the number of hours:

## Days Away From Work

Some reports need to calculate the number of days between two dates. So create two date fields, start and end, then subtract those two fields:

Here’s how that would end up looking:

## Overtime Hours

Let’s say you want a special field that shows overtime hours (anything over 8 hours). First you’d have a field where they’d enter total hours. This could be a numeric field, counter, or even a calculation based on a punch clock. In this example, we’ll use a numeric field. Then we’ll add a calculation field that uses a formula to show overtime:

This formula uses the `max()` function which evaluates to which ever number is larger. So if `total_hours` is less than 8, it will evaluate to 0. Here’s how it would look:

## Visibility Settings

Adding to the previous example, say we want a manager to sign off if there are 4 or more overtime hours. We can add a signature field that only shows up when necessary. First create the signature field and set it as required:

Now we’ll edit the Visibility of that signature field to only show up if “Overtime Hours” is 4 or more. So Edit the signature field and click the visibility tab. Now add a condition, choose “Overtime Hours”, set “4” as the minimum value, and press Continue. Now the signature will only show when necessary:

## Known Limitations

Many formula are possible with calculation fields, but the following are not currently possible:

• Using the calculation in association with Scoring
• Using calculation fields as a sub-field of counter fields
• Using counter sub-fields as variables in a calculation
• Using a select field’s value as a variable in a calculation