You can use the Calculated value control to perform a calculation on a form, which will display on the form when it is used.
To watch an example of how to use the Calculated value control, we have a video of an online order form, which uses the calculated value control to calculate a line total, as well as the total amount for the order. This example applies to both Nintex Forms 2010 and 2013.
I had a tough time with the calculated fields until I realized how Nintex was using the fields. Big note here....You MUST use the named controls in order for it to use the values correctly. Took me way to long to figure that out. I will repeat, use the Named Control when calculating fields.
I'm glad I found your comments here Eric. I just could not think why the calculation was not working. But you put me on the right path. Thank you. An extra point here - the inputs for calculations should NOT be connected to list columns or the calculation will just not start.
Sometimes the 'logic' of Nintex Forms/workflow seems a little bizarre, still it's all an interesting learning curve.
For some reason as soon as I add another line item it won't calculate the line item total or the grand total. It calculates just fine if there is only one line though.
Care to share your formula? If it was working for one line, I'd think there may be a small glitch stopping it from updating for multiple.
Here is what you should have...
Your fields should be single line of text for Qty and Unit Price and a Calculated control for Totals. They should also be named controls as you stated, but put into a repeating section as one row. See above
Your item level total should have the formula as you are displaying it.
Your Invoice Total should have the following formula sum(Invoice Total)
Then when you add rows to the repeating section, it should automatically calculate those for you.
That's exactly what I had. I did change the 'recalculate formula on view mode' to yes and tripled check to make sure the calculated field was in the repeating section which it was. But I also made the the repeating section a little bit bigger so the 'X' wasn't overlapping the line item total field and now it is working. Maybe I just had the calculated field a little too close to the edge and wasn't in the repeating section?
Any idea why it does not calculate the total when the form is loading. It is just gives me zero, but when i change the row value it calculates the total for all the rows. I have the recalculate to "yes" for the three modes. I tried using form variables but didn't help.