The following link is to a Battle Calculator that should work. I found it on the Internet, and fixed it. I also updated the shield strengths based on the recent unit updates.
To use it, you set your technology level. You then manually input the Power, Armour and Shield (PA&S) for the opponent’s unit. As I’ve said before, have a Scout or Corvette (“scout”) sneak to the enemy fleet and run through the attack sequence to get these AP&S values. Abort the attack and retreat the “scout.”
For added covertness, sneak the “scout” to a distant astro in the region, then move to the target astro (if possible). When you see the fleet strength, copy and paste the data into a blank document (e.g. Notepad) and retreat. When your scout is outbound, you can then fat-finger the data into the calculator.
One advantage of a Battle Calculator is that it allows you to test assumptions. For example, are Fighters more efficient than Bombers—or Frigates? (Answer, 1 FR costs 80, which is 16 FTs. In a same-tech battle, there will be 10 FTs remaining. Thus, FRs are inefficient.)
ACE Battle Calculator
Kahar’s Battle Calculator
KaHaR’s Battle Calculator is described by some as the preferred calculator. I’ve not used it, but one person said:
I use `KaHaRs because of it’s accuracy. For instance in the last battle I used it, it predicted I would end up with 8034.4 HCs out of 9000 and in the actual battle I had 8035.4 remaining at the end. That’s 99.9%25 accuracy.
AE Project’s Battle Calculator
Then there’s always AE Project’s Battle Calculator, which is online. It has some advantages. Over the years, there have been accusations that the site is malicious, but I’ve never noticed.