Using iPhone SIM in an iPad? Background - earlier this year, Verizon ran a BOGO sale where I was able to get an iPhone 8 for 'free', the catch being, I needed to add a new line of service. Given the bump from 3 lines to 4 was only $10, I took the deal. 

My question is as the title shows. I am looking to buy a new iPad Pro.



And from the spec page, it takes a Nano-SIM. The iPhone 8 I got shows this



Also a Nano-SIM. 

Are these cards interchangeable? Of course, I'm aware I'd need to buy the cellular Verizon compatible iPad, and am not expecting to be able to make calls from an iPad. Only internet access. 

I was just at an Apple store getting a battery update on my old 6, and asked this question. They told me 'no', but didn't really explain why. 

For what it's worth, I just finished a chat with Verizon, they said it wold not work - 



This is why I am here, hoping a member has already tried this. Whether it failed or not, I'd trust an answer here more than anything I get from Verizon.
It depends on the carrier. Generally, iPad SIMs from a carrier are so-called ‘data SIMs’ as they only provide the data service. A normal SIM can act as data SIM if the carrier supports it with an appropriate carrier bundle. You can speak to your carrier or see if anyone else has asked your carrier on a forum, e.g. UK's EE. That chat with Verizon appears like you're talking to a misinformed person — the SIM will easily fit, and the size difference of the iPad itself is obviously not a concern.