I've read (read: glossed over, because it's largely irrelevant to most brewing) about ways to calculate diastatic power, but from what I gestalt, with modern highly modified malts, it doesn't take much base malt to convert most adjuncts. If you're wanting to be conservative, perhaps use some 6-row barley (which has more enzymatic power than 2-row).
Packaged: Fruitcake Old Ale
Primary: Simple Cyser '15
Secondary: Why do I keep this line here...?
Bulk Aging: Cocobochet, Wild Cider (2014 & 2015)
Planned: So many ideas, not enough time to brew them....