Here is the EV equation for hero making a bet and villain calling or folding:
EV = fe*Pot +(1-fe)*(eq*(Pot + 2*Bet) - Bet)
where,
Pot is the pot before the bet
Bet is the bet amount and is the amount villain has to call (this can be modified if call < bet)
fe is the fold equity = Prob. villain folds
eq is hero’s win probability if villain calls
Assuming pot and 2 of the factors are known, to assure a positive EV, set the equation to zero and solve for the unknown third factor.
To see if betting is better than checking, set the equation to the EV check result and solve.
Of course, this assumes no raises or further bet action, so is most applicable for an all-in or closing river bet. I don’t know if such a calculator exists, but if you have Excel (or a comparable software) you can make your own by using its Goal Seek function or solve algebraically and have a cell with the appllicable equation.
The image shows part of such an application. It is much more than you need for a quick analysis, but it indicates what such an Excel program can do. It uses VBA code but that is not necessary.