How to use calculations in your flow

Say you are selling garden tiles and beams. In this example we want to calculate the right tile quantity based on their preferred tile size and square meters. When a user says he prefers a 40x40cm tile and needs tiles for his 20 square meters terrace, we can store both inputs (40x40 and 20m2) in two separate variables. We can then use these inputs to calculate the right tile quantity. 

1. Enabling variables

We can use variables to create calculations. Variables can be used to store information that a user provide and show this information later in your flow or use the input in a calculation.

To start using variables we'll have to enable them first. You can do this under "Settings -> Configure -> Enable variables.

2. Adding the necessary variables in our flow

Let's start by adding the "tile_size" variable to each of the tile size answers. In the screenshot below, you can see that we have added a variable "tile_size" with value "40" for the tile size answer "40x40 CM". We repeat this for each of the other tile size answers. So we create a variable with the same variable name "tile_size" for the tile size answer "60x60 CM" but with the value "60". 

We have now set the first variable to store the correct tile size, based on a user choice. We also need to store the square meters of the user in a separate variable in order to calculate the right tile quantity based on the needed square meters and the preferred tile size. 

To do this, edit the (only) answer of the "Square meters" question and add a variable "square_meters" and check the "Use input" checkbox. The square meters user input will now be stored in the "square_meters" variable.

We have now created two variabels. 

1. tile_size  (selected tile size answer of user is stored as value > 40x40cm, 60x60cm, 100x100cm). 
2. square_meters (m2 input of user is stored as value).

We can now use both variables to calculate the right quantities for each product category (tile, beam and sand).  

Since the product sizes differ for tiles and beams, the quantity needed for each product category differs given the stated m2 of the user. Therefore, we have to separately calculate the quantities for the tiles and beams based on the user input. 

We create two additional variables: "quantity_tiles" and "quantity_beams" at the square meters question.

3. Create calculations based on the added variabels

Let's for example look at calculation for the "quantity_tiles" variable in the image above: {ceil((vars.square_meters*100)/vars.tile_size)}

In this calculation, we:

1. Take the previously defined "square_meters" variable and multiply it by 100 resulting in the total square centimeters. 
2. Next, we'll divide the total square centimeters by the tile_size variable defined in the previous "tile size" question. 
3. Lastly we'll round this calculation up with the ceil function.

For example: let's say a user wants a 60x60cm tile and needs 20 square meters of tiles. In this case the:

1. 'square_meters' value is 20 and it is multiplied by 100 to calculate the square centimeters. Resulting in 2000 square centimeters.  
2. The 2000 square centimeters is then divided by 60 (the selected tile_size). Resulting in 33.33 tiles. 
3. The result is rounded up with the ceil function. Resulting in 34 tiles. 

We do the same for the "quantity_beams" variable, but just using a little bit of a different calculation.

4. Using calculations in your flow

Variables and calculations can be used practically anywhere in your flow. For example, you can use a variable in the question text:

This results in the following:

5. Using calculations in your advise

Where it get's really interesting, is when you combine your product feed information with the calculated variables. 

For example, this allows you to calculate the correct price based on the amount of products calculated, edit your product title with the right quantity or use the variables to enrich your landing page with query parameters. 

To do this we'll have to enable "Calculated properties". You can do this under "Settings -> Feed -> Enable calculated properties".

Once we've enabled the calculated properties, you will see a calculator icon appear next to your mapping properties when you go to "Feed -> Mapping". 

5.1 Updating the product title to show the correct quantity of products

First, let's change our product title to show the correct quantity of products. Click the calculator icon next to the title property. 

As you can see, we can combine feed properties using the feed. prefix and variables using the vars. prefix.

Great! Let's check out the result so far. We can now see that the products advised contain the correct quantities in their titles.

Calculating the correct prices

First, let's make sure that the mapping for our price properties are correctly set to the "Number" type. You can find this under "Feed -> Properties".

Once that's done, head back to "Feed -> Mapping" and click the calculator next to the "Price" property. Use the correct variables and use the "feed.price" property to calculate the price. 

Awesome! If we preview the flow, we can now see that the calculated prices are also correctly displayed.