Calculation fields can be used to easily manipulate the data added to your apps. This very powerful tool not only allows you to perform mathematical calculations on the numbers in your app, but also lets you concatenate the values in certain fields together.
Values are added to a calculation field using variables. Use the "@" symbol to search for variables in your app. You can reference any fields within your app, as well as any fields within referenced apps.
Can't find a field you need? Save your app first and return to the template builder. This will happen for any fields you've just added to your app, since they technically do not exist in your app yet.
Use standard operators (+, -, *, /) to perform mathematical operations on numeric values. These should be separated by spaces (e.g. "Value1 + Value2", not "Value1+Value2").
You can add strings of text to your calculation as well. Text must be separated by quotations, and the "+" symbol should be used between text and variables (e.g. Value1 + " text goes here " + Value2).
Calculations will output data in one of three different types: Number, Date, or Text. The output type is determined the first time you create your calculation field. This is important to note, since the output type cannot be changed. If you try to change from one output type to another, you will see an error that says "The type of result changed from [X] to [Y]." To fix this, you simply need to delete the calculation field and recreate it to get a new output type.
Check out this video guide for a walkthrough:
If you'd like some assistance, you can check out this forum. There you will find examples of what other people have done, and if you can't find the answer to what you need you can post a new topic. Here is a general tip on how the calculations engine work for building good performing calculations.