Understanding Intel iris graphic card spec for mac mini I'm reviewing moving to some software that has a system requirement of a 1GB of video / graphics card. 

The computer in question is a 2014 Mac mini, which I remember at the time of buying had a "Intel Iris Graphics" but no stated MB / GB number so I presumed it was a not very powerful graphics card built directly onto the CPU. 

Just now i checked "About this Mac" and it seems to state that the graphics card is "Intel Iris 1536MB" - Does that mean that I have a 1.5GB graphics card ? 

If so why doesn't apple list it as that, even now on the current mac mini page they list the graphic card as "Intel Iris Graphics" ?

Mac Mini Specs
The Intel Iris graphic chipset uses shared memory meaning it allocates up to 1.5GB (not 1.5Ghz which is frequency or more commonly known as speed) of RAM from the system to be used as VRAM.

So, If you have a Mac mini with 8GB of RAM, you really have a Mac mini with 6.5GB of usable RAM because 1.5GB was allocated to video.

From Apple's website:  Integrated Video on Intel-based Macs


  Apple computers using Intel Iris Graphics as the primary GPU dynamically allocate up to 1.5 GB of system memory. 


You were correct in your presumption - it's not a powerful graphics card built onto the CPU.

You should check with the vendor of your software to see if it has a requirement of 1GB of dedicated video memory (meaning it's built into the card and doesn't share with the system) or not.