Hyperdeck Studio Mini File Sizes

Looking to purchase an SD card ahead of my mini arriving Thursday.

Will be recording 2160p30, and hoping to get about 1hr30min tops. What size should I be looking for?
Would 64gb cover it, or do I need 128gb? Or more?

Ben which codec you want to record in?

There is an APP called AJA Datacalc. With this software you can select the codec you want to use.
Set the number of channels of audio. (16 with the hyperdecks)
And then you can see how much time you can record on a card or how much GB it takes to record a time frame.
AJA DataCalc for IOS
AJA DataClac for Andriod

Also remember that you need a card that is recommended and tested by BMD. Other cards might not work due too read write speeds..
What SD card should I use with the Blackmagic Video Assist 4K?

Thanks Daniel! Really useful app-- looks like ProRes Proxy is the only one that will get me onto one card (estimated at 115gb, so 128gb it is), though putting a 64gb in slot 2 seems like a wise decision.

Thanks again for the help. Any idea if anyone has found a 256gb or 512gb card that can do the UHS-II rates the mini needs reliably? The accepted list only has 128gb max under the UHD section.