This calculator can be used to determine weapon Battle Values for BattleTech. It is based on the weapon BV calculations described on the Heavy Metal Pro Weapon Battle Value Calculation page, but it is a new implementation that adds some additional capabilities.
The set of weapons included in the selection box is nowhere near complete, but the JSON representation of the weapons can be edited to run the calculations with the stats of weapons that I haven't included or with custom weapon stats.
The Battle Value Calculation Options give you the ability to adjust the underlying calculations. For example, the official BV values for weapons align with a base to-hit number of 4 at short range, but the options can be used to adjust that up or down which will change the BV pricing for to-hit modifiers.