The recipe builder already tells you how many IBU's a particular addtion will contribute, but I would like to enter the desired IBU and have it yield how many grams/ounces to yield that. That sure would be a helpful tool in building a beer to specs

cheers,
Jackson

i would like this feature with a further specification;

Make the reverse IBU only work on bittering hops (120 to 60 min additions).
The reasoning is that many brewers only give you the IBU of the bittering addition of their beer,
everything else is just bonus.

In my opinion reverse IBU is useless without this little specification. If you are not to make the reverse ibu calc atleast give some manual mechanic to dial in the wanted IBU without typing in numbers (hint: up-down arrow action or mouse scroll or something, dont make a dropdown menu thats horrible).

Cross referencing with idea of entering grains as percentages:
www.brewersfriend.com/forum/viewtopic.php?f=7&t=430

I don't see any new action on this question of a reverse IBU calculations. For any Boil kettle hop addition if you could set a "Goal for IBU" just like you can for the "Goal for OG" in fermentables it would be a big help. The "Goal for IBU" could be either a % of the IBU or an actual IBU target. My homemade spreadsheet I set up to do this and found it very helpful. Here is an example. I set the % of the IBU I want for each hop addition in the boil kettle. Then on my calculation I set the Target IBU I want, say and IBU of 40 and then It would calculate how many grams of each hop I need to get the assigned % of IBU.

This would be a great help. I know how to do the calculations manually, but it seems weird that's not the default entry since with bittering and flavoring hops the weight is not usually what brewers work off of.